| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Sean Christopherson | 5499 | 18.58% | 303 | 27.08% |
| Paolo Bonzini | 4993 | 16.87% | 118 | 10.55% |
| Xiao Guangrong | 3296 | 11.14% | 103 | 9.20% |
| Avi Kivity | 2617 | 8.84% | 101 | 9.03% |
| David Matlack | 2529 | 8.55% | 55 | 4.92% |
| Marcelo Tosatti | 1543 | 5.21% | 40 | 3.57% |
| Junaid Shahid | 1143 | 3.86% | 32 | 2.86% |
| Chao Peng | 870 | 2.94% | 4 | 0.36% |
| Takuya Yoshikawa | 764 | 2.58% | 34 | 3.04% |
| Lai Jiangshan | 704 | 2.38% | 34 | 3.04% |
| Ben Gardon | 614 | 2.07% | 37 | 3.31% |
| Joerg Roedel | 489 | 1.65% | 20 | 1.79% |
| Izik Eidus | 335 | 1.13% | 7 | 0.63% |
| Vitaly Kuznetsov | 322 | 1.09% | 15 | 1.34% |
| Eddie Dong | 296 | 1.00% | 8 | 0.71% |
| Peter Xu | 254 | 0.86% | 10 | 0.89% |
| Mingwei Zhang | 251 | 0.85% | 6 | 0.54% |
| Kai Huang | 246 | 0.83% | 8 | 0.71% |
| Yang Zhang | 187 | 0.63% | 1 | 0.09% |
| Wei Huang | 171 | 0.58% | 2 | 0.18% |
| Wanpeng Li | 164 | 0.55% | 4 | 0.36% |
| Gleb Natapov | 159 | 0.54% | 7 | 0.63% |
| Huaitong Han | 156 | 0.53% | 1 | 0.09% |
| Brijesh Singh | 127 | 0.43% | 2 | 0.18% |
| Michael Roth | 127 | 0.43% | 2 | 0.18% |
| Andrea Arcangeli | 115 | 0.39% | 3 | 0.27% |
| David L Stevens | 114 | 0.39% | 4 | 0.36% |
| Zhao Yan | 103 | 0.35% | 2 | 0.18% |
| Hou Wenlong | 102 | 0.34% | 7 | 0.63% |
| Keqian Zhu | 85 | 0.29% | 2 | 0.18% |
| Yu Zhang | 81 | 0.27% | 2 | 0.18% |
| Lan Tianyu | 79 | 0.27% | 4 | 0.36% |
| Jiří Paleček | 76 | 0.26% | 1 | 0.09% |
| Peter Feiner | 73 | 0.25% | 3 | 0.27% |
| Xiantao Zhang | 64 | 0.22% | 9 | 0.80% |
| Nadav Har'El | 53 | 0.18% | 2 | 0.18% |
| Yosry Ahmed | 53 | 0.18% | 1 | 0.09% |
| Liang Zhang | 48 | 0.16% | 1 | 0.09% |
| Huang Ying | 41 | 0.14% | 2 | 0.18% |
| Maxim Levitsky | 40 | 0.14% | 5 | 0.45% |
| Maciej S. Szmigiero | 34 | 0.11% | 2 | 0.18% |
| Nadav Amit | 31 | 0.10% | 3 | 0.27% |
| Wei Yang | 28 | 0.09% | 2 | 0.18% |
| Feng Wu | 25 | 0.08% | 3 | 0.27% |
| Alex Williamson | 24 | 0.08% | 1 | 0.09% |
| Dor Laor | 23 | 0.08% | 1 | 0.09% |
| Radim Krčmář | 23 | 0.08% | 1 | 0.09% |
| Vipin Sharma | 21 | 0.07% | 3 | 0.27% |
| Miaohe Lin | 20 | 0.07% | 3 | 0.27% |
| Xiaoguang Chen | 20 | 0.07% | 1 | 0.09% |
| Like Xu | 17 | 0.06% | 3 | 0.27% |
| Arnd Bergmann | 16 | 0.05% | 2 | 0.18% |
| Kazuki Takiguchi | 15 | 0.05% | 1 | 0.09% |
| Hamza Mahfooz | 15 | 0.05% | 1 | 0.09% |
| Sheng Yang | 14 | 0.05% | 4 | 0.36% |
| Gerd Hoffmann | 14 | 0.05% | 1 | 0.09% |
| Jason Baron | 13 | 0.04% | 1 | 0.09% |
| Mario Smarduch | 13 | 0.04% | 1 | 0.09% |
| Andre Przywara | 12 | 0.04% | 2 | 0.18% |
| Li zeming | 12 | 0.04% | 1 | 0.09% |
| Ingo Molnar | 11 | 0.04% | 5 | 0.45% |
| Tom Lendacky | 10 | 0.03% | 4 | 0.36% |
| Dave Hansen | 10 | 0.03% | 3 | 0.27% |
| Andres Lagar-Cavilla | 9 | 0.03% | 2 | 0.18% |
| Jan Kiszka | 8 | 0.03% | 4 | 0.36% |
| Bandan Das | 8 | 0.03% | 3 | 0.27% |
| Eric Northup | 8 | 0.03% | 1 | 0.09% |
| Ben-Ami Yassour | 7 | 0.02% | 1 | 0.09% |
| Rick Edgecombe | 7 | 0.02% | 3 | 0.27% |
| Wei Yongjun | 7 | 0.02% | 1 | 0.09% |
| Mohammed Gamal | 6 | 0.02% | 2 | 0.18% |
| Thomas Gleixner | 6 | 0.02% | 3 | 0.27% |
| Jay Zhou | 6 | 0.02% | 1 | 0.09% |
| Chenyi Qiang | 6 | 0.02% | 1 | 0.09% |
| Wei Wang | 6 | 0.02% | 1 | 0.09% |
| Eric W. Biedermann | 5 | 0.02% | 2 | 0.18% |
| Zhao Jin | 5 | 0.02% | 1 | 0.09% |
| Jim Mattson | 5 | 0.02% | 2 | 0.18% |
| Jike Song | 5 | 0.02% | 1 | 0.09% |
| Haozhong Zhang | 4 | 0.01% | 2 | 0.18% |
| Shaoqin Huang | 4 | 0.01% | 1 | 0.09% |
| Binbin Wu | 4 | 0.01% | 1 | 0.09% |
| Hillf Danton | 4 | 0.01% | 1 | 0.09% |
| Borislav Petkov | 4 | 0.01% | 1 | 0.09% |
| Davidlohr Bueso A | 4 | 0.01% | 1 | 0.09% |
| Dominik Dingel | 4 | 0.01% | 1 | 0.09% |
| Christophe Jaillet | 4 | 0.01% | 1 | 0.09% |
| Paul Gortmaker | 4 | 0.01% | 1 | 0.09% |
| Andrew Honig | 3 | 0.01% | 1 | 0.09% |
| Uros Bizjak | 3 | 0.01% | 1 | 0.09% |
| Eduardo Pereira Habkost | 3 | 0.01% | 1 | 0.09% |
| Rusty Russell | 3 | 0.01% | 1 | 0.09% |
| Tanzir Hasan | 3 | 0.01% | 1 | 0.09% |
| Anthony Liguori | 3 | 0.01% | 1 | 0.09% |
| Hannes Eder | 3 | 0.01% | 1 | 0.09% |
| Li RongQing | 2 | 0.01% | 1 | 0.09% |
| Joe Perches | 2 | 0.01% | 1 | 0.09% |
| Andrey Vagin | 2 | 0.01% | 1 | 0.09% |
| Ladi Prosek | 2 | 0.01% | 1 | 0.09% |
| Gustavo A. R. Silva | 2 | 0.01% | 1 | 0.09% |
| Shakeel Butt | 2 | 0.01% | 1 | 0.09% |
| Christoffer Dall | 2 | 0.01% | 1 | 0.09% |
| Björn Helgaas | 2 | 0.01% | 1 | 0.09% |
| Linus Torvalds (pre-git) | 2 | 0.01% | 1 | 0.09% |
| Yao Yuan | 1 | 0.00% | 1 | 0.09% |
| Linus Torvalds | 1 | 0.00% | 1 | 0.09% |
| Weidong Han | 1 | 0.00% | 1 | 0.09% |
| Isaku Yamahata | 1 | 0.00% | 1 | 0.09% |
| Mauro Carvalho Chehab | 1 | 0.00% | 1 | 0.09% |
| Ackerley Tng | 1 | 0.00% | 1 | 0.09% |
| KarimAllah Ahmed | 1 | 0.00% | 1 | 0.09% |
| Liang Chen | 1 | 0.00% | 1 | 0.09% |
| Tiejun Chen | 1 | 0.00% | 1 | 0.09% |
| Breno Leitão | 1 | 0.00% | 1 | 0.09% |
| Al Viro | 1 | 0.00% | 1 | 0.09% |
| Kunwu Chan | 1 | 0.00% | 1 | 0.09% |
| Wei Liu | 1 | 0.00% | 1 | 0.09% |
| Total | 29596 | 1119 |
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// SPDX-License-Identifier: GPL-2.0-only /* * Kernel-based Virtual Machine driver for Linux * * This module enables machines with Intel VT-x extensions to run virtual * machines without emulation or binary translation. * * MMU support * * Copyright (C) 2006 Qumranet, Inc. * Copyright 2010 Red Hat, Inc. and/or its affiliates. * * Authors: * Yaniv Kamay <yaniv@qumranet.com> * Avi Kivity <avi@qumranet.com> */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include "irq.h" #include "ioapic.h" #include "mmu.h" #include "mmu_internal.h" #include "tdp_mmu.h" #include "x86.h" #include "kvm_cache_regs.h" #include "smm.h" #include "kvm_emulate.h" #include "page_track.h" #include "cpuid.h" #include "spte.h" #include <linux/kvm_host.h> #include <linux/types.h> #include <linux/string.h> #include <linux/mm.h> #include <linux/highmem.h> #include <linux/moduleparam.h> #include <linux/export.h> #include <linux/swap.h> #include <linux/hugetlb.h> #include <linux/compiler.h> #include <linux/srcu.h> #include <linux/slab.h> #include <linux/sched/signal.h> #include <linux/uaccess.h> #include <linux/hash.h> #include <linux/kern_levels.h> #include <linux/kstrtox.h> #include <linux/kthread.h> #include <linux/wordpart.h> #include <asm/page.h> #include <asm/memtype.h> #include <asm/cmpxchg.h> #include <asm/io.h> #include <asm/set_memory.h> #include <asm/spec-ctrl.h> #include <asm/vmx.h> #include "trace.h" static bool nx_hugepage_mitigation_hard_disabled; int __read_mostly nx_huge_pages = -1; static uint __read_mostly nx_huge_pages_recovery_period_ms; #ifdef CONFIG_PREEMPT_RT /* Recovery can cause latency spikes, disable it for PREEMPT_RT. */ static uint __read_mostly nx_huge_pages_recovery_ratio = 0; #else static uint __read_mostly nx_huge_pages_recovery_ratio = 60; #endif static int get_nx_huge_pages(char *buffer, const struct kernel_param *kp); static int set_nx_huge_pages(const char *val, const struct kernel_param *kp); static int set_nx_huge_pages_recovery_param(const char *val, const struct kernel_param *kp); static const struct kernel_param_ops nx_huge_pages_ops = { .set = set_nx_huge_pages, .get = get_nx_huge_pages, }; static const struct kernel_param_ops nx_huge_pages_recovery_param_ops = { .set = set_nx_huge_pages_recovery_param, .get = param_get_uint, }; module_param_cb(nx_huge_pages, &nx_huge_pages_ops, &nx_huge_pages, 0644); __MODULE_PARM_TYPE(nx_huge_pages, "bool"); module_param_cb(nx_huge_pages_recovery_ratio, &nx_huge_pages_recovery_param_ops, &nx_huge_pages_recovery_ratio, 0644); __MODULE_PARM_TYPE(nx_huge_pages_recovery_ratio, "uint"); module_param_cb(nx_huge_pages_recovery_period_ms, &nx_huge_pages_recovery_param_ops, &nx_huge_pages_recovery_period_ms, 0644); __MODULE_PARM_TYPE(nx_huge_pages_recovery_period_ms, "uint"); static bool __read_mostly force_flush_and_sync_on_reuse; module_param_named(flush_on_reuse, force_flush_and_sync_on_reuse, bool, 0644); /* * When setting this variable to true it enables Two-Dimensional-Paging * where the hardware walks 2 page tables: * 1. the guest-virtual to guest-physical * 2. while doing 1. it walks guest-physical to host-physical * If the hardware supports that we don't need to do shadow paging. */ bool tdp_enabled = false; static bool __ro_after_init tdp_mmu_allowed; #ifdef CONFIG_X86_64 bool __read_mostly tdp_mmu_enabled = true; module_param_named(tdp_mmu, tdp_mmu_enabled, bool, 0444); #endif static int max_huge_page_level __read_mostly; static int tdp_root_level __read_mostly; static int max_tdp_level __read_mostly; #define PTE_PREFETCH_NUM 8 #include <trace/events/kvm.h> /* make pte_list_desc fit well in cache lines */ #define PTE_LIST_EXT 14 /* * struct pte_list_desc is the core data structure used to implement a custom * list for tracking a set of related SPTEs, e.g. all the SPTEs that map a * given GFN when used in the context of rmaps. Using a custom list allows KVM * to optimize for the common case where many GFNs will have at most a handful * of SPTEs pointing at them, i.e. allows packing multiple SPTEs into a small * memory footprint, which in turn improves runtime performance by exploiting * cache locality. * * A list is comprised of one or more pte_list_desc objects (descriptors). * Each individual descriptor stores up to PTE_LIST_EXT SPTEs. If a descriptor * is full and a new SPTEs needs to be added, a new descriptor is allocated and * becomes the head of the list. This means that by definitions, all tail * descriptors are full. * * Note, the meta data fields are deliberately placed at the start of the * structure to optimize the cacheline layout; accessing the descriptor will * touch only a single cacheline so long as @spte_count<=6 (or if only the * descriptors metadata is accessed). */ struct pte_list_desc { struct pte_list_desc *more; /* The number of PTEs stored in _this_ descriptor. */ u32 spte_count; /* The number of PTEs stored in all tails of this descriptor. */ u32 tail_count; u64 *sptes[PTE_LIST_EXT]; }; struct kvm_shadow_walk_iterator { u64 addr; hpa_t shadow_addr; u64 *sptep; int level; unsigned index; }; #define for_each_shadow_entry_using_root(_vcpu, _root, _addr, _walker) \ for (shadow_walk_init_using_root(&(_walker), (_vcpu), \ (_root), (_addr)); \ shadow_walk_okay(&(_walker)); \ shadow_walk_next(&(_walker))) #define for_each_shadow_entry(_vcpu, _addr, _walker) \ for (shadow_walk_init(&(_walker), _vcpu, _addr); \ shadow_walk_okay(&(_walker)); \ shadow_walk_next(&(_walker))) #define for_each_shadow_entry_lockless(_vcpu, _addr, _walker, spte) \ for (shadow_walk_init(&(_walker), _vcpu, _addr); \ shadow_walk_okay(&(_walker)) && \ ({ spte = mmu_spte_get_lockless(_walker.sptep); 1; }); \ __shadow_walk_next(&(_walker), spte)) static struct kmem_cache *pte_list_desc_cache; struct kmem_cache *mmu_page_header_cache; static void mmu_spte_set(u64 *sptep, u64 spte); struct kvm_mmu_role_regs { const unsigned long cr0; const unsigned long cr4; const u64 efer; }; #define CREATE_TRACE_POINTS #include "mmutrace.h" /* * Yes, lot's of underscores. They're a hint that you probably shouldn't be * reading from the role_regs. Once the root_role is constructed, it becomes * the single source of truth for the MMU's state. */ #define BUILD_MMU_ROLE_REGS_ACCESSOR(reg, name, flag) \ static inline bool __maybe_unused \ ____is_##reg##_##name(const struct kvm_mmu_role_regs *regs) \ { \ return !!(regs->reg & flag); \ } BUILD_MMU_ROLE_REGS_ACCESSOR(cr0, pg, X86_CR0_PG); BUILD_MMU_ROLE_REGS_ACCESSOR(cr0, wp, X86_CR0_WP); BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, pse, X86_CR4_PSE); BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, pae, X86_CR4_PAE); BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, smep, X86_CR4_SMEP); BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, smap, X86_CR4_SMAP); BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, pke, X86_CR4_PKE); BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, la57, X86_CR4_LA57); BUILD_MMU_ROLE_REGS_ACCESSOR(efer, nx, EFER_NX); BUILD_MMU_ROLE_REGS_ACCESSOR(efer, lma, EFER_LMA); /* * The MMU itself (with a valid role) is the single source of truth for the * MMU. Do not use the regs used to build the MMU/role, nor the vCPU. The * regs don't account for dependencies, e.g. clearing CR4 bits if CR0.PG=1, * and the vCPU may be incorrect/irrelevant. */ #define BUILD_MMU_ROLE_ACCESSOR(base_or_ext, reg, name) \ static inline bool __maybe_unused is_##reg##_##name(struct kvm_mmu *mmu) \ { \ return !!(mmu->cpu_role. base_or_ext . reg##_##name); \ } BUILD_MMU_ROLE_ACCESSOR(base, cr0, wp); BUILD_MMU_ROLE_ACCESSOR(ext, cr4, pse); BUILD_MMU_ROLE_ACCESSOR(ext, cr4, smep); BUILD_MMU_ROLE_ACCESSOR(ext, cr4, smap); BUILD_MMU_ROLE_ACCESSOR(ext, cr4, pke); BUILD_MMU_ROLE_ACCESSOR(ext, cr4, la57); BUILD_MMU_ROLE_ACCESSOR(base, efer, nx); BUILD_MMU_ROLE_ACCESSOR(ext, efer, lma); static inline bool is_cr0_pg(struct kvm_mmu *mmu) { return mmu->cpu_role.base.level > 0; } static inline bool is_cr4_pae(struct kvm_mmu *mmu) { return !mmu->cpu_role.base.has_4_byte_gpte; } static struct kvm_mmu_role_regs vcpu_to_role_regs(struct kvm_vcpu *vcpu) { struct kvm_mmu_role_regs regs = { .cr0 = kvm_read_cr0_bits(vcpu, KVM_MMU_CR0_ROLE_BITS), .cr4 = kvm_read_cr4_bits(vcpu, KVM_MMU_CR4_ROLE_BITS), .efer = vcpu->arch.efer, }; return regs; } static unsigned long get_guest_cr3(struct kvm_vcpu *vcpu) { return kvm_read_cr3(vcpu); } static inline unsigned long kvm_mmu_get_guest_pgd(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu) { if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && mmu->get_guest_pgd == get_guest_cr3) return kvm_read_cr3(vcpu); return mmu->get_guest_pgd(vcpu); } static inline bool kvm_available_flush_remote_tlbs_range(void) { #if IS_ENABLED(CONFIG_HYPERV) return kvm_x86_ops.flush_remote_tlbs_range; #else return false; #endif } static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index); /* Flush the range of guest memory mapped by the given SPTE. */ static void kvm_flush_remote_tlbs_sptep(struct kvm *kvm, u64 *sptep) { struct kvm_mmu_page *sp = sptep_to_sp(sptep); gfn_t gfn = kvm_mmu_page_get_gfn(sp, spte_index(sptep)); kvm_flush_remote_tlbs_gfn(kvm, gfn, sp->role.level); } static void mark_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, u64 gfn, unsigned int access) { u64 spte = make_mmio_spte(vcpu, gfn, access); trace_mark_mmio_spte(sptep, gfn, spte); mmu_spte_set(sptep, spte); } static gfn_t get_mmio_spte_gfn(u64 spte) { u64 gpa = spte & shadow_nonpresent_or_rsvd_lower_gfn_mask; gpa |= (spte >> SHADOW_NONPRESENT_OR_RSVD_MASK_LEN) & shadow_nonpresent_or_rsvd_mask; return gpa >> PAGE_SHIFT; } static unsigned get_mmio_spte_access(u64 spte) { return spte & shadow_mmio_access_mask; } static bool check_mmio_spte(struct kvm_vcpu *vcpu, u64 spte) { u64 kvm_gen, spte_gen, gen; gen = kvm_vcpu_memslots(vcpu)->generation; if (unlikely(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS)) return false; kvm_gen = gen & MMIO_SPTE_GEN_MASK; spte_gen = get_mmio_spte_generation(spte); trace_check_mmio_spte(spte, kvm_gen, spte_gen); return likely(kvm_gen == spte_gen); } static int is_cpuid_PSE36(void) { return 1; } #ifdef CONFIG_X86_64 static void __set_spte(u64 *sptep, u64 spte) { KVM_MMU_WARN_ON(is_ept_ve_possible(spte)); WRITE_ONCE(*sptep, spte); } static void __update_clear_spte_fast(u64 *sptep, u64 spte) { KVM_MMU_WARN_ON(is_ept_ve_possible(spte)); WRITE_ONCE(*sptep, spte); } static u64 __update_clear_spte_slow(u64 *sptep, u64 spte) { KVM_MMU_WARN_ON(is_ept_ve_possible(spte)); return xchg(sptep, spte); } static u64 __get_spte_lockless(u64 *sptep) { return READ_ONCE(*sptep); } #else union split_spte { struct { u32 spte_low; u32 spte_high; }; u64 spte; }; static void count_spte_clear(u64 *sptep, u64 spte) { struct kvm_mmu_page *sp = sptep_to_sp(sptep); if (is_shadow_present_pte(spte)) return; /* Ensure the spte is completely set before we increase the count */ smp_wmb(); sp->clear_spte_count++; } static void __set_spte(u64 *sptep, u64 spte) { union split_spte *ssptep, sspte; ssptep = (union split_spte *)sptep; sspte = (union split_spte)spte; ssptep->spte_high = sspte.spte_high; /* * If we map the spte from nonpresent to present, We should store * the high bits firstly, then set present bit, so cpu can not * fetch this spte while we are setting the spte. */ smp_wmb(); WRITE_ONCE(ssptep->spte_low, sspte.spte_low); } static void __update_clear_spte_fast(u64 *sptep, u64 spte) { union split_spte *ssptep, sspte; ssptep = (union split_spte *)sptep; sspte = (union split_spte)spte; WRITE_ONCE(ssptep->spte_low, sspte.spte_low); /* * If we map the spte from present to nonpresent, we should clear * present bit firstly to avoid vcpu fetch the old high bits. */ smp_wmb(); ssptep->spte_high = sspte.spte_high; count_spte_clear(sptep, spte); } static u64 __update_clear_spte_slow(u64 *sptep, u64 spte) { union split_spte *ssptep, sspte, orig; ssptep = (union split_spte *)sptep; sspte = (union split_spte)spte; /* xchg acts as a barrier before the setting of the high bits */ orig.spte_low = xchg(&ssptep->spte_low, sspte.spte_low); orig.spte_high = ssptep->spte_high; ssptep->spte_high = sspte.spte_high; count_spte_clear(sptep, spte); return orig.spte; } /* * The idea using the light way get the spte on x86_32 guest is from * gup_get_pte (mm/gup.c). * * An spte tlb flush may be pending, because they are coalesced and * we are running out of the MMU lock. Therefore * we need to protect against in-progress updates of the spte. * * Reading the spte while an update is in progress may get the old value * for the high part of the spte. The race is fine for a present->non-present * change (because the high part of the spte is ignored for non-present spte), * but for a present->present change we must reread the spte. * * All such changes are done in two steps (present->non-present and * non-present->present), hence it is enough to count the number of * present->non-present updates: if it changed while reading the spte, * we might have hit the race. This is done using clear_spte_count. */ static u64 __get_spte_lockless(u64 *sptep) { struct kvm_mmu_page *sp = sptep_to_sp(sptep); union split_spte spte, *orig = (union split_spte *)sptep; int count; retry: count = sp->clear_spte_count; smp_rmb(); spte.spte_low = orig->spte_low; smp_rmb(); spte.spte_high = orig->spte_high; smp_rmb(); if (unlikely(spte.spte_low != orig->spte_low || count != sp->clear_spte_count)) goto retry; return spte.spte; } #endif /* Rules for using mmu_spte_set: * Set the sptep from nonpresent to present. * Note: the sptep being assigned *must* be either not present * or in a state where the hardware will not attempt to update * the spte. */ static void mmu_spte_set(u64 *sptep, u64 new_spte) { WARN_ON_ONCE(is_shadow_present_pte(*sptep)); __set_spte(sptep, new_spte); } /* Rules for using mmu_spte_update: * Update the state bits, it means the mapped pfn is not changed. * * Returns true if the TLB needs to be flushed */ static bool mmu_spte_update(u64 *sptep, u64 new_spte) { u64 old_spte = *sptep; WARN_ON_ONCE(!is_shadow_present_pte(new_spte)); check_spte_writable_invariants(new_spte); if (!is_shadow_present_pte(old_spte)) { mmu_spte_set(sptep, new_spte); return false; } if (!spte_has_volatile_bits(old_spte)) __update_clear_spte_fast(sptep, new_spte); else old_spte = __update_clear_spte_slow(sptep, new_spte); WARN_ON_ONCE(!is_shadow_present_pte(old_spte) || spte_to_pfn(old_spte) != spte_to_pfn(new_spte)); return leaf_spte_change_needs_tlb_flush(old_spte, new_spte); } /* * Rules for using mmu_spte_clear_track_bits: * It sets the sptep from present to nonpresent, and track the * state bits, it is used to clear the last level sptep. * Returns the old PTE. */ static u64 mmu_spte_clear_track_bits(struct kvm *kvm, u64 *sptep) { u64 old_spte = *sptep; int level = sptep_to_sp(sptep)->role.level; if (!is_shadow_present_pte(old_spte) || !spte_has_volatile_bits(old_spte)) __update_clear_spte_fast(sptep, SHADOW_NONPRESENT_VALUE); else old_spte = __update_clear_spte_slow(sptep, SHADOW_NONPRESENT_VALUE); if (!is_shadow_present_pte(old_spte)) return old_spte; kvm_update_page_stats(kvm, level, -1); return old_spte; } /* * Rules for using mmu_spte_clear_no_track: * Directly clear spte without caring the state bits of sptep, * it is used to set the upper level spte. */ static void mmu_spte_clear_no_track(u64 *sptep) { __update_clear_spte_fast(sptep, SHADOW_NONPRESENT_VALUE); } static u64 mmu_spte_get_lockless(u64 *sptep) { return __get_spte_lockless(sptep); } static inline bool is_tdp_mmu_active(struct kvm_vcpu *vcpu) { return tdp_mmu_enabled && vcpu->arch.mmu->root_role.direct; } static void walk_shadow_page_lockless_begin(struct kvm_vcpu *vcpu) { if (is_tdp_mmu_active(vcpu)) { kvm_tdp_mmu_walk_lockless_begin(); } else { /* * Prevent page table teardown by making any free-er wait during * kvm_flush_remote_tlbs() IPI to all active vcpus. */ local_irq_disable(); /* * Make sure a following spte read is not reordered ahead of the write * to vcpu->mode. */ smp_store_mb(vcpu->mode, READING_SHADOW_PAGE_TABLES); } } static void walk_shadow_page_lockless_end(struct kvm_vcpu *vcpu) { if (is_tdp_mmu_active(vcpu)) { kvm_tdp_mmu_walk_lockless_end(); } else { /* * Make sure the write to vcpu->mode is not reordered in front of * reads to sptes. If it does, kvm_mmu_commit_zap_page() can see us * OUTSIDE_GUEST_MODE and proceed to free the shadow page table. */ smp_store_release(&vcpu->mode, OUTSIDE_GUEST_MODE); local_irq_enable(); } } static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu, bool maybe_indirect) { int r; /* 1 rmap, 1 parent PTE per level, and the prefetched rmaps. */ r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache, 1 + PT64_ROOT_MAX_LEVEL + PTE_PREFETCH_NUM); if (r) return r; r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_shadow_page_cache, PT64_ROOT_MAX_LEVEL); if (r) return r; if (maybe_indirect) { r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_shadowed_info_cache, PT64_ROOT_MAX_LEVEL); if (r) return r; } return kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache, PT64_ROOT_MAX_LEVEL); } static void mmu_free_memory_caches(struct kvm_vcpu *vcpu) { kvm_mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache); kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadow_page_cache); kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadowed_info_cache); kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache); } static void mmu_free_pte_list_desc(struct pte_list_desc *pte_list_desc) { kmem_cache_free(pte_list_desc_cache, pte_list_desc); } static bool sp_has_gptes(struct kvm_mmu_page *sp); static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index) { if (sp->role.passthrough) return sp->gfn; if (sp->shadowed_translation) return sp->shadowed_translation[index] >> PAGE_SHIFT; return sp->gfn + (index << ((sp->role.level - 1) * SPTE_LEVEL_BITS)); } /* * For leaf SPTEs, fetch the *guest* access permissions being shadowed. Note * that the SPTE itself may have a more constrained access permissions that * what the guest enforces. For example, a guest may create an executable * huge PTE but KVM may disallow execution to mitigate iTLB multihit. */ static u32 kvm_mmu_page_get_access(struct kvm_mmu_page *sp, int index) { if (sp->shadowed_translation) return sp->shadowed_translation[index] & ACC_ALL; /* * For direct MMUs (e.g. TDP or non-paging guests) or passthrough SPs, * KVM is not shadowing any guest page tables, so the "guest access * permissions" are just ACC_ALL. * * For direct SPs in indirect MMUs (shadow paging), i.e. when KVM * is shadowing a guest huge page with small pages, the guest access * permissions being shadowed are the access permissions of the huge * page. * * In both cases, sp->role.access contains the correct access bits. */ return sp->role.access; } static void kvm_mmu_page_set_translation(struct kvm_mmu_page *sp, int index, gfn_t gfn, unsigned int access) { if (sp->shadowed_translation) { sp->shadowed_translation[index] = (gfn << PAGE_SHIFT) | access; return; } WARN_ONCE(access != kvm_mmu_page_get_access(sp, index), "access mismatch under %s page %llx (expected %u, got %u)\n", sp->role.passthrough ? "passthrough" : "direct", sp->gfn, kvm_mmu_page_get_access(sp, index), access); WARN_ONCE(gfn != kvm_mmu_page_get_gfn(sp, index), "gfn mismatch under %s page %llx (expected %llx, got %llx)\n", sp->role.passthrough ? "passthrough" : "direct", sp->gfn, kvm_mmu_page_get_gfn(sp, index), gfn); } static void kvm_mmu_page_set_access(struct kvm_mmu_page *sp, int index, unsigned int access) { gfn_t gfn = kvm_mmu_page_get_gfn(sp, index); kvm_mmu_page_set_translation(sp, index, gfn, access); } /* * Return the pointer to the large page information for a given gfn, * handling slots that are not large page aligned. */ static struct kvm_lpage_info *lpage_info_slot(gfn_t gfn, const struct kvm_memory_slot *slot, int level) { unsigned long idx; idx = gfn_to_index(gfn, slot->base_gfn, level); return &slot->arch.lpage_info[level - 2][idx]; } /* * The most significant bit in disallow_lpage tracks whether or not memory * attributes are mixed, i.e. not identical for all gfns at the current level. * The lower order bits are used to refcount other cases where a hugepage is * disallowed, e.g. if KVM has shadow a page table at the gfn. */ #define KVM_LPAGE_MIXED_FLAG BIT(31) static void update_gfn_disallow_lpage_count(const struct kvm_memory_slot *slot, gfn_t gfn, int count) { struct kvm_lpage_info *linfo; int old, i; for (i = PG_LEVEL_2M; i <= KVM_MAX_HUGEPAGE_LEVEL; ++i) { linfo = lpage_info_slot(gfn, slot, i); old = linfo->disallow_lpage; linfo->disallow_lpage += count; WARN_ON_ONCE((old ^ linfo->disallow_lpage) & KVM_LPAGE_MIXED_FLAG); } } void kvm_mmu_gfn_disallow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn) { update_gfn_disallow_lpage_count(slot, gfn, 1); } void kvm_mmu_gfn_allow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn) { update_gfn_disallow_lpage_count(slot, gfn, -1); } static void account_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp) { struct kvm_memslots *slots; struct kvm_memory_slot *slot; gfn_t gfn; kvm->arch.indirect_shadow_pages++; /* * Ensure indirect_shadow_pages is elevated prior to re-reading guest * child PTEs in FNAME(gpte_changed), i.e. guarantee either in-flight * emulated writes are visible before re-reading guest PTEs, or that * an emulated write will see the elevated count and acquire mmu_lock * to update SPTEs. Pairs with the smp_mb() in kvm_mmu_track_write(). */ smp_mb(); gfn = sp->gfn; slots = kvm_memslots_for_spte_role(kvm, sp->role); slot = __gfn_to_memslot(slots, gfn); /* the non-leaf shadow pages are keeping readonly. */ if (sp->role.level > PG_LEVEL_4K) return __kvm_write_track_add_gfn(kvm, slot, gfn); kvm_mmu_gfn_disallow_lpage(slot, gfn); if (kvm_mmu_slot_gfn_write_protect(kvm, slot, gfn, PG_LEVEL_4K)) kvm_flush_remote_tlbs_gfn(kvm, gfn, PG_LEVEL_4K); } void track_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp) { /* * If it's possible to replace the shadow page with an NX huge page, * i.e. if the shadow page is the only thing currently preventing KVM * from using a huge page, add the shadow page to the list of "to be * zapped for NX recovery" pages. Note, the shadow page can already be * on the list if KVM is reusing an existing shadow page, i.e. if KVM * links a shadow page at multiple points. */ if (!list_empty(&sp->possible_nx_huge_page_link)) return; ++kvm->stat.nx_lpage_splits; list_add_tail(&sp->possible_nx_huge_page_link, &kvm->arch.possible_nx_huge_pages); } static void account_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp, bool nx_huge_page_possible) { sp->nx_huge_page_disallowed = true; if (nx_huge_page_possible) track_possible_nx_huge_page(kvm, sp); } static void unaccount_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp) { struct kvm_memslots *slots; struct kvm_memory_slot *slot; gfn_t gfn; kvm->arch.indirect_shadow_pages--; gfn = sp->gfn; slots = kvm_memslots_for_spte_role(kvm, sp->role); slot = __gfn_to_memslot(slots, gfn); if (sp->role.level > PG_LEVEL_4K) return __kvm_write_track_remove_gfn(kvm, slot, gfn); kvm_mmu_gfn_allow_lpage(slot, gfn); } void untrack_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp) { if (list_empty(&sp->possible_nx_huge_page_link)) return; --kvm->stat.nx_lpage_splits; list_del_init(&sp->possible_nx_huge_page_link); } static void unaccount_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp) { sp->nx_huge_page_disallowed = false; untrack_possible_nx_huge_page(kvm, sp); } static struct kvm_memory_slot *gfn_to_memslot_dirty_bitmap(struct kvm_vcpu *vcpu, gfn_t gfn, bool no_dirty_log) { struct kvm_memory_slot *slot; slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn); if (!slot || slot->flags & KVM_MEMSLOT_INVALID) return NULL; if (no_dirty_log && kvm_slot_dirty_track_enabled(slot)) return NULL; return slot; } /* * About rmap_head encoding: * * If the bit zero of rmap_head->val is clear, then it points to the only spte * in this rmap chain. Otherwise, (rmap_head->val & ~1) points to a struct * pte_list_desc containing more mappings. */ #define KVM_RMAP_MANY BIT(0) /* * Returns the number of pointers in the rmap chain, not counting the new one. */ static int pte_list_add(struct kvm_mmu_memory_cache *cache, u64 *spte, struct kvm_rmap_head *rmap_head) { struct pte_list_desc *desc; int count = 0; if (!rmap_head->val) { rmap_head->val = (unsigned long)spte; } else if (!(rmap_head->val & KVM_RMAP_MANY)) { desc = kvm_mmu_memory_cache_alloc(cache); desc->sptes[0] = (u64 *)rmap_head->val; desc->sptes[1] = spte; desc->spte_count = 2; desc->tail_count = 0; rmap_head->val = (unsigned long)desc | KVM_RMAP_MANY; ++count; } else { desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); count = desc->tail_count + desc->spte_count; /* * If the previous head is full, allocate a new head descriptor * as tail descriptors are always kept full. */ if (desc->spte_count == PTE_LIST_EXT) { desc = kvm_mmu_memory_cache_alloc(cache); desc->more = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); desc->spte_count = 0; desc->tail_count = count; rmap_head->val = (unsigned long)desc | KVM_RMAP_MANY; } desc->sptes[desc->spte_count++] = spte; } return count; } static void pte_list_desc_remove_entry(struct kvm *kvm, struct kvm_rmap_head *rmap_head, struct pte_list_desc *desc, int i) { struct pte_list_desc *head_desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); int j = head_desc->spte_count - 1; /* * The head descriptor should never be empty. A new head is added only * when adding an entry and the previous head is full, and heads are * removed (this flow) when they become empty. */ KVM_BUG_ON_DATA_CORRUPTION(j < 0, kvm); /* * Replace the to-be-freed SPTE with the last valid entry from the head * descriptor to ensure that tail descriptors are full at all times. * Note, this also means that tail_count is stable for each descriptor. */ desc->sptes[i] = head_desc->sptes[j]; head_desc->sptes[j] = NULL; head_desc->spte_count--; if (head_desc->spte_count) return; /* * The head descriptor is empty. If there are no tail descriptors, * nullify the rmap head to mark the list as empty, else point the rmap * head at the next descriptor, i.e. the new head. */ if (!head_desc->more) rmap_head->val = 0; else rmap_head->val = (unsigned long)head_desc->more | KVM_RMAP_MANY; mmu_free_pte_list_desc(head_desc); } static void pte_list_remove(struct kvm *kvm, u64 *spte, struct kvm_rmap_head *rmap_head) { struct pte_list_desc *desc; int i; if (KVM_BUG_ON_DATA_CORRUPTION(!rmap_head->val, kvm)) return; if (!(rmap_head->val & KVM_RMAP_MANY)) { if (KVM_BUG_ON_DATA_CORRUPTION((u64 *)rmap_head->val != spte, kvm)) return; rmap_head->val = 0; } else { desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); while (desc) { for (i = 0; i < desc->spte_count; ++i) { if (desc->sptes[i] == spte) { pte_list_desc_remove_entry(kvm, rmap_head, desc, i); return; } } desc = desc->more; } KVM_BUG_ON_DATA_CORRUPTION(true, kvm); } } static void kvm_zap_one_rmap_spte(struct kvm *kvm, struct kvm_rmap_head *rmap_head, u64 *sptep) { mmu_spte_clear_track_bits(kvm, sptep); pte_list_remove(kvm, sptep, rmap_head); } /* Return true if at least one SPTE was zapped, false otherwise */ static bool kvm_zap_all_rmap_sptes(struct kvm *kvm, struct kvm_rmap_head *rmap_head) { struct pte_list_desc *desc, *next; int i; if (!rmap_head->val) return false; if (!(rmap_head->val & KVM_RMAP_MANY)) { mmu_spte_clear_track_bits(kvm, (u64 *)rmap_head->val); goto out; } desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); for (; desc; desc = next) { for (i = 0; i < desc->spte_count; i++) mmu_spte_clear_track_bits(kvm, desc->sptes[i]); next = desc->more; mmu_free_pte_list_desc(desc); } out: /* rmap_head is meaningless now, remember to reset it */ rmap_head->val = 0; return true; } unsigned int pte_list_count(struct kvm_rmap_head *rmap_head) { struct pte_list_desc *desc; if (!rmap_head->val) return 0; else if (!(rmap_head->val & KVM_RMAP_MANY)) return 1; desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); return desc->tail_count + desc->spte_count; } static struct kvm_rmap_head *gfn_to_rmap(gfn_t gfn, int level, const struct kvm_memory_slot *slot) { unsigned long idx; idx = gfn_to_index(gfn, slot->base_gfn, level); return &slot->arch.rmap[level - PG_LEVEL_4K][idx]; } static void rmap_remove(struct kvm *kvm, u64 *spte) { struct kvm_memslots *slots; struct kvm_memory_slot *slot; struct kvm_mmu_page *sp; gfn_t gfn; struct kvm_rmap_head *rmap_head; sp = sptep_to_sp(spte); gfn = kvm_mmu_page_get_gfn(sp, spte_index(spte)); /* * Unlike rmap_add, rmap_remove does not run in the context of a vCPU * so we have to determine which memslots to use based on context * information in sp->role. */ slots = kvm_memslots_for_spte_role(kvm, sp->role); slot = __gfn_to_memslot(slots, gfn); rmap_head = gfn_to_rmap(gfn, sp->role.level, slot); pte_list_remove(kvm, spte, rmap_head); } /* * Used by the following functions to iterate through the sptes linked by a * rmap. All fields are private and not assumed to be used outside. */ struct rmap_iterator { /* private fields */ struct pte_list_desc *desc; /* holds the sptep if not NULL */ int pos; /* index of the sptep */ }; /* * Iteration must be started by this function. This should also be used after * removing/dropping sptes from the rmap link because in such cases the * information in the iterator may not be valid. * * Returns sptep if found, NULL otherwise. */ static u64 *rmap_get_first(struct kvm_rmap_head *rmap_head, struct rmap_iterator *iter) { u64 *sptep; if (!rmap_head->val) return NULL; if (!(rmap_head->val & KVM_RMAP_MANY)) { iter->desc = NULL; sptep = (u64 *)rmap_head->val; goto out; } iter->desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); iter->pos = 0; sptep = iter->desc->sptes[iter->pos]; out: BUG_ON(!is_shadow_present_pte(*sptep)); return sptep; } /* * Must be used with a valid iterator: e.g. after rmap_get_first(). * * Returns sptep if found, NULL otherwise. */ static u64 *rmap_get_next(struct rmap_iterator *iter) { u64 *sptep; if (iter->desc) { if (iter->pos < PTE_LIST_EXT - 1) { ++iter->pos; sptep = iter->desc->sptes[iter->pos]; if (sptep) goto out; } iter->desc = iter->desc->more; if (iter->desc) { iter->pos = 0; /* desc->sptes[0] cannot be NULL */ sptep = iter->desc->sptes[iter->pos]; goto out; } } return NULL; out: BUG_ON(!is_shadow_present_pte(*sptep)); return sptep; } #define for_each_rmap_spte(_rmap_head_, _iter_, _spte_) \ for (_spte_ = rmap_get_first(_rmap_head_, _iter_); \ _spte_; _spte_ = rmap_get_next(_iter_)) static void drop_spte(struct kvm *kvm, u64 *sptep) { u64 old_spte = mmu_spte_clear_track_bits(kvm, sptep); if (is_shadow_present_pte(old_spte)) rmap_remove(kvm, sptep); } static void drop_large_spte(struct kvm *kvm, u64 *sptep, bool flush) { struct kvm_mmu_page *sp; sp = sptep_to_sp(sptep); WARN_ON_ONCE(sp->role.level == PG_LEVEL_4K); drop_spte(kvm, sptep); if (flush) kvm_flush_remote_tlbs_sptep(kvm, sptep); } /* * Write-protect on the specified @sptep, @pt_protect indicates whether * spte write-protection is caused by protecting shadow page table. * * Note: write protection is difference between dirty logging and spte * protection: * - for dirty logging, the spte can be set to writable at anytime if * its dirty bitmap is properly set. * - for spte protection, the spte can be writable only after unsync-ing * shadow page. * * Return true if tlb need be flushed. */ static bool spte_write_protect(u64 *sptep, bool pt_protect) { u64 spte = *sptep; if (!is_writable_pte(spte) && !(pt_protect && is_mmu_writable_spte(spte))) return false; if (pt_protect) spte &= ~shadow_mmu_writable_mask; spte = spte & ~PT_WRITABLE_MASK; return mmu_spte_update(sptep, spte); } static bool rmap_write_protect(struct kvm_rmap_head *rmap_head, bool pt_protect) { u64 *sptep; struct rmap_iterator iter; bool flush = false; for_each_rmap_spte(rmap_head, &iter, sptep) flush |= spte_write_protect(sptep, pt_protect); return flush; } static bool spte_clear_dirty(u64 *sptep) { u64 spte = *sptep; KVM_MMU_WARN_ON(!spte_ad_enabled(spte)); spte &= ~shadow_dirty_mask; return mmu_spte_update(sptep, spte); } /* * Gets the GFN ready for another round of dirty logging by clearing the * - D bit on ad-enabled SPTEs, and * - W bit on ad-disabled SPTEs. * Returns true iff any D or W bits were cleared. */ static bool __rmap_clear_dirty(struct kvm *kvm, struct kvm_rmap_head *rmap_head, const struct kvm_memory_slot *slot) { u64 *sptep; struct rmap_iterator iter; bool flush = false; for_each_rmap_spte(rmap_head, &iter, sptep) if (spte_ad_need_write_protect(*sptep)) flush |= test_and_clear_bit(PT_WRITABLE_SHIFT, (unsigned long *)sptep); else flush |= spte_clear_dirty(sptep); return flush; } static void kvm_mmu_write_protect_pt_masked(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn_offset, unsigned long mask) { struct kvm_rmap_head *rmap_head; if (tdp_mmu_enabled) kvm_tdp_mmu_clear_dirty_pt_masked(kvm, slot, slot->base_gfn + gfn_offset, mask, true); if (!kvm_memslots_have_rmaps(kvm)) return; while (mask) { rmap_head = gfn_to_rmap(slot->base_gfn + gfn_offset + __ffs(mask), PG_LEVEL_4K, slot); rmap_write_protect(rmap_head, false); /* clear the first set bit */ mask &= mask - 1; } } static void kvm_mmu_clear_dirty_pt_masked(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn_offset, unsigned long mask) { struct kvm_rmap_head *rmap_head; if (tdp_mmu_enabled) kvm_tdp_mmu_clear_dirty_pt_masked(kvm, slot, slot->base_gfn + gfn_offset, mask, false); if (!kvm_memslots_have_rmaps(kvm)) return; while (mask) { rmap_head = gfn_to_rmap(slot->base_gfn + gfn_offset + __ffs(mask), PG_LEVEL_4K, slot); __rmap_clear_dirty(kvm, rmap_head, slot); /* clear the first set bit */ mask &= mask - 1; } } void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn_offset, unsigned long mask) { /* * If the slot was assumed to be "initially all dirty", write-protect * huge pages to ensure they are split to 4KiB on the first write (KVM * dirty logs at 4KiB granularity). If eager page splitting is enabled, * immediately try to split huge pages, e.g. so that vCPUs don't get * saddled with the cost of splitting. * * The gfn_offset is guaranteed to be aligned to 64, but the base_gfn * of memslot has no such restriction, so the range can cross two large * pages. */ if (kvm_dirty_log_manual_protect_and_init_set(kvm)) { gfn_t start = slot->base_gfn + gfn_offset + __ffs(mask); gfn_t end = slot->base_gfn + gfn_offset + __fls(mask); if (READ_ONCE(eager_page_split)) kvm_mmu_try_split_huge_pages(kvm, slot, start, end + 1, PG_LEVEL_4K); kvm_mmu_slot_gfn_write_protect(kvm, slot, start, PG_LEVEL_2M); /* Cross two large pages? */ if (ALIGN(start << PAGE_SHIFT, PMD_SIZE) != ALIGN(end << PAGE_SHIFT, PMD_SIZE)) kvm_mmu_slot_gfn_write_protect(kvm, slot, end, PG_LEVEL_2M); } /* * (Re)Enable dirty logging for all 4KiB SPTEs that map the GFNs in * mask. If PML is enabled and the GFN doesn't need to be write- * protected for other reasons, e.g. shadow paging, clear the Dirty bit. * Otherwise clear the Writable bit. * * Note that kvm_mmu_clear_dirty_pt_masked() is called whenever PML is * enabled but it chooses between clearing the Dirty bit and Writeable * bit based on the context. */ if (kvm_x86_ops.cpu_dirty_log_size) kvm_mmu_clear_dirty_pt_masked(kvm, slot, gfn_offset, mask); else kvm_mmu_write_protect_pt_masked(kvm, slot, gfn_offset, mask); } int kvm_cpu_dirty_log_size(void) { return kvm_x86_ops.cpu_dirty_log_size; } bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm, struct kvm_memory_slot *slot, u64 gfn, int min_level) { struct kvm_rmap_head *rmap_head; int i; bool write_protected = false; if (kvm_memslots_have_rmaps(kvm)) { for (i = min_level; i <= KVM_MAX_HUGEPAGE_LEVEL; ++i) { rmap_head = gfn_to_rmap(gfn, i, slot); write_protected |= rmap_write_protect(rmap_head, true); } } if (tdp_mmu_enabled) write_protected |= kvm_tdp_mmu_write_protect_gfn(kvm, slot, gfn, min_level); return write_protected; } static bool kvm_vcpu_write_protect_gfn(struct kvm_vcpu *vcpu, u64 gfn) { struct kvm_memory_slot *slot; slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn); return kvm_mmu_slot_gfn_write_protect(vcpu->kvm, slot, gfn, PG_LEVEL_4K); } static bool kvm_zap_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head, const struct kvm_memory_slot *slot) { return kvm_zap_all_rmap_sptes(kvm, rmap_head); } struct slot_rmap_walk_iterator { /* input fields. */ const struct kvm_memory_slot *slot; gfn_t start_gfn; gfn_t end_gfn; int start_level; int end_level; /* output fields. */ gfn_t gfn; struct kvm_rmap_head *rmap; int level; /* private field. */ struct kvm_rmap_head *end_rmap; }; static void rmap_walk_init_level(struct slot_rmap_walk_iterator *iterator, int level) { iterator->level = level; iterator->gfn = iterator->start_gfn; iterator->rmap = gfn_to_rmap(iterator->gfn, level, iterator->slot); iterator->end_rmap = gfn_to_rmap(iterator->end_gfn, level, iterator->slot); } static void slot_rmap_walk_init(struct slot_rmap_walk_iterator *iterator, const struct kvm_memory_slot *slot, int start_level, int end_level, gfn_t start_gfn, gfn_t end_gfn) { iterator->slot = slot; iterator->start_level = start_level; iterator->end_level = end_level; iterator->start_gfn = start_gfn; iterator->end_gfn = end_gfn; rmap_walk_init_level(iterator, iterator->start_level); } static bool slot_rmap_walk_okay(struct slot_rmap_walk_iterator *iterator) { return !!iterator->rmap; } static void slot_rmap_walk_next(struct slot_rmap_walk_iterator *iterator) { while (++iterator->rmap <= iterator->end_rmap) { iterator->gfn += KVM_PAGES_PER_HPAGE(iterator->level); if (iterator->rmap->val) return; } if (++iterator->level > iterator->end_level) { iterator->rmap = NULL; return; } rmap_walk_init_level(iterator, iterator->level); } #define for_each_slot_rmap_range(_slot_, _start_level_, _end_level_, \ _start_gfn, _end_gfn, _iter_) \ for (slot_rmap_walk_init(_iter_, _slot_, _start_level_, \ _end_level_, _start_gfn, _end_gfn); \ slot_rmap_walk_okay(_iter_); \ slot_rmap_walk_next(_iter_)) /* The return value indicates if tlb flush on all vcpus is needed. */ typedef bool (*slot_rmaps_handler) (struct kvm *kvm, struct kvm_rmap_head *rmap_head, const struct kvm_memory_slot *slot); static __always_inline bool __walk_slot_rmaps(struct kvm *kvm, const struct kvm_memory_slot *slot, slot_rmaps_handler fn, int start_level, int end_level, gfn_t start_gfn, gfn_t end_gfn, bool can_yield, bool flush_on_yield, bool flush) { struct slot_rmap_walk_iterator iterator; lockdep_assert_held_write(&kvm->mmu_lock); for_each_slot_rmap_range(slot, start_level, end_level, start_gfn, end_gfn, &iterator) { if (iterator.rmap) flush |= fn(kvm, iterator.rmap, slot); if (!can_yield) continue; if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) { if (flush && flush_on_yield) { kvm_flush_remote_tlbs_range(kvm, start_gfn, iterator.gfn - start_gfn + 1); flush = false; } cond_resched_rwlock_write(&kvm->mmu_lock); } } return flush; } static __always_inline bool walk_slot_rmaps(struct kvm *kvm, const struct kvm_memory_slot *slot, slot_rmaps_handler fn, int start_level, int end_level, bool flush_on_yield) { return __walk_slot_rmaps(kvm, slot, fn, start_level, end_level, slot->base_gfn, slot->base_gfn + slot->npages - 1, true, flush_on_yield, false); } static __always_inline bool walk_slot_rmaps_4k(struct kvm *kvm, const struct kvm_memory_slot *slot, slot_rmaps_handler fn, bool flush_on_yield) { return walk_slot_rmaps(kvm, slot, fn, PG_LEVEL_4K, PG_LEVEL_4K, flush_on_yield); } static bool __kvm_rmap_zap_gfn_range(struct kvm *kvm, const struct kvm_memory_slot *slot, gfn_t start, gfn_t end, bool can_yield, bool flush) { return __walk_slot_rmaps(kvm, slot, kvm_zap_rmap, PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL, start, end - 1, can_yield, true, flush); } bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range) { bool flush = false; /* * To prevent races with vCPUs faulting in a gfn using stale data, * zapping a gfn range must be protected by mmu_invalidate_in_progress * (and mmu_invalidate_seq). The only exception is memslot deletion; * in that case, SRCU synchronization ensures that SPTEs are zapped * after all vCPUs have unlocked SRCU, guaranteeing that vCPUs see the * invalid slot. */ lockdep_assert_once(kvm->mmu_invalidate_in_progress || lockdep_is_held(&kvm->slots_lock)); if (kvm_memslots_have_rmaps(kvm)) flush = __kvm_rmap_zap_gfn_range(kvm, range->slot, range->start, range->end, range->may_block, flush); if (tdp_mmu_enabled) flush = kvm_tdp_mmu_unmap_gfn_range(kvm, range, flush); if (kvm_x86_ops.set_apic_access_page_addr && range->slot->id == APIC_ACCESS_PAGE_PRIVATE_MEMSLOT) kvm_make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD); return flush; } #define RMAP_RECYCLE_THRESHOLD 1000 static void __rmap_add(struct kvm *kvm, struct kvm_mmu_memory_cache *cache, const struct kvm_memory_slot *slot, u64 *spte, gfn_t gfn, unsigned int access) { struct kvm_mmu_page *sp; struct kvm_rmap_head *rmap_head; int rmap_count; sp = sptep_to_sp(spte); kvm_mmu_page_set_translation(sp, spte_index(spte), gfn, access); kvm_update_page_stats(kvm, sp->role.level, 1); rmap_head = gfn_to_rmap(gfn, sp->role.level, slot); rmap_count = pte_list_add(cache, spte, rmap_head); if (rmap_count > kvm->stat.max_mmu_rmap_size) kvm->stat.max_mmu_rmap_size = rmap_count; if (rmap_count > RMAP_RECYCLE_THRESHOLD) { kvm_zap_all_rmap_sptes(kvm, rmap_head); kvm_flush_remote_tlbs_gfn(kvm, gfn, sp->role.level); } } static void rmap_add(struct kvm_vcpu *vcpu, const struct kvm_memory_slot *slot, u64 *spte, gfn_t gfn, unsigned int access) { struct kvm_mmu_memory_cache *cache = &vcpu->arch.mmu_pte_list_desc_cache; __rmap_add(vcpu->kvm, cache, slot, spte, gfn, access); } static bool kvm_rmap_age_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range, bool test_only) { struct slot_rmap_walk_iterator iterator; struct rmap_iterator iter; bool young = false; u64 *sptep; for_each_slot_rmap_range(range->slot, PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL, range->start, range->end - 1, &iterator) { for_each_rmap_spte(iterator.rmap, &iter, sptep) { u64 spte = *sptep; if (!is_accessed_spte(spte)) continue; if (test_only) return true; if (spte_ad_enabled(spte)) { clear_bit((ffs(shadow_accessed_mask) - 1), (unsigned long *)sptep); } else { /* * WARN if mmu_spte_update() signals the need * for a TLB flush, as Access tracking a SPTE * should never trigger an _immediate_ flush. */ spte = mark_spte_for_access_track(spte); WARN_ON_ONCE(mmu_spte_update(sptep, spte)); } young = true; } } return young; } bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { bool young = false; if (kvm_memslots_have_rmaps(kvm)) young = kvm_rmap_age_gfn_range(kvm, range, false); if (tdp_mmu_enabled) young |= kvm_tdp_mmu_age_gfn_range(kvm, range); return young; } bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { bool young = false; if (kvm_memslots_have_rmaps(kvm)) young = kvm_rmap_age_gfn_range(kvm, range, true); if (tdp_mmu_enabled) young |= kvm_tdp_mmu_test_age_gfn(kvm, range); return young; } static void kvm_mmu_check_sptes_at_free(struct kvm_mmu_page *sp) { #ifdef CONFIG_KVM_PROVE_MMU int i; for (i = 0; i < SPTE_ENT_PER_PAGE; i++) { if (KVM_MMU_WARN_ON(is_shadow_present_pte(sp->spt[i]))) pr_err_ratelimited("SPTE %llx (@ %p) for gfn %llx shadow-present at free", sp->spt[i], &sp->spt[i], kvm_mmu_page_get_gfn(sp, i)); } #endif } static void kvm_account_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp) { kvm->arch.n_used_mmu_pages++; kvm_account_pgtable_pages((void *)sp->spt, +1); } static void kvm_unaccount_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp) { kvm->arch.n_used_mmu_pages--; kvm_account_pgtable_pages((void *)sp->spt, -1); } static void kvm_mmu_free_shadow_page(struct kvm_mmu_page *sp) { kvm_mmu_check_sptes_at_free(sp); hlist_del(&sp->hash_link); list_del(&sp->link); free_page((unsigned long)sp->spt); free_page((unsigned long)sp->shadowed_translation); kmem_cache_free(mmu_page_header_cache, sp); } static unsigned kvm_page_table_hashfn(gfn_t gfn) { return hash_64(gfn, KVM_MMU_HASH_SHIFT); } static void mmu_page_add_parent_pte(struct kvm_mmu_memory_cache *cache, struct kvm_mmu_page *sp, u64 *parent_pte) { if (!parent_pte) return; pte_list_add(cache, parent_pte, &sp->parent_ptes); } static void mmu_page_remove_parent_pte(struct kvm *kvm, struct kvm_mmu_page *sp, u64 *parent_pte) { pte_list_remove(kvm, parent_pte, &sp->parent_ptes); } static void drop_parent_pte(struct kvm *kvm, struct kvm_mmu_page *sp, u64 *parent_pte) { mmu_page_remove_parent_pte(kvm, sp, parent_pte); mmu_spte_clear_no_track(parent_pte); } static void mark_unsync(u64 *spte); static void kvm_mmu_mark_parents_unsync(struct kvm_mmu_page *sp) { u64 *sptep; struct rmap_iterator iter; for_each_rmap_spte(&sp->parent_ptes, &iter, sptep) { mark_unsync(sptep); } } static void mark_unsync(u64 *spte) { struct kvm_mmu_page *sp; sp = sptep_to_sp(spte); if (__test_and_set_bit(spte_index(spte), sp->unsync_child_bitmap)) return; if (sp->unsync_children++) return; kvm_mmu_mark_parents_unsync(sp); } #define KVM_PAGE_ARRAY_NR 16 struct kvm_mmu_pages { struct mmu_page_and_offset { struct kvm_mmu_page *sp; unsigned int idx; } page[KVM_PAGE_ARRAY_NR]; unsigned int nr; }; static int mmu_pages_add(struct kvm_mmu_pages *pvec, struct kvm_mmu_page *sp, int idx) { int i; if (sp->unsync) for (i=0; i < pvec->nr; i++) if (pvec->page[i].sp == sp) return 0; pvec->page[pvec->nr].sp = sp; pvec->page[pvec->nr].idx = idx; pvec->nr++; return (pvec->nr == KVM_PAGE_ARRAY_NR); } static inline void clear_unsync_child_bit(struct kvm_mmu_page *sp, int idx) { --sp->unsync_children; WARN_ON_ONCE((int)sp->unsync_children < 0); __clear_bit(idx, sp->unsync_child_bitmap); } static int __mmu_unsync_walk(struct kvm_mmu_page *sp, struct kvm_mmu_pages *pvec) { int i, ret, nr_unsync_leaf = 0; for_each_set_bit(i, sp->unsync_child_bitmap, 512) { struct kvm_mmu_page *child; u64 ent = sp->spt[i]; if (!is_shadow_present_pte(ent) || is_large_pte(ent)) { clear_unsync_child_bit(sp, i); continue; } child = spte_to_child_sp(ent); if (child->unsync_children) { if (mmu_pages_add(pvec, child, i)) return -ENOSPC; ret = __mmu_unsync_walk(child, pvec); if (!ret) { clear_unsync_child_bit(sp, i); continue; } else if (ret > 0) { nr_unsync_leaf += ret; } else return ret; } else if (child->unsync) { nr_unsync_leaf++; if (mmu_pages_add(pvec, child, i)) return -ENOSPC; } else clear_unsync_child_bit(sp, i); } return nr_unsync_leaf; } #define INVALID_INDEX (-1) static int mmu_unsync_walk(struct kvm_mmu_page *sp, struct kvm_mmu_pages *pvec) { pvec->nr = 0; if (!sp->unsync_children) return 0; mmu_pages_add(pvec, sp, INVALID_INDEX); return __mmu_unsync_walk(sp, pvec); } static void kvm_unlink_unsync_page(struct kvm *kvm, struct kvm_mmu_page *sp) { WARN_ON_ONCE(!sp->unsync); trace_kvm_mmu_sync_page(sp); sp->unsync = 0; --kvm->stat.mmu_unsync; } static bool kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp, struct list_head *invalid_list); static void kvm_mmu_commit_zap_page(struct kvm *kvm, struct list_head *invalid_list); static bool sp_has_gptes(struct kvm_mmu_page *sp) { if (sp->role.direct) return false; if (sp->role.passthrough) return false; return true; } #define for_each_valid_sp(_kvm, _sp, _list) \ hlist_for_each_entry(_sp, _list, hash_link) \ if (is_obsolete_sp((_kvm), (_sp))) { \ } else #define for_each_gfn_valid_sp_with_gptes(_kvm, _sp, _gfn) \ for_each_valid_sp(_kvm, _sp, \ &(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)]) \ if ((_sp)->gfn != (_gfn) || !sp_has_gptes(_sp)) {} else static bool kvm_sync_page_check(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) { union kvm_mmu_page_role root_role = vcpu->arch.mmu->root_role; /* * Ignore various flags when verifying that it's safe to sync a shadow * page using the current MMU context. * * - level: not part of the overall MMU role and will never match as the MMU's * level tracks the root level * - access: updated based on the new guest PTE * - quadrant: not part of the overall MMU role (similar to level) */ const union kvm_mmu_page_role sync_role_ign = { .level = 0xf, .access = 0x7, .quadrant = 0x3, .passthrough = 0x1, }; /* * Direct pages can never be unsync, and KVM should never attempt to * sync a shadow page for a different MMU context, e.g. if the role * differs then the memslot lookup (SMM vs. non-SMM) will be bogus, the * reserved bits checks will be wrong, etc... */ if (WARN_ON_ONCE(sp->role.direct || !vcpu->arch.mmu->sync_spte || (sp->role.word ^ root_role.word) & ~sync_role_ign.word)) return false; return true; } static int kvm_sync_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int i) { /* sp->spt[i] has initial value of shadow page table allocation */ if (sp->spt[i] == SHADOW_NONPRESENT_VALUE) return 0; return vcpu->arch.mmu->sync_spte(vcpu, sp, i); } static int __kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) { int flush = 0; int i; if (!kvm_sync_page_check(vcpu, sp)) return -1; for (i = 0; i < SPTE_ENT_PER_PAGE; i++) { int ret = kvm_sync_spte(vcpu, sp, i); if (ret < -1) return -1; flush |= ret; } /* * Note, any flush is purely for KVM's correctness, e.g. when dropping * an existing SPTE or clearing W/A/D bits to ensure an mmu_notifier * unmap or dirty logging event doesn't fail to flush. The guest is * responsible for flushing the TLB to ensure any changes in protection * bits are recognized, i.e. until the guest flushes or page faults on * a relevant address, KVM is architecturally allowed to let vCPUs use * cached translations with the old protection bits. */ return flush; } static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, struct list_head *invalid_list) { int ret = __kvm_sync_page(vcpu, sp); if (ret < 0) kvm_mmu_prepare_zap_page(vcpu->kvm, sp, invalid_list); return ret; } static bool kvm_mmu_remote_flush_or_zap(struct kvm *kvm, struct list_head *invalid_list, bool remote_flush) { if (!remote_flush && list_empty(invalid_list)) return false; if (!list_empty(invalid_list)) kvm_mmu_commit_zap_page(kvm, invalid_list); else kvm_flush_remote_tlbs(kvm); return true; } static bool is_obsolete_sp(struct kvm *kvm, struct kvm_mmu_page *sp) { if (sp->role.invalid) return true; /* TDP MMU pages do not use the MMU generation. */ return !is_tdp_mmu_page(sp) && unlikely(sp->mmu_valid_gen != kvm->arch.mmu_valid_gen); } struct mmu_page_path { struct kvm_mmu_page *parent[PT64_ROOT_MAX_LEVEL]; unsigned int idx[PT64_ROOT_MAX_LEVEL]; }; #define for_each_sp(pvec, sp, parents, i) \ for (i = mmu_pages_first(&pvec, &parents); \ i < pvec.nr && ({ sp = pvec.page[i].sp; 1;}); \ i = mmu_pages_next(&pvec, &parents, i)) static int mmu_pages_next(struct kvm_mmu_pages *pvec, struct mmu_page_path *parents, int i) { int n; for (n = i+1; n < pvec->nr; n++) { struct kvm_mmu_page *sp = pvec->page[n].sp; unsigned idx = pvec->page[n].idx; int level = sp->role.level; parents->idx[level-1] = idx; if (level == PG_LEVEL_4K) break; parents->parent[level-2] = sp; } return n; } static int mmu_pages_first(struct kvm_mmu_pages *pvec, struct mmu_page_path *parents) { struct kvm_mmu_page *sp; int level; if (pvec->nr == 0) return 0; WARN_ON_ONCE(pvec->page[0].idx != INVALID_INDEX); sp = pvec->page[0].sp; level = sp->role.level; WARN_ON_ONCE(level == PG_LEVEL_4K); parents->parent[level-2] = sp; /* Also set up a sentinel. Further entries in pvec are all * children of sp, so this element is never overwritten. */ parents->parent[level-1] = NULL; return mmu_pages_next(pvec, parents, 0); } static void mmu_pages_clear_parents(struct mmu_page_path *parents) { struct kvm_mmu_page *sp; unsigned int level = 0; do { unsigned int idx = parents->idx[level]; sp = parents->parent[level]; if (!sp) return; WARN_ON_ONCE(idx == INVALID_INDEX); clear_unsync_child_bit(sp, idx); level++; } while (!sp->unsync_children); } static int mmu_sync_children(struct kvm_vcpu *vcpu, struct kvm_mmu_page *parent, bool can_yield) { int i; struct kvm_mmu_page *sp; struct mmu_page_path parents; struct kvm_mmu_pages pages; LIST_HEAD(invalid_list); bool flush = false; while (mmu_unsync_walk(parent, &pages)) { bool protected = false; for_each_sp(pages, sp, parents, i) protected |= kvm_vcpu_write_protect_gfn(vcpu, sp->gfn); if (protected) { kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, true); flush = false; } for_each_sp(pages, sp, parents, i) { kvm_unlink_unsync_page(vcpu->kvm, sp); flush |= kvm_sync_page(vcpu, sp, &invalid_list) > 0; mmu_pages_clear_parents(&parents); } if (need_resched() || rwlock_needbreak(&vcpu->kvm->mmu_lock)) { kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, flush); if (!can_yield) { kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); return -EINTR; } cond_resched_rwlock_write(&vcpu->kvm->mmu_lock); flush = false; } } kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, flush); return 0; } static void __clear_sp_write_flooding_count(struct kvm_mmu_page *sp) { atomic_set(&sp->write_flooding_count, 0); } static void clear_sp_write_flooding_count(u64 *spte) { __clear_sp_write_flooding_count(sptep_to_sp(spte)); } /* * The vCPU is required when finding indirect shadow pages; the shadow * page may already exist and syncing it needs the vCPU pointer in * order to read guest page tables. Direct shadow pages are never * unsync, thus @vcpu can be NULL if @role.direct is true. */ static struct kvm_mmu_page *kvm_mmu_find_shadow_page(struct kvm *kvm, struct kvm_vcpu *vcpu, gfn_t gfn, struct hlist_head *sp_list, union kvm_mmu_page_role role) { struct kvm_mmu_page *sp; int ret; int collisions = 0; LIST_HEAD(invalid_list); for_each_valid_sp(kvm, sp, sp_list) { if (sp->gfn != gfn) { collisions++; continue; } if (sp->role.word != role.word) { /* * If the guest is creating an upper-level page, zap * unsync pages for the same gfn. While it's possible * the guest is using recursive page tables, in all * likelihood the guest has stopped using the unsync * page and is installing a completely unrelated page. * Unsync pages must not be left as is, because the new * upper-level page will be write-protected. */ if (role.level > PG_LEVEL_4K && sp->unsync) kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list); continue; } /* unsync and write-flooding only apply to indirect SPs. */ if (sp->role.direct) goto out; if (sp->unsync) { if (KVM_BUG_ON(!vcpu, kvm)) break; /* * The page is good, but is stale. kvm_sync_page does * get the latest guest state, but (unlike mmu_unsync_children) * it doesn't write-protect the page or mark it synchronized! * This way the validity of the mapping is ensured, but the * overhead of write protection is not incurred until the * guest invalidates the TLB mapping. This allows multiple * SPs for a single gfn to be unsync. * * If the sync fails, the page is zapped. If so, break * in order to rebuild it. */ ret = kvm_sync_page(vcpu, sp, &invalid_list); if (ret < 0) break; WARN_ON_ONCE(!list_empty(&invalid_list)); if (ret > 0) kvm_flush_remote_tlbs(kvm); } __clear_sp_write_flooding_count(sp); goto out; } sp = NULL; ++kvm->stat.mmu_cache_miss; out: kvm_mmu_commit_zap_page(kvm, &invalid_list); if (collisions > kvm->stat.max_mmu_page_hash_collisions) kvm->stat.max_mmu_page_hash_collisions = collisions; return sp; } /* Caches used when allocating a new shadow page. */ struct shadow_page_caches { struct kvm_mmu_memory_cache *page_header_cache; struct kvm_mmu_memory_cache *shadow_page_cache; struct kvm_mmu_memory_cache *shadowed_info_cache; }; static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm *kvm, struct shadow_page_caches *caches, gfn_t gfn, struct hlist_head *sp_list, union kvm_mmu_page_role role) { struct kvm_mmu_page *sp; sp = kvm_mmu_memory_cache_alloc(caches->page_header_cache); sp->spt = kvm_mmu_memory_cache_alloc(caches->shadow_page_cache); if (!role.direct && role.level <= KVM_MAX_HUGEPAGE_LEVEL) sp->shadowed_translation = kvm_mmu_memory_cache_alloc(caches->shadowed_info_cache); set_page_private(virt_to_page(sp->spt), (unsigned long)sp); INIT_LIST_HEAD(&sp->possible_nx_huge_page_link); /* * active_mmu_pages must be a FIFO list, as kvm_zap_obsolete_pages() * depends on valid pages being added to the head of the list. See * comments in kvm_zap_obsolete_pages(). */ sp->mmu_valid_gen = kvm->arch.mmu_valid_gen; list_add(&sp->link, &kvm->arch.active_mmu_pages); kvm_account_mmu_page(kvm, sp); sp->gfn = gfn; sp->role = role; hlist_add_head(&sp->hash_link, sp_list); if (sp_has_gptes(sp)) account_shadowed(kvm, sp); return sp; } /* Note, @vcpu may be NULL if @role.direct is true; see kvm_mmu_find_shadow_page. */ static struct kvm_mmu_page *__kvm_mmu_get_shadow_page(struct kvm *kvm, struct kvm_vcpu *vcpu, struct shadow_page_caches *caches, gfn_t gfn, union kvm_mmu_page_role role) { struct hlist_head *sp_list; struct kvm_mmu_page *sp; bool created = false; sp_list = &kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)]; sp = kvm_mmu_find_shadow_page(kvm, vcpu, gfn, sp_list, role); if (!sp) { created = true; sp = kvm_mmu_alloc_shadow_page(kvm, caches, gfn, sp_list, role); } trace_kvm_mmu_get_page(sp, created); return sp; } static struct kvm_mmu_page *kvm_mmu_get_shadow_page(struct kvm_vcpu *vcpu, gfn_t gfn, union kvm_mmu_page_role role) { struct shadow_page_caches caches = { .page_header_cache = &vcpu->arch.mmu_page_header_cache, .shadow_page_cache = &vcpu->arch.mmu_shadow_page_cache, .shadowed_info_cache = &vcpu->arch.mmu_shadowed_info_cache, }; return __kvm_mmu_get_shadow_page(vcpu->kvm, vcpu, &caches, gfn, role); } static union kvm_mmu_page_role kvm_mmu_child_role(u64 *sptep, bool direct, unsigned int access) { struct kvm_mmu_page *parent_sp = sptep_to_sp(sptep); union kvm_mmu_page_role role; role = parent_sp->role; role.level--; role.access = access; role.direct = direct; role.passthrough = 0; /* * If the guest has 4-byte PTEs then that means it's using 32-bit, * 2-level, non-PAE paging. KVM shadows such guests with PAE paging * (i.e. 8-byte PTEs). The difference in PTE size means that KVM must * shadow each guest page table with multiple shadow page tables, which * requires extra bookkeeping in the role. * * Specifically, to shadow the guest's page directory (which covers a * 4GiB address space), KVM uses 4 PAE page directories, each mapping * 1GiB of the address space. @role.quadrant encodes which quarter of * the address space each maps. * * To shadow the guest's page tables (which each map a 4MiB region), KVM * uses 2 PAE page tables, each mapping a 2MiB region. For these, * @role.quadrant encodes which half of the region they map. * * Concretely, a 4-byte PDE consumes bits 31:22, while an 8-byte PDE * consumes bits 29:21. To consume bits 31:30, KVM's uses 4 shadow * PDPTEs; those 4 PAE page directories are pre-allocated and their * quadrant is assigned in mmu_alloc_root(). A 4-byte PTE consumes * bits 21:12, while an 8-byte PTE consumes bits 20:12. To consume * bit 21 in the PTE (the child here), KVM propagates that bit to the * quadrant, i.e. sets quadrant to '0' or '1'. The parent 8-byte PDE * covers bit 21 (see above), thus the quadrant is calculated from the * _least_ significant bit of the PDE index. */ if (role.has_4_byte_gpte) { WARN_ON_ONCE(role.level != PG_LEVEL_4K); role.quadrant = spte_index(sptep) & 1; } return role; } static struct kvm_mmu_page *kvm_mmu_get_child_sp(struct kvm_vcpu *vcpu, u64 *sptep, gfn_t gfn, bool direct, unsigned int access) { union kvm_mmu_page_role role; if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) return ERR_PTR(-EEXIST); role = kvm_mmu_child_role(sptep, direct, access); return kvm_mmu_get_shadow_page(vcpu, gfn, role); } static void shadow_walk_init_using_root(struct kvm_shadow_walk_iterator *iterator, struct kvm_vcpu *vcpu, hpa_t root, u64 addr) { iterator->addr = addr; iterator->shadow_addr = root; iterator->level = vcpu->arch.mmu->root_role.level; if (iterator->level >= PT64_ROOT_4LEVEL && vcpu->arch.mmu->cpu_role.base.level < PT64_ROOT_4LEVEL && !vcpu->arch.mmu->root_role.direct) iterator->level = PT32E_ROOT_LEVEL; if (iterator->level == PT32E_ROOT_LEVEL) { /* * prev_root is currently only used for 64-bit hosts. So only * the active root_hpa is valid here. */ BUG_ON(root != vcpu->arch.mmu->root.hpa); iterator->shadow_addr = vcpu->arch.mmu->pae_root[(addr >> 30) & 3]; iterator->shadow_addr &= SPTE_BASE_ADDR_MASK; --iterator->level; if (!iterator->shadow_addr) iterator->level = 0; } } static void shadow_walk_init(struct kvm_shadow_walk_iterator *iterator, struct kvm_vcpu *vcpu, u64 addr) { shadow_walk_init_using_root(iterator, vcpu, vcpu->arch.mmu->root.hpa, addr); } static bool shadow_walk_okay(struct kvm_shadow_walk_iterator *iterator) { if (iterator->level < PG_LEVEL_4K) return false; iterator->index = SPTE_INDEX(iterator->addr, iterator->level); iterator->sptep = ((u64 *)__va(iterator->shadow_addr)) + iterator->index; return true; } static void __shadow_walk_next(struct kvm_shadow_walk_iterator *iterator, u64 spte) { if (!is_shadow_present_pte(spte) || is_last_spte(spte, iterator->level)) { iterator->level = 0; return; } iterator->shadow_addr = spte & SPTE_BASE_ADDR_MASK; --iterator->level; } static void shadow_walk_next(struct kvm_shadow_walk_iterator *iterator) { __shadow_walk_next(iterator, *iterator->sptep); } static void __link_shadow_page(struct kvm *kvm, struct kvm_mmu_memory_cache *cache, u64 *sptep, struct kvm_mmu_page *sp, bool flush) { u64 spte; BUILD_BUG_ON(VMX_EPT_WRITABLE_MASK != PT_WRITABLE_MASK); /* * If an SPTE is present already, it must be a leaf and therefore * a large one. Drop it, and flush the TLB if needed, before * installing sp. */ if (is_shadow_present_pte(*sptep)) drop_large_spte(kvm, sptep, flush); spte = make_nonleaf_spte(sp->spt, sp_ad_disabled(sp)); mmu_spte_set(sptep, spte); mmu_page_add_parent_pte(cache, sp, sptep); /* * The non-direct sub-pagetable must be updated before linking. For * L1 sp, the pagetable is updated via kvm_sync_page() in * kvm_mmu_find_shadow_page() without write-protecting the gfn, * so sp->unsync can be true or false. For higher level non-direct * sp, the pagetable is updated/synced via mmu_sync_children() in * FNAME(fetch)(), so sp->unsync_children can only be false. * WARN_ON_ONCE() if anything happens unexpectedly. */ if (WARN_ON_ONCE(sp->unsync_children) || sp->unsync) mark_unsync(sptep); } static void link_shadow_page(struct kvm_vcpu *vcpu, u64 *sptep, struct kvm_mmu_page *sp) { __link_shadow_page(vcpu->kvm, &vcpu->arch.mmu_pte_list_desc_cache, sptep, sp, true); } static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned direct_access) { if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) { struct kvm_mmu_page *child; /* * For the direct sp, if the guest pte's dirty bit * changed form clean to dirty, it will corrupt the * sp's access: allow writable in the read-only sp, * so we should update the spte at this point to get * a new sp with the correct access. */ child = spte_to_child_sp(*sptep); if (child->role.access == direct_access) return; drop_parent_pte(vcpu->kvm, child, sptep); kvm_flush_remote_tlbs_sptep(vcpu->kvm, sptep); } } /* Returns the number of zapped non-leaf child shadow pages. */ static int mmu_page_zap_pte(struct kvm *kvm, struct kvm_mmu_page *sp, u64 *spte, struct list_head *invalid_list) { u64 pte; struct kvm_mmu_page *child; pte = *spte; if (is_shadow_present_pte(pte)) { if (is_last_spte(pte, sp->role.level)) { drop_spte(kvm, spte); } else { child = spte_to_child_sp(pte); drop_parent_pte(kvm, child, spte); /* * Recursively zap nested TDP SPs, parentless SPs are * unlikely to be used again in the near future. This * avoids retaining a large number of stale nested SPs. */ if (tdp_enabled && invalid_list && child->role.guest_mode && !child->parent_ptes.val) return kvm_mmu_prepare_zap_page(kvm, child, invalid_list); } } else if (is_mmio_spte(kvm, pte)) { mmu_spte_clear_no_track(spte); } return 0; } static int kvm_mmu_page_unlink_children(struct kvm *kvm, struct kvm_mmu_page *sp, struct list_head *invalid_list) { int zapped = 0; unsigned i; for (i = 0; i < SPTE_ENT_PER_PAGE; ++i) zapped += mmu_page_zap_pte(kvm, sp, sp->spt + i, invalid_list); return zapped; } static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp) { u64 *sptep; struct rmap_iterator iter; while ((sptep = rmap_get_first(&sp->parent_ptes, &iter))) drop_parent_pte(kvm, sp, sptep); } static int mmu_zap_unsync_children(struct kvm *kvm, struct kvm_mmu_page *parent, struct list_head *invalid_list) { int i, zapped = 0; struct mmu_page_path parents; struct kvm_mmu_pages pages; if (parent->role.level == PG_LEVEL_4K) return 0; while (mmu_unsync_walk(parent, &pages)) { struct kvm_mmu_page *sp; for_each_sp(pages, sp, parents, i) { kvm_mmu_prepare_zap_page(kvm, sp, invalid_list); mmu_pages_clear_parents(&parents); zapped++; } } return zapped; } static bool __kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp, struct list_head *invalid_list, int *nr_zapped) { bool list_unstable, zapped_root = false; lockdep_assert_held_write(&kvm->mmu_lock); trace_kvm_mmu_prepare_zap_page(sp); ++kvm->stat.mmu_shadow_zapped; *nr_zapped = mmu_zap_unsync_children(kvm, sp, invalid_list); *nr_zapped += kvm_mmu_page_unlink_children(kvm, sp, invalid_list); kvm_mmu_unlink_parents(kvm, sp); /* Zapping children means active_mmu_pages has become unstable. */ list_unstable = *nr_zapped; if (!sp->role.invalid && sp_has_gptes(sp)) unaccount_shadowed(kvm, sp); if (sp->unsync) kvm_unlink_unsync_page(kvm, sp); if (!sp->root_count) { /* Count self */ (*nr_zapped)++; /* * Already invalid pages (previously active roots) are not on * the active page list. See list_del() in the "else" case of * !sp->root_count. */ if (sp->role.invalid) list_add(&sp->link, invalid_list); else list_move(&sp->link, invalid_list); kvm_unaccount_mmu_page(kvm, sp); } else { /* * Remove the active root from the active page list, the root * will be explicitly freed when the root_count hits zero. */ list_del(&sp->link); /* * Obsolete pages cannot be used on any vCPUs, see the comment * in kvm_mmu_zap_all_fast(). Note, is_obsolete_sp() also * treats invalid shadow pages as being obsolete. */ zapped_root = !is_obsolete_sp(kvm, sp); } if (sp->nx_huge_page_disallowed) unaccount_nx_huge_page(kvm, sp); sp->role.invalid = 1; /* * Make the request to free obsolete roots after marking the root * invalid, otherwise other vCPUs may not see it as invalid. */ if (zapped_root) kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_FREE_OBSOLETE_ROOTS); return list_unstable; } static bool kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp, struct list_head *invalid_list) { int nr_zapped; __kvm_mmu_prepare_zap_page(kvm, sp, invalid_list, &nr_zapped); return nr_zapped; } static void kvm_mmu_commit_zap_page(struct kvm *kvm, struct list_head *invalid_list) { struct kvm_mmu_page *sp, *nsp; if (list_empty(invalid_list)) return; /* * We need to make sure everyone sees our modifications to * the page tables and see changes to vcpu->mode here. The barrier * in the kvm_flush_remote_tlbs() achieves this. This pairs * with vcpu_enter_guest and walk_shadow_page_lockless_begin/end. * * In addition, kvm_flush_remote_tlbs waits for all vcpus to exit * guest mode and/or lockless shadow page table walks. */ kvm_flush_remote_tlbs(kvm); list_for_each_entry_safe(sp, nsp, invalid_list, link) { WARN_ON_ONCE(!sp->role.invalid || sp->root_count); kvm_mmu_free_shadow_page(sp); } } static unsigned long kvm_mmu_zap_oldest_mmu_pages(struct kvm *kvm, unsigned long nr_to_zap) { unsigned long total_zapped = 0; struct kvm_mmu_page *sp, *tmp; LIST_HEAD(invalid_list); bool unstable; int nr_zapped; if (list_empty(&kvm->arch.active_mmu_pages)) return 0; restart: list_for_each_entry_safe_reverse(sp, tmp, &kvm->arch.active_mmu_pages, link) { /* * Don't zap active root pages, the page itself can't be freed * and zapping it will just force vCPUs to realloc and reload. */ if (sp->root_count) continue; unstable = __kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list, &nr_zapped); total_zapped += nr_zapped; if (total_zapped >= nr_to_zap) break; if (unstable) goto restart; } kvm_mmu_commit_zap_page(kvm, &invalid_list); kvm->stat.mmu_recycled += total_zapped; return total_zapped; } static inline unsigned long kvm_mmu_available_pages(struct kvm *kvm) { if (kvm->arch.n_max_mmu_pages > kvm->arch.n_used_mmu_pages) return kvm->arch.n_max_mmu_pages - kvm->arch.n_used_mmu_pages; return 0; } static int make_mmu_pages_available(struct kvm_vcpu *vcpu) { unsigned long avail = kvm_mmu_available_pages(vcpu->kvm); if (likely(avail >= KVM_MIN_FREE_MMU_PAGES)) return 0; kvm_mmu_zap_oldest_mmu_pages(vcpu->kvm, KVM_REFILL_PAGES - avail); /* * Note, this check is intentionally soft, it only guarantees that one * page is available, while the caller may end up allocating as many as * four pages, e.g. for PAE roots or for 5-level paging. Temporarily * exceeding the (arbitrary by default) limit will not harm the host, * being too aggressive may unnecessarily kill the guest, and getting an * exact count is far more trouble than it's worth, especially in the * page fault paths. */ if (!kvm_mmu_available_pages(vcpu->kvm)) return -ENOSPC; return 0; } /* * Changing the number of mmu pages allocated to the vm * Note: if goal_nr_mmu_pages is too small, you will get dead lock */ void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned long goal_nr_mmu_pages) { write_lock(&kvm->mmu_lock); if (kvm->arch.n_used_mmu_pages > goal_nr_mmu_pages) { kvm_mmu_zap_oldest_mmu_pages(kvm, kvm->arch.n_used_mmu_pages - goal_nr_mmu_pages); goal_nr_mmu_pages = kvm->arch.n_used_mmu_pages; } kvm->arch.n_max_mmu_pages = goal_nr_mmu_pages; write_unlock(&kvm->mmu_lock); } bool __kvm_mmu_unprotect_gfn_and_retry(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, bool always_retry) { struct kvm *kvm = vcpu->kvm; LIST_HEAD(invalid_list); struct kvm_mmu_page *sp; gpa_t gpa = cr2_or_gpa; bool r = false; /* * Bail early if there aren't any write-protected shadow pages to avoid * unnecessarily taking mmu_lock lock, e.g. if the gfn is write-tracked * by a third party. Reading indirect_shadow_pages without holding * mmu_lock is safe, as this is purely an optimization, i.e. a false * positive is benign, and a false negative will simply result in KVM * skipping the unprotect+retry path, which is also an optimization. */ if (!READ_ONCE(kvm->arch.indirect_shadow_pages)) goto out; if (!vcpu->arch.mmu->root_role.direct) { gpa = kvm_mmu_gva_to_gpa_write(vcpu, cr2_or_gpa, NULL); if (gpa == INVALID_GPA) goto out; } write_lock(&kvm->mmu_lock); for_each_gfn_valid_sp_with_gptes(kvm, sp, gpa_to_gfn(gpa)) kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list); /* * Snapshot the result before zapping, as zapping will remove all list * entries, i.e. checking the list later would yield a false negative. */ r = !list_empty(&invalid_list); kvm_mmu_commit_zap_page(kvm, &invalid_list); write_unlock(&kvm->mmu_lock); out: if (r || always_retry) { vcpu->arch.last_retry_eip = kvm_rip_read(vcpu); vcpu->arch.last_retry_addr = cr2_or_gpa; } return r; } static void kvm_unsync_page(struct kvm *kvm, struct kvm_mmu_page *sp) { trace_kvm_mmu_unsync_page(sp); ++kvm->stat.mmu_unsync; sp->unsync = 1; kvm_mmu_mark_parents_unsync(sp); } /* * Attempt to unsync any shadow pages that can be reached by the specified gfn, * KVM is creating a writable mapping for said gfn. Returns 0 if all pages * were marked unsync (or if there is no shadow page), -EPERM if the SPTE must * be write-protected. */ int mmu_try_to_unsync_pages(struct kvm *kvm, const struct kvm_memory_slot *slot, gfn_t gfn, bool synchronizing, bool prefetch) { struct kvm_mmu_page *sp; bool locked = false; /* * Force write-protection if the page is being tracked. Note, the page * track machinery is used to write-protect upper-level shadow pages, * i.e. this guards the role.level == 4K assertion below! */ if (kvm_gfn_is_write_tracked(kvm, slot, gfn)) return -EPERM; /* * The page is not write-tracked, mark existing shadow pages unsync * unless KVM is synchronizing an unsync SP. In that case, KVM must * complete emulation of the guest TLB flush before allowing shadow * pages to become unsync (writable by the guest). */ for_each_gfn_valid_sp_with_gptes(kvm, sp, gfn) { if (synchronizing) return -EPERM; if (sp->unsync) continue; if (prefetch) return -EEXIST; /* * TDP MMU page faults require an additional spinlock as they * run with mmu_lock held for read, not write, and the unsync * logic is not thread safe. Take the spinklock regardless of * the MMU type to avoid extra conditionals/parameters, there's * no meaningful penalty if mmu_lock is held for write. */ if (!locked) { locked = true; spin_lock(&kvm->arch.mmu_unsync_pages_lock); /* * Recheck after taking the spinlock, a different vCPU * may have since marked the page unsync. A false * negative on the unprotected check above is not * possible as clearing sp->unsync _must_ hold mmu_lock * for write, i.e. unsync cannot transition from 1->0 * while this CPU holds mmu_lock for read (or write). */ if (READ_ONCE(sp->unsync)) continue; } WARN_ON_ONCE(sp->role.level != PG_LEVEL_4K); kvm_unsync_page(kvm, sp); } if (locked) spin_unlock(&kvm->arch.mmu_unsync_pages_lock); /* * We need to ensure that the marking of unsync pages is visible * before the SPTE is updated to allow writes because * kvm_mmu_sync_roots() checks the unsync flags without holding * the MMU lock and so can race with this. If the SPTE was updated * before the page had been marked as unsync-ed, something like the * following could happen: * * CPU 1 CPU 2 * --------------------------------------------------------------------- * 1.2 Host updates SPTE * to be writable * 2.1 Guest writes a GPTE for GVA X. * (GPTE being in the guest page table shadowed * by the SP from CPU 1.) * This reads SPTE during the page table walk. * Since SPTE.W is read as 1, there is no * fault. * * 2.2 Guest issues TLB flush. * That causes a VM Exit. * * 2.3 Walking of unsync pages sees sp->unsync is * false and skips the page. * * 2.4 Guest accesses GVA X. * Since the mapping in the SP was not updated, * so the old mapping for GVA X incorrectly * gets used. * 1.1 Host marks SP * as unsync * (sp->unsync = true) * * The write barrier below ensures that 1.1 happens before 1.2 and thus * the situation in 2.4 does not arise. It pairs with the read barrier * in is_unsync_root(), placed between 2.1's load of SPTE.W and 2.3. */ smp_wmb(); return 0; } static int mmu_set_spte(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot, u64 *sptep, unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn, struct kvm_page_fault *fault) { struct kvm_mmu_page *sp = sptep_to_sp(sptep); int level = sp->role.level; int was_rmapped = 0; int ret = RET_PF_FIXED; bool flush = false; bool wrprot; u64 spte; /* Prefetching always gets a writable pfn. */ bool host_writable = !fault || fault->map_writable; bool prefetch = !fault || fault->prefetch; bool write_fault = fault && fault->write; if (unlikely(is_noslot_pfn(pfn))) { vcpu->stat.pf_mmio_spte_created++; mark_mmio_spte(vcpu, sptep, gfn, pte_access); return RET_PF_EMULATE; } if (is_shadow_present_pte(*sptep)) { if (prefetch) return RET_PF_SPURIOUS; /* * If we overwrite a PTE page pointer with a 2MB PMD, unlink * the parent of the now unreachable PTE. */ if (level > PG_LEVEL_4K && !is_large_pte(*sptep)) { struct kvm_mmu_page *child; u64 pte = *sptep; child = spte_to_child_sp(pte); drop_parent_pte(vcpu->kvm, child, sptep); flush = true; } else if (pfn != spte_to_pfn(*sptep)) { drop_spte(vcpu->kvm, sptep); flush = true; } else was_rmapped = 1; } wrprot = make_spte(vcpu, sp, slot, pte_access, gfn, pfn, *sptep, prefetch, false, host_writable, &spte); if (*sptep == spte) { ret = RET_PF_SPURIOUS; } else { flush |= mmu_spte_update(sptep, spte); trace_kvm_mmu_set_spte(level, gfn, sptep); } if (wrprot && write_fault) ret = RET_PF_WRITE_PROTECTED; if (flush) kvm_flush_remote_tlbs_gfn(vcpu->kvm, gfn, level); if (!was_rmapped) { WARN_ON_ONCE(ret == RET_PF_SPURIOUS); rmap_add(vcpu, slot, sptep, gfn, pte_access); } else { /* Already rmapped but the pte_access bits may have changed. */ kvm_mmu_page_set_access(sp, spte_index(sptep), pte_access); } return ret; } static bool kvm_mmu_prefetch_sptes(struct kvm_vcpu *vcpu, gfn_t gfn, u64 *sptep, int nr_pages, unsigned int access) { struct page *pages[PTE_PREFETCH_NUM]; struct kvm_memory_slot *slot; int i; if (WARN_ON_ONCE(nr_pages > PTE_PREFETCH_NUM)) return false; slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, access & ACC_WRITE_MASK); if (!slot) return false; nr_pages = kvm_prefetch_pages(slot, gfn, pages, nr_pages); if (nr_pages <= 0) return false; for (i = 0; i < nr_pages; i++, gfn++, sptep++) { mmu_set_spte(vcpu, slot, sptep, access, gfn, page_to_pfn(pages[i]), NULL); /* * KVM always prefetches writable pages from the primary MMU, * and KVM can make its SPTE writable in the fast page handler, * without notifying the primary MMU. Mark pages/folios dirty * now to ensure file data is written back if it ends up being * written by the guest. Because KVM's prefetching GUPs * writable PTEs, the probability of unnecessary writeback is * extremely low. */ kvm_release_page_dirty(pages[i]); } return true; } static bool direct_pte_prefetch_many(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, u64 *start, u64 *end) { gfn_t gfn = kvm_mmu_page_get_gfn(sp, spte_index(start)); unsigned int access = sp->role.access; return kvm_mmu_prefetch_sptes(vcpu, gfn, start, end - start, access); } static void __direct_pte_prefetch(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, u64 *sptep) { u64 *spte, *start = NULL; int i; WARN_ON_ONCE(!sp->role.direct); i = spte_index(sptep) & ~(PTE_PREFETCH_NUM - 1); spte = sp->spt + i; for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) { if (is_shadow_present_pte(*spte) || spte == sptep) { if (!start) continue; if (!direct_pte_prefetch_many(vcpu, sp, start, spte)) return; start = NULL; } else if (!start) start = spte; } if (start) direct_pte_prefetch_many(vcpu, sp, start, spte); } static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep) { struct kvm_mmu_page *sp; sp = sptep_to_sp(sptep); /* * Without accessed bits, there's no way to distinguish between * actually accessed translations and prefetched, so disable pte * prefetch if accessed bits aren't available. */ if (sp_ad_disabled(sp)) return; if (sp->role.level > PG_LEVEL_4K) return; /* * If addresses are being invalidated, skip prefetching to avoid * accidentally prefetching those addresses. */ if (unlikely(vcpu->kvm->mmu_invalidate_in_progress)) return; __direct_pte_prefetch(vcpu, sp, sptep); } /* * Lookup the mapping level for @gfn in the current mm. * * WARNING! Use of host_pfn_mapping_level() requires the caller and the end * consumer to be tied into KVM's handlers for MMU notifier events! * * There are several ways to safely use this helper: * * - Check mmu_invalidate_retry_gfn() after grabbing the mapping level, before * consuming it. In this case, mmu_lock doesn't need to be held during the * lookup, but it does need to be held while checking the MMU notifier. * * - Hold mmu_lock AND ensure there is no in-progress MMU notifier invalidation * event for the hva. This can be done by explicit checking the MMU notifier * or by ensuring that KVM already has a valid mapping that covers the hva. * * - Do not use the result to install new mappings, e.g. use the host mapping * level only to decide whether or not to zap an entry. In this case, it's * not required to hold mmu_lock (though it's highly likely the caller will * want to hold mmu_lock anyways, e.g. to modify SPTEs). * * Note! The lookup can still race with modifications to host page tables, but * the above "rules" ensure KVM will not _consume_ the result of the walk if a * race with the primary MMU occurs. */ static int host_pfn_mapping_level(struct kvm *kvm, gfn_t gfn, const struct kvm_memory_slot *slot) { int level = PG_LEVEL_4K; unsigned long hva; unsigned long flags; pgd_t pgd; p4d_t p4d; pud_t pud; pmd_t pmd; /* * Note, using the already-retrieved memslot and __gfn_to_hva_memslot() * is not solely for performance, it's also necessary to avoid the * "writable" check in __gfn_to_hva_many(), which will always fail on * read-only memslots due to gfn_to_hva() assuming writes. Earlier * page fault steps have already verified the guest isn't writing a * read-only memslot. */ hva = __gfn_to_hva_memslot(slot, gfn); /* * Disable IRQs to prevent concurrent tear down of host page tables, * e.g. if the primary MMU promotes a P*D to a huge page and then frees * the original page table. */ local_irq_save(flags); /* * Read each entry once. As above, a non-leaf entry can be promoted to * a huge page _during_ this walk. Re-reading the entry could send the * walk into the weeks, e.g. p*d_leaf() returns false (sees the old * value) and then p*d_offset() walks into the target huge page instead * of the old page table (sees the new value). */ pgd = READ_ONCE(*pgd_offset(kvm->mm, hva)); if (pgd_none(pgd)) goto out; p4d = READ_ONCE(*p4d_offset(&pgd, hva)); if (p4d_none(p4d) || !p4d_present(p4d)) goto out; pud = READ_ONCE(*pud_offset(&p4d, hva)); if (pud_none(pud) || !pud_present(pud)) goto out; if (pud_leaf(pud)) { level = PG_LEVEL_1G; goto out; } pmd = READ_ONCE(*pmd_offset(&pud, hva)); if (pmd_none(pmd) || !pmd_present(pmd)) goto out; if (pmd_leaf(pmd)) level = PG_LEVEL_2M; out: local_irq_restore(flags); return level; } static int __kvm_mmu_max_mapping_level(struct kvm *kvm, const struct kvm_memory_slot *slot, gfn_t gfn, int max_level, bool is_private) { struct kvm_lpage_info *linfo; int host_level; max_level = min(max_level, max_huge_page_level); for ( ; max_level > PG_LEVEL_4K; max_level--) { linfo = lpage_info_slot(gfn, slot, max_level); if (!linfo->disallow_lpage) break; } if (is_private) return max_level; if (max_level == PG_LEVEL_4K) return PG_LEVEL_4K; host_level = host_pfn_mapping_level(kvm, gfn, slot); return min(host_level, max_level); } int kvm_mmu_max_mapping_level(struct kvm *kvm, const struct kvm_memory_slot *slot, gfn_t gfn) { bool is_private = kvm_slot_can_be_private(slot) && kvm_mem_is_private(kvm, gfn); return __kvm_mmu_max_mapping_level(kvm, slot, gfn, PG_LEVEL_NUM, is_private); } void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { struct kvm_memory_slot *slot = fault->slot; kvm_pfn_t mask; fault->huge_page_disallowed = fault->exec && fault->nx_huge_page_workaround_enabled; if (unlikely(fault->max_level == PG_LEVEL_4K)) return; if (is_error_noslot_pfn(fault->pfn)) return; if (kvm_slot_dirty_track_enabled(slot)) return; /* * Enforce the iTLB multihit workaround after capturing the requested * level, which will be used to do precise, accurate accounting. */ fault->req_level = __kvm_mmu_max_mapping_level(vcpu->kvm, slot, fault->gfn, fault->max_level, fault->is_private); if (fault->req_level == PG_LEVEL_4K || fault->huge_page_disallowed) return; /* * mmu_invalidate_retry() was successful and mmu_lock is held, so * the pmd can't be split from under us. */ fault->goal_level = fault->req_level; mask = KVM_PAGES_PER_HPAGE(fault->goal_level) - 1; VM_BUG_ON((fault->gfn & mask) != (fault->pfn & mask)); fault->pfn &= ~mask; } void disallowed_hugepage_adjust(struct kvm_page_fault *fault, u64 spte, int cur_level) { if (cur_level > PG_LEVEL_4K && cur_level == fault->goal_level && is_shadow_present_pte(spte) && !is_large_pte(spte) && spte_to_child_sp(spte)->nx_huge_page_disallowed) { /* * A small SPTE exists for this pfn, but FNAME(fetch), * direct_map(), or kvm_tdp_mmu_map() would like to create a * large PTE instead: just force them to go down another level, * patching back for them into pfn the next 9 bits of the * address. */ u64 page_mask = KVM_PAGES_PER_HPAGE(cur_level) - KVM_PAGES_PER_HPAGE(cur_level - 1); fault->pfn |= fault->gfn & page_mask; fault->goal_level--; } } static int direct_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { struct kvm_shadow_walk_iterator it; struct kvm_mmu_page *sp; int ret; gfn_t base_gfn = fault->gfn; kvm_mmu_hugepage_adjust(vcpu, fault); trace_kvm_mmu_spte_requested(fault); for_each_shadow_entry(vcpu, fault->addr, it) { /* * We cannot overwrite existing page tables with an NX * large page, as the leaf could be executable. */ if (fault->nx_huge_page_workaround_enabled) disallowed_hugepage_adjust(fault, *it.sptep, it.level); base_gfn = gfn_round_for_level(fault->gfn, it.level); if (it.level == fault->goal_level) break; sp = kvm_mmu_get_child_sp(vcpu, it.sptep, base_gfn, true, ACC_ALL); if (sp == ERR_PTR(-EEXIST)) continue; link_shadow_page(vcpu, it.sptep, sp); if (fault->huge_page_disallowed) account_nx_huge_page(vcpu->kvm, sp, fault->req_level >= it.level); } if (WARN_ON_ONCE(it.level != fault->goal_level)) return -EFAULT; ret = mmu_set_spte(vcpu, fault->slot, it.sptep, ACC_ALL, base_gfn, fault->pfn, fault); if (ret == RET_PF_SPURIOUS) return ret; direct_pte_prefetch(vcpu, it.sptep); return ret; } static void kvm_send_hwpoison_signal(struct kvm_memory_slot *slot, gfn_t gfn) { unsigned long hva = gfn_to_hva_memslot(slot, gfn); send_sig_mceerr(BUS_MCEERR_AR, (void __user *)hva, PAGE_SHIFT, current); } static int kvm_handle_error_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { if (is_sigpending_pfn(fault->pfn)) { kvm_handle_signal_exit(vcpu); return -EINTR; } /* * Do not cache the mmio info caused by writing the readonly gfn * into the spte otherwise read access on readonly gfn also can * caused mmio page fault and treat it as mmio access. */ if (fault->pfn == KVM_PFN_ERR_RO_FAULT) return RET_PF_EMULATE; if (fault->pfn == KVM_PFN_ERR_HWPOISON) { kvm_send_hwpoison_signal(fault->slot, fault->gfn); return RET_PF_RETRY; } return -EFAULT; } static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, unsigned int access) { gva_t gva = fault->is_tdp ? 0 : fault->addr; if (fault->is_private) { kvm_mmu_prepare_memory_fault_exit(vcpu, fault); return -EFAULT; } vcpu_cache_mmio_info(vcpu, gva, fault->gfn, access & shadow_mmio_access_mask); fault->slot = NULL; fault->pfn = KVM_PFN_NOSLOT; fault->map_writable = false; /* * If MMIO caching is disabled, emulate immediately without * touching the shadow page tables as attempting to install an * MMIO SPTE will just be an expensive nop. */ if (unlikely(!enable_mmio_caching)) return RET_PF_EMULATE; /* * Do not create an MMIO SPTE for a gfn greater than host.MAXPHYADDR, * any guest that generates such gfns is running nested and is being * tricked by L0 userspace (you can observe gfn > L1.MAXPHYADDR if and * only if L1's MAXPHYADDR is inaccurate with respect to the * hardware's). */ if (unlikely(fault->gfn > kvm_mmu_max_gfn())) return RET_PF_EMULATE; return RET_PF_CONTINUE; } static bool page_fault_can_be_fast(struct kvm *kvm, struct kvm_page_fault *fault) { /* * Page faults with reserved bits set, i.e. faults on MMIO SPTEs, only * reach the common page fault handler if the SPTE has an invalid MMIO * generation number. Refreshing the MMIO generation needs to go down * the slow path. Note, EPT Misconfigs do NOT set the PRESENT flag! */ if (fault->rsvd) return false; /* * For hardware-protected VMs, certain conditions like attempting to * perform a write to a page which is not in the state that the guest * expects it to be in can result in a nested/extended #PF. In this * case, the below code might misconstrue this situation as being the * result of a write-protected access, and treat it as a spurious case * rather than taking any action to satisfy the real source of the #PF * such as generating a KVM_EXIT_MEMORY_FAULT. This can lead to the * guest spinning on a #PF indefinitely, so don't attempt the fast path * in this case. * * Note that the kvm_mem_is_private() check might race with an * attribute update, but this will either result in the guest spinning * on RET_PF_SPURIOUS until the update completes, or an actual spurious * case might go down the slow path. Either case will resolve itself. */ if (kvm->arch.has_private_mem && fault->is_private != kvm_mem_is_private(kvm, fault->gfn)) return false; /* * #PF can be fast if: * * 1. The shadow page table entry is not present and A/D bits are * disabled _by KVM_, which could mean that the fault is potentially * caused by access tracking (if enabled). If A/D bits are enabled * by KVM, but disabled by L1 for L2, KVM is forced to disable A/D * bits for L2 and employ access tracking, but the fast page fault * mechanism only supports direct MMUs. * 2. The shadow page table entry is present, the access is a write, * and no reserved bits are set (MMIO SPTEs cannot be "fixed"), i.e. * the fault was caused by a write-protection violation. If the * SPTE is MMU-writable (determined later), the fault can be fixed * by setting the Writable bit, which can be done out of mmu_lock. */ if (!fault->present) return !kvm_ad_enabled; /* * Note, instruction fetches and writes are mutually exclusive, ignore * the "exec" flag. */ return fault->write; } /* * Returns true if the SPTE was fixed successfully. Otherwise, * someone else modified the SPTE from its original value. */ static bool fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, u64 *sptep, u64 old_spte, u64 new_spte) { /* * Theoretically we could also set dirty bit (and flush TLB) here in * order to eliminate unnecessary PML logging. See comments in * set_spte. But fast_page_fault is very unlikely to happen with PML * enabled, so we do not do this. This might result in the same GPA * to be logged in PML buffer again when the write really happens, and * eventually to be called by mark_page_dirty twice. But it's also no * harm. This also avoids the TLB flush needed after setting dirty bit * so non-PML cases won't be impacted. * * Compare with make_spte() where instead shadow_dirty_mask is set. */ if (!try_cmpxchg64(sptep, &old_spte, new_spte)) return false; if (is_writable_pte(new_spte) && !is_writable_pte(old_spte)) mark_page_dirty_in_slot(vcpu->kvm, fault->slot, fault->gfn); return true; } /* * Returns the last level spte pointer of the shadow page walk for the given * gpa, and sets *spte to the spte value. This spte may be non-preset. If no * walk could be performed, returns NULL and *spte does not contain valid data. * * Contract: * - Must be called between walk_shadow_page_lockless_{begin,end}. * - The returned sptep must not be used after walk_shadow_page_lockless_end. */ static u64 *fast_pf_get_last_sptep(struct kvm_vcpu *vcpu, gpa_t gpa, u64 *spte) { struct kvm_shadow_walk_iterator iterator; u64 old_spte; u64 *sptep = NULL; for_each_shadow_entry_lockless(vcpu, gpa, iterator, old_spte) { sptep = iterator.sptep; *spte = old_spte; } return sptep; } /* * Returns one of RET_PF_INVALID, RET_PF_FIXED or RET_PF_SPURIOUS. */ static int fast_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { struct kvm_mmu_page *sp; int ret = RET_PF_INVALID; u64 spte; u64 *sptep; uint retry_count = 0; if (!page_fault_can_be_fast(vcpu->kvm, fault)) return ret; walk_shadow_page_lockless_begin(vcpu); do { u64 new_spte; if (tdp_mmu_enabled) sptep = kvm_tdp_mmu_fast_pf_get_last_sptep(vcpu, fault->gfn, &spte); else sptep = fast_pf_get_last_sptep(vcpu, fault->addr, &spte); /* * It's entirely possible for the mapping to have been zapped * by a different task, but the root page should always be * available as the vCPU holds a reference to its root(s). */ if (WARN_ON_ONCE(!sptep)) spte = FROZEN_SPTE; if (!is_shadow_present_pte(spte)) break; sp = sptep_to_sp(sptep); if (!is_last_spte(spte, sp->role.level)) break; /* * Check whether the memory access that caused the fault would * still cause it if it were to be performed right now. If not, * then this is a spurious fault caused by TLB lazily flushed, * or some other CPU has already fixed the PTE after the * current CPU took the fault. * * Need not check the access of upper level table entries since * they are always ACC_ALL. */ if (is_access_allowed(fault, spte)) { ret = RET_PF_SPURIOUS; break; } new_spte = spte; /* * KVM only supports fixing page faults outside of MMU lock for * direct MMUs, nested MMUs are always indirect, and KVM always * uses A/D bits for non-nested MMUs. Thus, if A/D bits are * enabled, the SPTE can't be an access-tracked SPTE. */ if (unlikely(!kvm_ad_enabled) && is_access_track_spte(spte)) new_spte = restore_acc_track_spte(new_spte) | shadow_accessed_mask; /* * To keep things simple, only SPTEs that are MMU-writable can * be made fully writable outside of mmu_lock, e.g. only SPTEs * that were write-protected for dirty-logging or access * tracking are handled here. Don't bother checking if the * SPTE is writable to prioritize running with A/D bits enabled. * The is_access_allowed() check above handles the common case * of the fault being spurious, and the SPTE is known to be * shadow-present, i.e. except for access tracking restoration * making the new SPTE writable, the check is wasteful. */ if (fault->write && is_mmu_writable_spte(spte)) { new_spte |= PT_WRITABLE_MASK; /* * Do not fix write-permission on the large spte when * dirty logging is enabled. Since we only dirty the * first page into the dirty-bitmap in * fast_pf_fix_direct_spte(), other pages are missed * if its slot has dirty logging enabled. * * Instead, we let the slow page fault path create a * normal spte to fix the access. */ if (sp->role.level > PG_LEVEL_4K && kvm_slot_dirty_track_enabled(fault->slot)) break; } /* Verify that the fault can be handled in the fast path */ if (new_spte == spte || !is_access_allowed(fault, new_spte)) break; /* * Currently, fast page fault only works for direct mapping * since the gfn is not stable for indirect shadow page. See * Documentation/virt/kvm/locking.rst to get more detail. */ if (fast_pf_fix_direct_spte(vcpu, fault, sptep, spte, new_spte)) { ret = RET_PF_FIXED; break; } if (++retry_count > 4) { pr_warn_once("Fast #PF retrying more than 4 times.\n"); break; } } while (true); trace_fast_page_fault(vcpu, fault, sptep, spte, ret); walk_shadow_page_lockless_end(vcpu); if (ret != RET_PF_INVALID) vcpu->stat.pf_fast++; return ret; } static void mmu_free_root_page(struct kvm *kvm, hpa_t *root_hpa, struct list_head *invalid_list) { struct kvm_mmu_page *sp; if (!VALID_PAGE(*root_hpa)) return; sp = root_to_sp(*root_hpa); if (WARN_ON_ONCE(!sp)) return; if (is_tdp_mmu_page(sp)) { lockdep_assert_held_read(&kvm->mmu_lock); kvm_tdp_mmu_put_root(kvm, sp); } else { lockdep_assert_held_write(&kvm->mmu_lock); if (!--sp->root_count && sp->role.invalid) kvm_mmu_prepare_zap_page(kvm, sp, invalid_list); } *root_hpa = INVALID_PAGE; } /* roots_to_free must be some combination of the KVM_MMU_ROOT_* flags */ void kvm_mmu_free_roots(struct kvm *kvm, struct kvm_mmu *mmu, ulong roots_to_free) { bool is_tdp_mmu = tdp_mmu_enabled && mmu->root_role.direct; int i; LIST_HEAD(invalid_list); bool free_active_root; WARN_ON_ONCE(roots_to_free & ~KVM_MMU_ROOTS_ALL); BUILD_BUG_ON(KVM_MMU_NUM_PREV_ROOTS >= BITS_PER_LONG); /* Before acquiring the MMU lock, see if we need to do any real work. */ free_active_root = (roots_to_free & KVM_MMU_ROOT_CURRENT) && VALID_PAGE(mmu->root.hpa); if (!free_active_root) { for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) if ((roots_to_free & KVM_MMU_ROOT_PREVIOUS(i)) && VALID_PAGE(mmu->prev_roots[i].hpa)) break; if (i == KVM_MMU_NUM_PREV_ROOTS) return; } if (is_tdp_mmu) read_lock(&kvm->mmu_lock); else write_lock(&kvm->mmu_lock); for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) if (roots_to_free & KVM_MMU_ROOT_PREVIOUS(i)) mmu_free_root_page(kvm, &mmu->prev_roots[i].hpa, &invalid_list); if (free_active_root) { if (kvm_mmu_is_dummy_root(mmu->root.hpa)) { /* Nothing to cleanup for dummy roots. */ } else if (root_to_sp(mmu->root.hpa)) { mmu_free_root_page(kvm, &mmu->root.hpa, &invalid_list); } else if (mmu->pae_root) { for (i = 0; i < 4; ++i) { if (!IS_VALID_PAE_ROOT(mmu->pae_root[i])) continue; mmu_free_root_page(kvm, &mmu->pae_root[i], &invalid_list); mmu->pae_root[i] = INVALID_PAE_ROOT; } } mmu->root.hpa = INVALID_PAGE; mmu->root.pgd = 0; } if (is_tdp_mmu) { read_unlock(&kvm->mmu_lock); WARN_ON_ONCE(!list_empty(&invalid_list)); } else { kvm_mmu_commit_zap_page(kvm, &invalid_list); write_unlock(&kvm->mmu_lock); } } EXPORT_SYMBOL_GPL(kvm_mmu_free_roots); void kvm_mmu_free_guest_mode_roots(struct kvm *kvm, struct kvm_mmu *mmu) { unsigned long roots_to_free = 0; struct kvm_mmu_page *sp; hpa_t root_hpa; int i; /* * This should not be called while L2 is active, L2 can't invalidate * _only_ its own roots, e.g. INVVPID unconditionally exits. */ WARN_ON_ONCE(mmu->root_role.guest_mode); for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) { root_hpa = mmu->prev_roots[i].hpa; if (!VALID_PAGE(root_hpa)) continue; sp = root_to_sp(root_hpa); if (!sp || sp->role.guest_mode) roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i); } kvm_mmu_free_roots(kvm, mmu, roots_to_free); } EXPORT_SYMBOL_GPL(kvm_mmu_free_guest_mode_roots); static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, int quadrant, u8 level) { union kvm_mmu_page_role role = vcpu->arch.mmu->root_role; struct kvm_mmu_page *sp; role.level = level; role.quadrant = quadrant; WARN_ON_ONCE(quadrant && !role.has_4_byte_gpte); WARN_ON_ONCE(role.direct && role.has_4_byte_gpte); sp = kvm_mmu_get_shadow_page(vcpu, gfn, role); ++sp->root_count; return __pa(sp->spt); } static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu) { struct kvm_mmu *mmu = vcpu->arch.mmu; u8 shadow_root_level = mmu->root_role.level; hpa_t root; unsigned i; int r; if (tdp_mmu_enabled) return kvm_tdp_mmu_alloc_root(vcpu); write_lock(&vcpu->kvm->mmu_lock); r = make_mmu_pages_available(vcpu); if (r < 0) goto out_unlock; if (shadow_root_level >= PT64_ROOT_4LEVEL) { root = mmu_alloc_root(vcpu, 0, 0, shadow_root_level); mmu->root.hpa = root; } else if (shadow_root_level == PT32E_ROOT_LEVEL) { if (WARN_ON_ONCE(!mmu->pae_root)) { r = -EIO; goto out_unlock; } for (i = 0; i < 4; ++i) { WARN_ON_ONCE(IS_VALID_PAE_ROOT(mmu->pae_root[i])); root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT), 0, PT32_ROOT_LEVEL); mmu->pae_root[i] = root | PT_PRESENT_MASK | shadow_me_value; } mmu->root.hpa = __pa(mmu->pae_root); } else { WARN_ONCE(1, "Bad TDP root level = %d\n", shadow_root_level); r = -EIO; goto out_unlock; } /* root.pgd is ignored for direct MMUs. */ mmu->root.pgd = 0; out_unlock: write_unlock(&vcpu->kvm->mmu_lock); return r; } static int mmu_first_shadow_root_alloc(struct kvm *kvm) { struct kvm_memslots *slots; struct kvm_memory_slot *slot; int r = 0, i, bkt; /* * Check if this is the first shadow root being allocated before * taking the lock. */ if (kvm_shadow_root_allocated(kvm)) return 0; mutex_lock(&kvm->slots_arch_lock); /* Recheck, under the lock, whether this is the first shadow root. */ if (kvm_shadow_root_allocated(kvm)) goto out_unlock; /* * Check if anything actually needs to be allocated, e.g. all metadata * will be allocated upfront if TDP is disabled. */ if (kvm_memslots_have_rmaps(kvm) && kvm_page_track_write_tracking_enabled(kvm)) goto out_success; for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) { slots = __kvm_memslots(kvm, i); kvm_for_each_memslot(slot, bkt, slots) { /* * Both of these functions are no-ops if the target is * already allocated, so unconditionally calling both * is safe. Intentionally do NOT free allocations on * failure to avoid having to track which allocations * were made now versus when the memslot was created. * The metadata is guaranteed to be freed when the slot * is freed, and will be kept/used if userspace retries * KVM_RUN instead of killing the VM. */ r = memslot_rmap_alloc(slot, slot->npages); if (r) goto out_unlock; r = kvm_page_track_write_tracking_alloc(slot); if (r) goto out_unlock; } } /* * Ensure that shadow_root_allocated becomes true strictly after * all the related pointers are set. */ out_success: smp_store_release(&kvm->arch.shadow_root_allocated, true); out_unlock: mutex_unlock(&kvm->slots_arch_lock); return r; } static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) { struct kvm_mmu *mmu = vcpu->arch.mmu; u64 pdptrs[4], pm_mask; gfn_t root_gfn, root_pgd; int quadrant, i, r; hpa_t root; root_pgd = kvm_mmu_get_guest_pgd(vcpu, mmu); root_gfn = (root_pgd & __PT_BASE_ADDR_MASK) >> PAGE_SHIFT; if (!kvm_vcpu_is_visible_gfn(vcpu, root_gfn)) { mmu->root.hpa = kvm_mmu_get_dummy_root(); return 0; } /* * On SVM, reading PDPTRs might access guest memory, which might fault * and thus might sleep. Grab the PDPTRs before acquiring mmu_lock. */ if (mmu->cpu_role.base.level == PT32E_ROOT_LEVEL) { for (i = 0; i < 4; ++i) { pdptrs[i] = mmu->get_pdptr(vcpu, i); if (!(pdptrs[i] & PT_PRESENT_MASK)) continue; if (!kvm_vcpu_is_visible_gfn(vcpu, pdptrs[i] >> PAGE_SHIFT)) pdptrs[i] = 0; } } r = mmu_first_shadow_root_alloc(vcpu->kvm); if (r) return r; write_lock(&vcpu->kvm->mmu_lock); r = make_mmu_pages_available(vcpu); if (r < 0) goto out_unlock; /* * Do we shadow a long mode page table? If so we need to * write-protect the guests page table root. */ if (mmu->cpu_role.base.level >= PT64_ROOT_4LEVEL) { root = mmu_alloc_root(vcpu, root_gfn, 0, mmu->root_role.level); mmu->root.hpa = root; goto set_root_pgd; } if (WARN_ON_ONCE(!mmu->pae_root)) { r = -EIO; goto out_unlock; } /* * We shadow a 32 bit page table. This may be a legacy 2-level * or a PAE 3-level page table. In either case we need to be aware that * the shadow page table may be a PAE or a long mode page table. */ pm_mask = PT_PRESENT_MASK | shadow_me_value; if (mmu->root_role.level >= PT64_ROOT_4LEVEL) { pm_mask |= PT_ACCESSED_MASK | PT_WRITABLE_MASK | PT_USER_MASK; if (WARN_ON_ONCE(!mmu->pml4_root)) { r = -EIO; goto out_unlock; } mmu->pml4_root[0] = __pa(mmu->pae_root) | pm_mask; if (mmu->root_role.level == PT64_ROOT_5LEVEL) { if (WARN_ON_ONCE(!mmu->pml5_root)) { r = -EIO; goto out_unlock; } mmu->pml5_root[0] = __pa(mmu->pml4_root) | pm_mask; } } for (i = 0; i < 4; ++i) { WARN_ON_ONCE(IS_VALID_PAE_ROOT(mmu->pae_root[i])); if (mmu->cpu_role.base.level == PT32E_ROOT_LEVEL) { if (!(pdptrs[i] & PT_PRESENT_MASK)) { mmu->pae_root[i] = INVALID_PAE_ROOT; continue; } root_gfn = pdptrs[i] >> PAGE_SHIFT; } /* * If shadowing 32-bit non-PAE page tables, each PAE page * directory maps one quarter of the guest's non-PAE page * directory. Othwerise each PAE page direct shadows one guest * PAE page directory so that quadrant should be 0. */ quadrant = (mmu->cpu_role.base.level == PT32_ROOT_LEVEL) ? i : 0; root = mmu_alloc_root(vcpu, root_gfn, quadrant, PT32_ROOT_LEVEL); mmu->pae_root[i] = root | pm_mask; } if (mmu->root_role.level == PT64_ROOT_5LEVEL) mmu->root.hpa = __pa(mmu->pml5_root); else if (mmu->root_role.level == PT64_ROOT_4LEVEL) mmu->root.hpa = __pa(mmu->pml4_root); else mmu->root.hpa = __pa(mmu->pae_root); set_root_pgd: mmu->root.pgd = root_pgd; out_unlock: write_unlock(&vcpu->kvm->mmu_lock); return r; } static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu) { struct kvm_mmu *mmu = vcpu->arch.mmu; bool need_pml5 = mmu->root_role.level > PT64_ROOT_4LEVEL; u64 *pml5_root = NULL; u64 *pml4_root = NULL; u64 *pae_root; /* * When shadowing 32-bit or PAE NPT with 64-bit NPT, the PML4 and PDP * tables are allocated and initialized at root creation as there is no * equivalent level in the guest's NPT to shadow. Allocate the tables * on demand, as running a 32-bit L1 VMM on 64-bit KVM is very rare. */ if (mmu->root_role.direct || mmu->cpu_role.base.level >= PT64_ROOT_4LEVEL || mmu->root_role.level < PT64_ROOT_4LEVEL) return 0; /* * NPT, the only paging mode that uses this horror, uses a fixed number * of levels for the shadow page tables, e.g. all MMUs are 4-level or * all MMus are 5-level. Thus, this can safely require that pml5_root * is allocated if the other roots are valid and pml5 is needed, as any * prior MMU would also have required pml5. */ if (mmu->pae_root && mmu->pml4_root && (!need_pml5 || mmu->pml5_root)) return 0; /* * The special roots should always be allocated in concert. Yell and * bail if KVM ends up in a state where only one of the roots is valid. */ if (WARN_ON_ONCE(!tdp_enabled || mmu->pae_root || mmu->pml4_root || (need_pml5 && mmu->pml5_root))) return -EIO; /* * Unlike 32-bit NPT, the PDP table doesn't need to be in low mem, and * doesn't need to be decrypted. */ pae_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT); if (!pae_root) return -ENOMEM; #ifdef CONFIG_X86_64 pml4_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT); if (!pml4_root) goto err_pml4; if (need_pml5) { pml5_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT); if (!pml5_root) goto err_pml5; } #endif mmu->pae_root = pae_root; mmu->pml4_root = pml4_root; mmu->pml5_root = pml5_root; return 0; #ifdef CONFIG_X86_64 err_pml5: free_page((unsigned long)pml4_root); err_pml4: free_page((unsigned long)pae_root); return -ENOMEM; #endif } static bool is_unsync_root(hpa_t root) { struct kvm_mmu_page *sp; if (!VALID_PAGE(root) || kvm_mmu_is_dummy_root(root)) return false; /* * The read barrier orders the CPU's read of SPTE.W during the page table * walk before the reads of sp->unsync/sp->unsync_children here. * * Even if another CPU was marking the SP as unsync-ed simultaneously, * any guest page table changes are not guaranteed to be visible anyway * until this VCPU issues a TLB flush strictly after those changes are * made. We only need to ensure that the other CPU sets these flags * before any actual changes to the page tables are made. The comments * in mmu_try_to_unsync_pages() describe what could go wrong if this * requirement isn't satisfied. */ smp_rmb(); sp = root_to_sp(root); /* * PAE roots (somewhat arbitrarily) aren't backed by shadow pages, the * PDPTEs for a given PAE root need to be synchronized individually. */ if (WARN_ON_ONCE(!sp)) return false; if (sp->unsync || sp->unsync_children) return true; return false; } void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu) { int i; struct kvm_mmu_page *sp; if (vcpu->arch.mmu->root_role.direct) return; if (!VALID_PAGE(vcpu->arch.mmu->root.hpa)) return; vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY); if (vcpu->arch.mmu->cpu_role.base.level >= PT64_ROOT_4LEVEL) { hpa_t root = vcpu->arch.mmu->root.hpa; if (!is_unsync_root(root)) return; sp = root_to_sp(root); write_lock(&vcpu->kvm->mmu_lock); mmu_sync_children(vcpu, sp, true); write_unlock(&vcpu->kvm->mmu_lock); return; } write_lock(&vcpu->kvm->mmu_lock); for (i = 0; i < 4; ++i) { hpa_t root = vcpu->arch.mmu->pae_root[i]; if (IS_VALID_PAE_ROOT(root)) { sp = spte_to_child_sp(root); mmu_sync_children(vcpu, sp, true); } } write_unlock(&vcpu->kvm->mmu_lock); } void kvm_mmu_sync_prev_roots(struct kvm_vcpu *vcpu) { unsigned long roots_to_free = 0; int i; for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) if (is_unsync_root(vcpu->arch.mmu->prev_roots[i].hpa)) roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i); /* sync prev_roots by simply freeing them */ kvm_mmu_free_roots(vcpu->kvm, vcpu->arch.mmu, roots_to_free); } static gpa_t nonpaging_gva_to_gpa(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, gpa_t vaddr, u64 access, struct x86_exception *exception) { if (exception) exception->error_code = 0; return kvm_translate_gpa(vcpu, mmu, vaddr, access, exception); } static bool mmio_info_in_cache(struct kvm_vcpu *vcpu, u64 addr, bool direct) { /* * A nested guest cannot use the MMIO cache if it is using nested * page tables, because cr2 is a nGPA while the cache stores GPAs. */ if (mmu_is_nested(vcpu)) return false; if (direct) return vcpu_match_mmio_gpa(vcpu, addr); return vcpu_match_mmio_gva(vcpu, addr); } /* * Return the level of the lowest level SPTE added to sptes. * That SPTE may be non-present. * * Must be called between walk_shadow_page_lockless_{begin,end}. */ static int get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, int *root_level) { struct kvm_shadow_walk_iterator iterator; int leaf = -1; u64 spte; for (shadow_walk_init(&iterator, vcpu, addr), *root_level = iterator.level; shadow_walk_okay(&iterator); __shadow_walk_next(&iterator, spte)) { leaf = iterator.level; spte = mmu_spte_get_lockless(iterator.sptep); sptes[leaf] = spte; } return leaf; } static int get_sptes_lockless(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, int *root_level) { int leaf; walk_shadow_page_lockless_begin(vcpu); if (is_tdp_mmu_active(vcpu)) leaf = kvm_tdp_mmu_get_walk(vcpu, addr, sptes, root_level); else leaf = get_walk(vcpu, addr, sptes, root_level); walk_shadow_page_lockless_end(vcpu); return leaf; } /* return true if reserved bit(s) are detected on a valid, non-MMIO SPTE. */ static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep) { u64 sptes[PT64_ROOT_MAX_LEVEL + 1]; struct rsvd_bits_validate *rsvd_check; int root, leaf, level; bool reserved = false; leaf = get_sptes_lockless(vcpu, addr, sptes, &root); if (unlikely(leaf < 0)) { *sptep = 0ull; return reserved; } *sptep = sptes[leaf]; /* * Skip reserved bits checks on the terminal leaf if it's not a valid * SPTE. Note, this also (intentionally) skips MMIO SPTEs, which, by * design, always have reserved bits set. The purpose of the checks is * to detect reserved bits on non-MMIO SPTEs. i.e. buggy SPTEs. */ if (!is_shadow_present_pte(sptes[leaf])) leaf++; rsvd_check = &vcpu->arch.mmu->shadow_zero_check; for (level = root; level >= leaf; level--) reserved |= is_rsvd_spte(rsvd_check, sptes[level], level); if (reserved) { pr_err("%s: reserved bits set on MMU-present spte, addr 0x%llx, hierarchy:\n", __func__, addr); for (level = root; level >= leaf; level--) pr_err("------ spte = 0x%llx level = %d, rsvd bits = 0x%llx", sptes[level], level, get_rsvd_bits(rsvd_check, sptes[level], level)); } return reserved; } static int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr, bool direct) { u64 spte; bool reserved; if (mmio_info_in_cache(vcpu, addr, direct)) return RET_PF_EMULATE; reserved = get_mmio_spte(vcpu, addr, &spte); if (WARN_ON_ONCE(reserved)) return -EINVAL; if (is_mmio_spte(vcpu->kvm, spte)) { gfn_t gfn = get_mmio_spte_gfn(spte); unsigned int access = get_mmio_spte_access(spte); if (!check_mmio_spte(vcpu, spte)) return RET_PF_INVALID; if (direct) addr = 0; trace_handle_mmio_page_fault(addr, gfn, access); vcpu_cache_mmio_info(vcpu, addr, gfn, access); return RET_PF_EMULATE; } /* * If the page table is zapped by other cpus, let CPU fault again on * the address. */ return RET_PF_RETRY; } static bool page_fault_handle_page_track(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { if (unlikely(fault->rsvd)) return false; if (!fault->present || !fault->write) return false; /* * guest is writing the page which is write tracked which can * not be fixed by page fault handler. */ if (kvm_gfn_is_write_tracked(vcpu->kvm, fault->slot, fault->gfn)) return true; return false; } static void shadow_page_table_clear_flood(struct kvm_vcpu *vcpu, gva_t addr) { struct kvm_shadow_walk_iterator iterator; u64 spte; walk_shadow_page_lockless_begin(vcpu); for_each_shadow_entry_lockless(vcpu, addr, iterator, spte) clear_sp_write_flooding_count(iterator.sptep); walk_shadow_page_lockless_end(vcpu); } static u32 alloc_apf_token(struct kvm_vcpu *vcpu) { /* make sure the token value is not 0 */ u32 id = vcpu->arch.apf.id; if (id << 12 == 0) vcpu->arch.apf.id = 1; return (vcpu->arch.apf.id++ << 12) | vcpu->vcpu_id; } static bool kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { struct kvm_arch_async_pf arch; arch.token = alloc_apf_token(vcpu); arch.gfn = fault->gfn; arch.error_code = fault->error_code; arch.direct_map = vcpu->arch.mmu->root_role.direct; arch.cr3 = kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu); return kvm_setup_async_pf(vcpu, fault->addr, kvm_vcpu_gfn_to_hva(vcpu, fault->gfn), &arch); } void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work) { int r; if (WARN_ON_ONCE(work->arch.error_code & PFERR_PRIVATE_ACCESS)) return; if ((vcpu->arch.mmu->root_role.direct != work->arch.direct_map) || work->wakeup_all) return; r = kvm_mmu_reload(vcpu); if (unlikely(r)) return; if (!vcpu->arch.mmu->root_role.direct && work->arch.cr3 != kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu)) return; r = kvm_mmu_do_page_fault(vcpu, work->cr2_or_gpa, work->arch.error_code, true, NULL, NULL); /* * Account fixed page faults, otherwise they'll never be counted, but * ignore stats for all other return times. Page-ready "faults" aren't * truly spurious and never trigger emulation */ if (r == RET_PF_FIXED) vcpu->stat.pf_fixed++; } static inline u8 kvm_max_level_for_order(int order) { BUILD_BUG_ON(KVM_MAX_HUGEPAGE_LEVEL > PG_LEVEL_1G); KVM_MMU_WARN_ON(order != KVM_HPAGE_GFN_SHIFT(PG_LEVEL_1G) && order != KVM_HPAGE_GFN_SHIFT(PG_LEVEL_2M) && order != KVM_HPAGE_GFN_SHIFT(PG_LEVEL_4K)); if (order >= KVM_HPAGE_GFN_SHIFT(PG_LEVEL_1G)) return PG_LEVEL_1G; if (order >= KVM_HPAGE_GFN_SHIFT(PG_LEVEL_2M)) return PG_LEVEL_2M; return PG_LEVEL_4K; } static u8 kvm_max_private_mapping_level(struct kvm *kvm, kvm_pfn_t pfn, u8 max_level, int gmem_order) { u8 req_max_level; if (max_level == PG_LEVEL_4K) return PG_LEVEL_4K; max_level = min(kvm_max_level_for_order(gmem_order), max_level); if (max_level == PG_LEVEL_4K) return PG_LEVEL_4K; req_max_level = kvm_x86_call(private_max_mapping_level)(kvm, pfn); if (req_max_level) max_level = min(max_level, req_max_level); return max_level; } static void kvm_mmu_finish_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, int r) { kvm_release_faultin_page(vcpu->kvm, fault->refcounted_page, r == RET_PF_RETRY, fault->map_writable); } static int kvm_mmu_faultin_pfn_private(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { int max_order, r; if (!kvm_slot_can_be_private(fault->slot)) { kvm_mmu_prepare_memory_fault_exit(vcpu, fault); return -EFAULT; } r = kvm_gmem_get_pfn(vcpu->kvm, fault->slot, fault->gfn, &fault->pfn, &fault->refcounted_page, &max_order); if (r) { kvm_mmu_prepare_memory_fault_exit(vcpu, fault); return r; } fault->map_writable = !(fault->slot->flags & KVM_MEM_READONLY); fault->max_level = kvm_max_private_mapping_level(vcpu->kvm, fault->pfn, fault->max_level, max_order); return RET_PF_CONTINUE; } static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { unsigned int foll = fault->write ? FOLL_WRITE : 0; if (fault->is_private) return kvm_mmu_faultin_pfn_private(vcpu, fault); foll |= FOLL_NOWAIT; fault->pfn = __kvm_faultin_pfn(fault->slot, fault->gfn, foll, &fault->map_writable, &fault->refcounted_page); /* * If resolving the page failed because I/O is needed to fault-in the * page, then either set up an asynchronous #PF to do the I/O, or if * doing an async #PF isn't possible, retry with I/O allowed. All * other failures are terminal, i.e. retrying won't help. */ if (fault->pfn != KVM_PFN_ERR_NEEDS_IO) return RET_PF_CONTINUE; if (!fault->prefetch && kvm_can_do_async_pf(vcpu)) { trace_kvm_try_async_get_page(fault->addr, fault->gfn); if (kvm_find_async_pf_gfn(vcpu, fault->gfn)) { trace_kvm_async_pf_repeated_fault(fault->addr, fault->gfn); kvm_make_request(KVM_REQ_APF_HALT, vcpu); return RET_PF_RETRY; } else if (kvm_arch_setup_async_pf(vcpu, fault)) { return RET_PF_RETRY; } } /* * Allow gup to bail on pending non-fatal signals when it's also allowed * to wait for IO. Note, gup always bails if it is unable to quickly * get a page and a fatal signal, i.e. SIGKILL, is pending. */ foll |= FOLL_INTERRUPTIBLE; foll &= ~FOLL_NOWAIT; fault->pfn = __kvm_faultin_pfn(fault->slot, fault->gfn, foll, &fault->map_writable, &fault->refcounted_page); return RET_PF_CONTINUE; } static int kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, unsigned int access) { struct kvm_memory_slot *slot = fault->slot; int ret; /* * Note that the mmu_invalidate_seq also serves to detect a concurrent * change in attributes. is_page_fault_stale() will detect an * invalidation relate to fault->fn and resume the guest without * installing a mapping in the page tables. */ fault->mmu_seq = vcpu->kvm->mmu_invalidate_seq; smp_rmb(); /* * Now that we have a snapshot of mmu_invalidate_seq we can check for a * private vs. shared mismatch. */ if (fault->is_private != kvm_mem_is_private(vcpu->kvm, fault->gfn)) { kvm_mmu_prepare_memory_fault_exit(vcpu, fault); return -EFAULT; } if (unlikely(!slot)) return kvm_handle_noslot_fault(vcpu, fault, access); /* * Retry the page fault if the gfn hit a memslot that is being deleted * or moved. This ensures any existing SPTEs for the old memslot will * be zapped before KVM inserts a new MMIO SPTE for the gfn. */ if (slot->flags & KVM_MEMSLOT_INVALID) return RET_PF_RETRY; if (slot->id == APIC_ACCESS_PAGE_PRIVATE_MEMSLOT) { /* * Don't map L1's APIC access page into L2, KVM doesn't support * using APICv/AVIC to accelerate L2 accesses to L1's APIC, * i.e. the access needs to be emulated. Emulating access to * L1's APIC is also correct if L1 is accelerating L2's own * virtual APIC, but for some reason L1 also maps _L1's_ APIC * into L2. Note, vcpu_is_mmio_gpa() always treats access to * the APIC as MMIO. Allow an MMIO SPTE to be created, as KVM * uses different roots for L1 vs. L2, i.e. there is no danger * of breaking APICv/AVIC for L1. */ if (is_guest_mode(vcpu)) return kvm_handle_noslot_fault(vcpu, fault, access); /* * If the APIC access page exists but is disabled, go directly * to emulation without caching the MMIO access or creating a * MMIO SPTE. That way the cache doesn't need to be purged * when the AVIC is re-enabled. */ if (!kvm_apicv_activated(vcpu->kvm)) return RET_PF_EMULATE; } /* * Check for a relevant mmu_notifier invalidation event before getting * the pfn from the primary MMU, and before acquiring mmu_lock. * * For mmu_lock, if there is an in-progress invalidation and the kernel * allows preemption, the invalidation task may drop mmu_lock and yield * in response to mmu_lock being contended, which is *very* counter- * productive as this vCPU can't actually make forward progress until * the invalidation completes. * * Retrying now can also avoid unnessary lock contention in the primary * MMU, as the primary MMU doesn't necessarily hold a single lock for * the duration of the invalidation, i.e. faulting in a conflicting pfn * can cause the invalidation to take longer by holding locks that are * needed to complete the invalidation. * * Do the pre-check even for non-preemtible kernels, i.e. even if KVM * will never yield mmu_lock in response to contention, as this vCPU is * *guaranteed* to need to retry, i.e. waiting until mmu_lock is held * to detect retry guarantees the worst case latency for the vCPU. */ if (mmu_invalidate_retry_gfn_unsafe(vcpu->kvm, fault->mmu_seq, fault->gfn)) return RET_PF_RETRY; ret = __kvm_mmu_faultin_pfn(vcpu, fault); if (ret != RET_PF_CONTINUE) return ret; if (unlikely(is_error_pfn(fault->pfn))) return kvm_handle_error_pfn(vcpu, fault); if (WARN_ON_ONCE(!fault->slot || is_noslot_pfn(fault->pfn))) return kvm_handle_noslot_fault(vcpu, fault, access); /* * Check again for a relevant mmu_notifier invalidation event purely to * avoid contending mmu_lock. Most invalidations will be detected by * the previous check, but checking is extremely cheap relative to the * overall cost of failing to detect the invalidation until after * mmu_lock is acquired. */ if (mmu_invalidate_retry_gfn_unsafe(vcpu->kvm, fault->mmu_seq, fault->gfn)) { kvm_mmu_finish_page_fault(vcpu, fault, RET_PF_RETRY); return RET_PF_RETRY; } return RET_PF_CONTINUE; } /* * Returns true if the page fault is stale and needs to be retried, i.e. if the * root was invalidated by a memslot update or a relevant mmu_notifier fired. */ static bool is_page_fault_stale(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { struct kvm_mmu_page *sp = root_to_sp(vcpu->arch.mmu->root.hpa); /* Special roots, e.g. pae_root, are not backed by shadow pages. */ if (sp && is_obsolete_sp(vcpu->kvm, sp)) return true; /* * Roots without an associated shadow page are considered invalid if * there is a pending request to free obsolete roots. The request is * only a hint that the current root _may_ be obsolete and needs to be * reloaded, e.g. if the guest frees a PGD that KVM is tracking as a * previous root, then __kvm_mmu_prepare_zap_page() signals all vCPUs * to reload even if no vCPU is actively using the root. */ if (!sp && kvm_test_request(KVM_REQ_MMU_FREE_OBSOLETE_ROOTS, vcpu)) return true; /* * Check for a relevant mmu_notifier invalidation event one last time * now that mmu_lock is held, as the "unsafe" checks performed without * holding mmu_lock can get false negatives. */ return fault->slot && mmu_invalidate_retry_gfn(vcpu->kvm, fault->mmu_seq, fault->gfn); } static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { int r; /* Dummy roots are used only for shadowing bad guest roots. */ if (WARN_ON_ONCE(kvm_mmu_is_dummy_root(vcpu->arch.mmu->root.hpa))) return RET_PF_RETRY; if (page_fault_handle_page_track(vcpu, fault)) return RET_PF_WRITE_PROTECTED; r = fast_page_fault(vcpu, fault); if (r != RET_PF_INVALID) return r; r = mmu_topup_memory_caches(vcpu, false); if (r) return r; r = kvm_mmu_faultin_pfn(vcpu, fault, ACC_ALL); if (r != RET_PF_CONTINUE) return r; r = RET_PF_RETRY; write_lock(&vcpu->kvm->mmu_lock); if (is_page_fault_stale(vcpu, fault)) goto out_unlock; r = make_mmu_pages_available(vcpu); if (r) goto out_unlock; r = direct_map(vcpu, fault); out_unlock: kvm_mmu_finish_page_fault(vcpu, fault, r); write_unlock(&vcpu->kvm->mmu_lock); return r; } static int nonpaging_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { /* This path builds a PAE pagetable, we can map 2mb pages at maximum. */ fault->max_level = PG_LEVEL_2M; return direct_page_fault(vcpu, fault); } int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code, u64 fault_address, char *insn, int insn_len) { int r = 1; u32 flags = vcpu->arch.apf.host_apf_flags; #ifndef CONFIG_X86_64 /* A 64-bit CR2 should be impossible on 32-bit KVM. */ if (WARN_ON_ONCE(fault_address >> 32)) return -EFAULT; #endif /* * Legacy #PF exception only have a 32-bit error code. Simply drop the * upper bits as KVM doesn't use them for #PF (because they are never * set), and to ensure there are no collisions with KVM-defined bits. */ if (WARN_ON_ONCE(error_code >> 32)) error_code = lower_32_bits(error_code); /* * Restrict KVM-defined flags to bits 63:32 so that it's impossible for * them to conflict with #PF error codes, which are limited to 32 bits. */ BUILD_BUG_ON(lower_32_bits(PFERR_SYNTHETIC_MASK)); vcpu->arch.l1tf_flush_l1d = true; if (!flags) { trace_kvm_page_fault(vcpu, fault_address, error_code); r = kvm_mmu_page_fault(vcpu, fault_address, error_code, insn, insn_len); } else if (flags & KVM_PV_REASON_PAGE_NOT_PRESENT) { vcpu->arch.apf.host_apf_flags = 0; local_irq_disable(); kvm_async_pf_task_wait_schedule(fault_address); local_irq_enable(); } else { WARN_ONCE(1, "Unexpected host async PF flags: %x\n", flags); } return r; } EXPORT_SYMBOL_GPL(kvm_handle_page_fault); #ifdef CONFIG_X86_64 static int kvm_tdp_mmu_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { int r; if (page_fault_handle_page_track(vcpu, fault)) return RET_PF_WRITE_PROTECTED; r = fast_page_fault(vcpu, fault); if (r != RET_PF_INVALID) return r; r = mmu_topup_memory_caches(vcpu, false); if (r) return r; r = kvm_mmu_faultin_pfn(vcpu, fault, ACC_ALL); if (r != RET_PF_CONTINUE) return r; r = RET_PF_RETRY; read_lock(&vcpu->kvm->mmu_lock); if (is_page_fault_stale(vcpu, fault)) goto out_unlock; r = kvm_tdp_mmu_map(vcpu, fault); out_unlock: kvm_mmu_finish_page_fault(vcpu, fault, r); read_unlock(&vcpu->kvm->mmu_lock); return r; } #endif bool kvm_mmu_may_ignore_guest_pat(void) { /* * When EPT is enabled (shadow_memtype_mask is non-zero), and the VM * has non-coherent DMA (DMA doesn't snoop CPU caches), KVM's ABI is to * honor the memtype from the guest's PAT so that guest accesses to * memory that is DMA'd aren't cached against the guest's wishes. As a * result, KVM _may_ ignore guest PAT, whereas without non-coherent DMA, * KVM _always_ ignores guest PAT (when EPT is enabled). */ return shadow_memtype_mask; } int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { #ifdef CONFIG_X86_64 if (tdp_mmu_enabled) return kvm_tdp_mmu_page_fault(vcpu, fault); #endif return direct_page_fault(vcpu, fault); } static int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code, u8 *level) { int r; /* * Restrict to TDP page fault, since that's the only case where the MMU * is indexed by GPA. */ if (vcpu->arch.mmu->page_fault != kvm_tdp_page_fault) return -EOPNOTSUPP; do { if (signal_pending(current)) return -EINTR; cond_resched(); r = kvm_mmu_do_page_fault(vcpu, gpa, error_code, true, NULL, level); } while (r == RET_PF_RETRY); if (r < 0) return r; switch (r) { case RET_PF_FIXED: case RET_PF_SPURIOUS: case RET_PF_WRITE_PROTECTED: return 0; case RET_PF_EMULATE: return -ENOENT; case RET_PF_RETRY: case RET_PF_CONTINUE: case RET_PF_INVALID: default: WARN_ONCE(1, "could not fix page fault during prefault"); return -EIO; } } long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu, struct kvm_pre_fault_memory *range) { u64 error_code = PFERR_GUEST_FINAL_MASK; u8 level = PG_LEVEL_4K; u64 end; int r; if (!vcpu->kvm->arch.pre_fault_allowed) return -EOPNOTSUPP; /* * reload is efficient when called repeatedly, so we can do it on * every iteration. */ r = kvm_mmu_reload(vcpu); if (r) return r; if (kvm_arch_has_private_mem(vcpu->kvm) && kvm_mem_is_private(vcpu->kvm, gpa_to_gfn(range->gpa))) error_code |= PFERR_PRIVATE_ACCESS; /* * Shadow paging uses GVA for kvm page fault, so restrict to * two-dimensional paging. */ r = kvm_tdp_map_page(vcpu, range->gpa, error_code, &level); if (r < 0) return r; /* * If the mapping that covers range->gpa can use a huge page, it * may start below it or end after range->gpa + range->size. */ end = (range->gpa & KVM_HPAGE_MASK(level)) + KVM_HPAGE_SIZE(level); return min(range->size, end - range->gpa); } static void nonpaging_init_context(struct kvm_mmu *context) { context->page_fault = nonpaging_page_fault; context->gva_to_gpa = nonpaging_gva_to_gpa; context->sync_spte = NULL; } static inline bool is_root_usable(struct kvm_mmu_root_info *root, gpa_t pgd, union kvm_mmu_page_role role) { struct kvm_mmu_page *sp; if (!VALID_PAGE(root->hpa)) return false; if (!role.direct && pgd != root->pgd) return false; sp = root_to_sp(root->hpa); if (WARN_ON_ONCE(!sp)) return false; return role.word == sp->role.word; } /* * Find out if a previously cached root matching the new pgd/role is available, * and insert the current root as the MRU in the cache. * If a matching root is found, it is assigned to kvm_mmu->root and * true is returned. * If no match is found, kvm_mmu->root is left invalid, the LRU root is * evicted to make room for the current root, and false is returned. */ static bool cached_root_find_and_keep_current(struct kvm *kvm, struct kvm_mmu *mmu, gpa_t new_pgd, union kvm_mmu_page_role new_role) { uint i; if (is_root_usable(&mmu->root, new_pgd, new_role)) return true; for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) { /* * The swaps end up rotating the cache like this: * C 0 1 2 3 (on entry to the function) * 0 C 1 2 3 * 1 C 0 2 3 * 2 C 0 1 3 * 3 C 0 1 2 (on exit from the loop) */ swap(mmu->root, mmu->prev_roots[i]); if (is_root_usable(&mmu->root, new_pgd, new_role)) return true; } kvm_mmu_free_roots(kvm, mmu, KVM_MMU_ROOT_CURRENT); return false; } /* * Find out if a previously cached root matching the new pgd/role is available. * On entry, mmu->root is invalid. * If a matching root is found, it is assigned to kvm_mmu->root, the LRU entry * of the cache becomes invalid, and true is returned. * If no match is found, kvm_mmu->root is left invalid and false is returned. */ static bool cached_root_find_without_current(struct kvm *kvm, struct kvm_mmu *mmu, gpa_t new_pgd, union kvm_mmu_page_role new_role) { uint i; for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) if (is_root_usable(&mmu->prev_roots[i], new_pgd, new_role)) goto hit; return false; hit: swap(mmu->root, mmu->prev_roots[i]); /* Bubble up the remaining roots. */ for (; i < KVM_MMU_NUM_PREV_ROOTS - 1; i++) mmu->prev_roots[i] = mmu->prev_roots[i + 1]; mmu->prev_roots[i].hpa = INVALID_PAGE; return true; } static bool fast_pgd_switch(struct kvm *kvm, struct kvm_mmu *mmu, gpa_t new_pgd, union kvm_mmu_page_role new_role) { /* * Limit reuse to 64-bit hosts+VMs without "special" roots in order to * avoid having to deal with PDPTEs and other complexities. */ if (VALID_PAGE(mmu->root.hpa) && !root_to_sp(mmu->root.hpa)) kvm_mmu_free_roots(kvm, mmu, KVM_MMU_ROOT_CURRENT); if (VALID_PAGE(mmu->root.hpa)) return cached_root_find_and_keep_current(kvm, mmu, new_pgd, new_role); else return cached_root_find_without_current(kvm, mmu, new_pgd, new_role); } void kvm_mmu_new_pgd(struct kvm_vcpu *vcpu, gpa_t new_pgd) { struct kvm_mmu *mmu = vcpu->arch.mmu; union kvm_mmu_page_role new_role = mmu->root_role; /* * Return immediately if no usable root was found, kvm_mmu_reload() * will establish a valid root prior to the next VM-Enter. */ if (!fast_pgd_switch(vcpu->kvm, mmu, new_pgd, new_role)) return; /* * It's possible that the cached previous root page is obsolete because * of a change in the MMU generation number. However, changing the * generation number is accompanied by KVM_REQ_MMU_FREE_OBSOLETE_ROOTS, * which will free the root set here and allocate a new one. */ kvm_make_request(KVM_REQ_LOAD_MMU_PGD, vcpu); if (force_flush_and_sync_on_reuse) { kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); } /* * The last MMIO access's GVA and GPA are cached in the VCPU. When * switching to a new CR3, that GVA->GPA mapping may no longer be * valid. So clear any cached MMIO info even when we don't need to sync * the shadow page tables. */ vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY); /* * If this is a direct root page, it doesn't have a write flooding * count. Otherwise, clear the write flooding count. */ if (!new_role.direct) { struct kvm_mmu_page *sp = root_to_sp(vcpu->arch.mmu->root.hpa); if (!WARN_ON_ONCE(!sp)) __clear_sp_write_flooding_count(sp); } } EXPORT_SYMBOL_GPL(kvm_mmu_new_pgd); static bool sync_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, gfn_t gfn, unsigned int access) { if (unlikely(is_mmio_spte(vcpu->kvm, *sptep))) { if (gfn != get_mmio_spte_gfn(*sptep)) { mmu_spte_clear_no_track(sptep); return true; } mark_mmio_spte(vcpu, sptep, gfn, access); return true; } return false; } #define PTTYPE_EPT 18 /* arbitrary */ #define PTTYPE PTTYPE_EPT #include "paging_tmpl.h" #undef PTTYPE #define PTTYPE 64 #include "paging_tmpl.h" #undef PTTYPE #define PTTYPE 32 #include "paging_tmpl.h" #undef PTTYPE static void __reset_rsvds_bits_mask(struct rsvd_bits_validate *rsvd_check, u64 pa_bits_rsvd, int level, bool nx, bool gbpages, bool pse, bool amd) { u64 gbpages_bit_rsvd = 0; u64 nonleaf_bit8_rsvd = 0; u64 high_bits_rsvd; rsvd_check->bad_mt_xwr = 0; if (!gbpages) gbpages_bit_rsvd = rsvd_bits(7, 7); if (level == PT32E_ROOT_LEVEL) high_bits_rsvd = pa_bits_rsvd & rsvd_bits(0, 62); else high_bits_rsvd = pa_bits_rsvd & rsvd_bits(0, 51); /* Note, NX doesn't exist in PDPTEs, this is handled below. */ if (!nx) high_bits_rsvd |= rsvd_bits(63, 63); /* * Non-leaf PML4Es and PDPEs reserve bit 8 (which would be the G bit for * leaf entries) on AMD CPUs only. */ if (amd) nonleaf_bit8_rsvd = rsvd_bits(8, 8); switch (level) { case PT32_ROOT_LEVEL: /* no rsvd bits for 2 level 4K page table entries */ rsvd_check->rsvd_bits_mask[0][1] = 0; rsvd_check->rsvd_bits_mask[0][0] = 0; rsvd_check->rsvd_bits_mask[1][0] = rsvd_check->rsvd_bits_mask[0][0]; if (!pse) { rsvd_check->rsvd_bits_mask[1][1] = 0; break; } if (is_cpuid_PSE36()) /* 36bits PSE 4MB page */ rsvd_check->rsvd_bits_mask[1][1] = rsvd_bits(17, 21); else /* 32 bits PSE 4MB page */ rsvd_check->rsvd_bits_mask[1][1] = rsvd_bits(13, 21); break; case PT32E_ROOT_LEVEL: rsvd_check->rsvd_bits_mask[0][2] = rsvd_bits(63, 63) | high_bits_rsvd | rsvd_bits(5, 8) | rsvd_bits(1, 2); /* PDPTE */ rsvd_check->rsvd_bits_mask[0][1] = high_bits_rsvd; /* PDE */ rsvd_check->rsvd_bits_mask[0][0] = high_bits_rsvd; /* PTE */ rsvd_check->rsvd_bits_mask[1][1] = high_bits_rsvd | rsvd_bits(13, 20); /* large page */ rsvd_check->rsvd_bits_mask[1][0] = rsvd_check->rsvd_bits_mask[0][0]; break; case PT64_ROOT_5LEVEL: rsvd_check->rsvd_bits_mask[0][4] = high_bits_rsvd | nonleaf_bit8_rsvd | rsvd_bits(7, 7); rsvd_check->rsvd_bits_mask[1][4] = rsvd_check->rsvd_bits_mask[0][4]; fallthrough; case PT64_ROOT_4LEVEL: rsvd_check->rsvd_bits_mask[0][3] = high_bits_rsvd | nonleaf_bit8_rsvd | rsvd_bits(7, 7); rsvd_check->rsvd_bits_mask[0][2] = high_bits_rsvd | gbpages_bit_rsvd; rsvd_check->rsvd_bits_mask[0][1] = high_bits_rsvd; rsvd_check->rsvd_bits_mask[0][0] = high_bits_rsvd; rsvd_check->rsvd_bits_mask[1][3] = rsvd_check->rsvd_bits_mask[0][3]; rsvd_check->rsvd_bits_mask[1][2] = high_bits_rsvd | gbpages_bit_rsvd | rsvd_bits(13, 29); rsvd_check->rsvd_bits_mask[1][1] = high_bits_rsvd | rsvd_bits(13, 20); /* large page */ rsvd_check->rsvd_bits_mask[1][0] = rsvd_check->rsvd_bits_mask[0][0]; break; } } static void reset_guest_rsvds_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context) { __reset_rsvds_bits_mask(&context->guest_rsvd_check, vcpu->arch.reserved_gpa_bits, context->cpu_role.base.level, is_efer_nx(context), guest_can_use(vcpu, X86_FEATURE_GBPAGES), is_cr4_pse(context), guest_cpuid_is_amd_compatible(vcpu)); } static void __reset_rsvds_bits_mask_ept(struct rsvd_bits_validate *rsvd_check, u64 pa_bits_rsvd, bool execonly, int huge_page_level) { u64 high_bits_rsvd = pa_bits_rsvd & rsvd_bits(0, 51); u64 large_1g_rsvd = 0, large_2m_rsvd = 0; u64 bad_mt_xwr; if (huge_page_level < PG_LEVEL_1G) large_1g_rsvd = rsvd_bits(7, 7); if (huge_page_level < PG_LEVEL_2M) large_2m_rsvd = rsvd_bits(7, 7); rsvd_check->rsvd_bits_mask[0][4] = high_bits_rsvd | rsvd_bits(3, 7); rsvd_check->rsvd_bits_mask[0][3] = high_bits_rsvd | rsvd_bits(3, 7); rsvd_check->rsvd_bits_mask[0][2] = high_bits_rsvd | rsvd_bits(3, 6) | large_1g_rsvd; rsvd_check->rsvd_bits_mask[0][1] = high_bits_rsvd | rsvd_bits(3, 6) | large_2m_rsvd; rsvd_check->rsvd_bits_mask[0][0] = high_bits_rsvd; /* large page */ rsvd_check->rsvd_bits_mask[1][4] = rsvd_check->rsvd_bits_mask[0][4]; rsvd_check->rsvd_bits_mask[1][3] = rsvd_check->rsvd_bits_mask[0][3]; rsvd_check->rsvd_bits_mask[1][2] = high_bits_rsvd | rsvd_bits(12, 29) | large_1g_rsvd; rsvd_check->rsvd_bits_mask[1][1] = high_bits_rsvd | rsvd_bits(12, 20) | large_2m_rsvd; rsvd_check->rsvd_bits_mask[1][0] = rsvd_check->rsvd_bits_mask[0][0]; bad_mt_xwr = 0xFFull << (2 * 8); /* bits 3..5 must not be 2 */ bad_mt_xwr |= 0xFFull << (3 * 8); /* bits 3..5 must not be 3 */ bad_mt_xwr |= 0xFFull << (7 * 8); /* bits 3..5 must not be 7 */ bad_mt_xwr |= REPEAT_BYTE(1ull << 2); /* bits 0..2 must not be 010 */ bad_mt_xwr |= REPEAT_BYTE(1ull << 6); /* bits 0..2 must not be 110 */ if (!execonly) { /* bits 0..2 must not be 100 unless VMX capabilities allow it */ bad_mt_xwr |= REPEAT_BYTE(1ull << 4); } rsvd_check->bad_mt_xwr = bad_mt_xwr; } static void reset_rsvds_bits_mask_ept(struct kvm_vcpu *vcpu, struct kvm_mmu *context, bool execonly, int huge_page_level) { __reset_rsvds_bits_mask_ept(&context->guest_rsvd_check, vcpu->arch.reserved_gpa_bits, execonly, huge_page_level); } static inline u64 reserved_hpa_bits(void) { return rsvd_bits(kvm_host.maxphyaddr, 63); } /* * the page table on host is the shadow page table for the page * table in guest or amd nested guest, its mmu features completely * follow the features in guest. */ static void reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context) { /* @amd adds a check on bit of SPTEs, which KVM shouldn't use anyways. */ bool is_amd = true; /* KVM doesn't use 2-level page tables for the shadow MMU. */ bool is_pse = false; struct rsvd_bits_validate *shadow_zero_check; int i; WARN_ON_ONCE(context->root_role.level < PT32E_ROOT_LEVEL); shadow_zero_check = &context->shadow_zero_check; __reset_rsvds_bits_mask(shadow_zero_check, reserved_hpa_bits(), context->root_role.level, context->root_role.efer_nx, guest_can_use(vcpu, X86_FEATURE_GBPAGES), is_pse, is_amd); if (!shadow_me_mask) return; for (i = context->root_role.level; --i >= 0;) { /* * So far shadow_me_value is a constant during KVM's life * time. Bits in shadow_me_value are allowed to be set. * Bits in shadow_me_mask but not in shadow_me_value are * not allowed to be set. */ shadow_zero_check->rsvd_bits_mask[0][i] |= shadow_me_mask; shadow_zero_check->rsvd_bits_mask[1][i] |= shadow_me_mask; shadow_zero_check->rsvd_bits_mask[0][i] &= ~shadow_me_value; shadow_zero_check->rsvd_bits_mask[1][i] &= ~shadow_me_value; } } static inline bool boot_cpu_is_amd(void) { WARN_ON_ONCE(!tdp_enabled); return shadow_x_mask == 0; } /* * the direct page table on host, use as much mmu features as * possible, however, kvm currently does not do execution-protection. */ static void reset_tdp_shadow_zero_bits_mask(struct kvm_mmu *context) { struct rsvd_bits_validate *shadow_zero_check; int i; shadow_zero_check = &context->shadow_zero_check; if (boot_cpu_is_amd()) __reset_rsvds_bits_mask(shadow_zero_check, reserved_hpa_bits(), context->root_role.level, true, boot_cpu_has(X86_FEATURE_GBPAGES), false, true); else __reset_rsvds_bits_mask_ept(shadow_zero_check, reserved_hpa_bits(), false, max_huge_page_level); if (!shadow_me_mask) return; for (i = context->root_role.level; --i >= 0;) { shadow_zero_check->rsvd_bits_mask[0][i] &= ~shadow_me_mask; shadow_zero_check->rsvd_bits_mask[1][i] &= ~shadow_me_mask; } } /* * as the comments in reset_shadow_zero_bits_mask() except it * is the shadow page table for intel nested guest. */ static void reset_ept_shadow_zero_bits_mask(struct kvm_mmu *context, bool execonly) { __reset_rsvds_bits_mask_ept(&context->shadow_zero_check, reserved_hpa_bits(), execonly, max_huge_page_level); } #define BYTE_MASK(access) \ ((1 & (access) ? 2 : 0) | \ (2 & (access) ? 4 : 0) | \ (3 & (access) ? 8 : 0) | \ (4 & (access) ? 16 : 0) | \ (5 & (access) ? 32 : 0) | \ (6 & (access) ? 64 : 0) | \ (7 & (access) ? 128 : 0)) static void update_permission_bitmask(struct kvm_mmu *mmu, bool ept) { unsigned byte; const u8 x = BYTE_MASK(ACC_EXEC_MASK); const u8 w = BYTE_MASK(ACC_WRITE_MASK); const u8 u = BYTE_MASK(ACC_USER_MASK); bool cr4_smep = is_cr4_smep(mmu); bool cr4_smap = is_cr4_smap(mmu); bool cr0_wp = is_cr0_wp(mmu); bool efer_nx = is_efer_nx(mmu); for (byte = 0; byte < ARRAY_SIZE(mmu->permissions); ++byte) { unsigned pfec = byte << 1; /* * Each "*f" variable has a 1 bit for each UWX value * that causes a fault with the given PFEC. */ /* Faults from writes to non-writable pages */ u8 wf = (pfec & PFERR_WRITE_MASK) ? (u8)~w : 0; /* Faults from user mode accesses to supervisor pages */ u8 uf = (pfec & PFERR_USER_MASK) ? (u8)~u : 0; /* Faults from fetches of non-executable pages*/ u8 ff = (pfec & PFERR_FETCH_MASK) ? (u8)~x : 0; /* Faults from kernel mode fetches of user pages */ u8 smepf = 0; /* Faults from kernel mode accesses of user pages */ u8 smapf = 0; if (!ept) { /* Faults from kernel mode accesses to user pages */ u8 kf = (pfec & PFERR_USER_MASK) ? 0 : u; /* Not really needed: !nx will cause pte.nx to fault */ if (!efer_nx) ff = 0; /* Allow supervisor writes if !cr0.wp */ if (!cr0_wp) wf = (pfec & PFERR_USER_MASK) ? wf : 0; /* Disallow supervisor fetches of user code if cr4.smep */ if (cr4_smep) smepf = (pfec & PFERR_FETCH_MASK) ? kf : 0; /* * SMAP:kernel-mode data accesses from user-mode * mappings should fault. A fault is considered * as a SMAP violation if all of the following * conditions are true: * - X86_CR4_SMAP is set in CR4 * - A user page is accessed * - The access is not a fetch * - The access is supervisor mode * - If implicit supervisor access or X86_EFLAGS_AC is clear * * Here, we cover the first four conditions. * The fifth is computed dynamically in permission_fault(); * PFERR_RSVD_MASK bit will be set in PFEC if the access is * *not* subject to SMAP restrictions. */ if (cr4_smap) smapf = (pfec & (PFERR_RSVD_MASK|PFERR_FETCH_MASK)) ? 0 : kf; } mmu->permissions[byte] = ff | uf | wf | smepf | smapf; } } /* * PKU is an additional mechanism by which the paging controls access to * user-mode addresses based on the value in the PKRU register. Protection * key violations are reported through a bit in the page fault error code. * Unlike other bits of the error code, the PK bit is not known at the * call site of e.g. gva_to_gpa; it must be computed directly in * permission_fault based on two bits of PKRU, on some machine state (CR4, * CR0, EFER, CPL), and on other bits of the error code and the page tables. * * In particular the following conditions come from the error code, the * page tables and the machine state: * - PK is always zero unless CR4.PKE=1 and EFER.LMA=1 * - PK is always zero if RSVD=1 (reserved bit set) or F=1 (instruction fetch) * - PK is always zero if U=0 in the page tables * - PKRU.WD is ignored if CR0.WP=0 and the access is a supervisor access. * * The PKRU bitmask caches the result of these four conditions. The error * code (minus the P bit) and the page table's U bit form an index into the * PKRU bitmask. Two bits of the PKRU bitmask are then extracted and ANDed * with the two bits of the PKRU register corresponding to the protection key. * For the first three conditions above the bits will be 00, thus masking * away both AD and WD. For all reads or if the last condition holds, WD * only will be masked away. */ static void update_pkru_bitmask(struct kvm_mmu *mmu) { unsigned bit; bool wp; mmu->pkru_mask = 0; if (!is_cr4_pke(mmu)) return; wp = is_cr0_wp(mmu); for (bit = 0; bit < ARRAY_SIZE(mmu->permissions); ++bit) { unsigned pfec, pkey_bits; bool check_pkey, check_write, ff, uf, wf, pte_user; pfec = bit << 1; ff = pfec & PFERR_FETCH_MASK; uf = pfec & PFERR_USER_MASK; wf = pfec & PFERR_WRITE_MASK; /* PFEC.RSVD is replaced by ACC_USER_MASK. */ pte_user = pfec & PFERR_RSVD_MASK; /* * Only need to check the access which is not an * instruction fetch and is to a user page. */ check_pkey = (!ff && pte_user); /* * write access is controlled by PKRU if it is a * user access or CR0.WP = 1. */ check_write = check_pkey && wf && (uf || wp); /* PKRU.AD stops both read and write access. */ pkey_bits = !!check_pkey; /* PKRU.WD stops write access. */ pkey_bits |= (!!check_write) << 1; mmu->pkru_mask |= (pkey_bits & 3) << pfec; } } static void reset_guest_paging_metadata(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu) { if (!is_cr0_pg(mmu)) return; reset_guest_rsvds_bits_mask(vcpu, mmu); update_permission_bitmask(mmu, false); update_pkru_bitmask(mmu); } static void paging64_init_context(struct kvm_mmu *context) { context->page_fault = paging64_page_fault; context->gva_to_gpa = paging64_gva_to_gpa; context->sync_spte = paging64_sync_spte; } static void paging32_init_context(struct kvm_mmu *context) { context->page_fault = paging32_page_fault; context->gva_to_gpa = paging32_gva_to_gpa; context->sync_spte = paging32_sync_spte; } static union kvm_cpu_role kvm_calc_cpu_role(struct kvm_vcpu *vcpu, const struct kvm_mmu_role_regs *regs) { union kvm_cpu_role role = {0}; role.base.access = ACC_ALL; role.base.smm = is_smm(vcpu); role.base.guest_mode = is_guest_mode(vcpu); role.ext.valid = 1; if (!____is_cr0_pg(regs)) { role.base.direct = 1; return role; } role.base.efer_nx = ____is_efer_nx(regs); role.base.cr0_wp = ____is_cr0_wp(regs); role.base.smep_andnot_wp = ____is_cr4_smep(regs) && !____is_cr0_wp(regs); role.base.smap_andnot_wp = ____is_cr4_smap(regs) && !____is_cr0_wp(regs); role.base.has_4_byte_gpte = !____is_cr4_pae(regs); if (____is_efer_lma(regs)) role.base.level = ____is_cr4_la57(regs) ? PT64_ROOT_5LEVEL : PT64_ROOT_4LEVEL; else if (____is_cr4_pae(regs)) role.base.level = PT32E_ROOT_LEVEL; else role.base.level = PT32_ROOT_LEVEL; role.ext.cr4_smep = ____is_cr4_smep(regs); role.ext.cr4_smap = ____is_cr4_smap(regs); role.ext.cr4_pse = ____is_cr4_pse(regs); /* PKEY and LA57 are active iff long mode is active. */ role.ext.cr4_pke = ____is_efer_lma(regs) && ____is_cr4_pke(regs); role.ext.cr4_la57 = ____is_efer_lma(regs) && ____is_cr4_la57(regs); role.ext.efer_lma = ____is_efer_lma(regs); return role; } void __kvm_mmu_refresh_passthrough_bits(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu) { const bool cr0_wp = kvm_is_cr0_bit_set(vcpu, X86_CR0_WP); BUILD_BUG_ON((KVM_MMU_CR0_ROLE_BITS & KVM_POSSIBLE_CR0_GUEST_BITS) != X86_CR0_WP); BUILD_BUG_ON((KVM_MMU_CR4_ROLE_BITS & KVM_POSSIBLE_CR4_GUEST_BITS)); if (is_cr0_wp(mmu) == cr0_wp) return; mmu->cpu_role.base.cr0_wp = cr0_wp; reset_guest_paging_metadata(vcpu, mmu); } static inline int kvm_mmu_get_tdp_level(struct kvm_vcpu *vcpu) { /* tdp_root_level is architecture forced level, use it if nonzero */ if (tdp_root_level) return tdp_root_level; /* Use 5-level TDP if and only if it's useful/necessary. */ if (max_tdp_level == 5 && cpuid_maxphyaddr(vcpu) <= 48) return 4; return max_tdp_level; } u8 kvm_mmu_get_max_tdp_level(void) { return tdp_root_level ? tdp_root_level : max_tdp_level; } static union kvm_mmu_page_role kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu, union kvm_cpu_role cpu_role) { union kvm_mmu_page_role role = {0}; role.access = ACC_ALL; role.cr0_wp = true; role.efer_nx = true; role.smm = cpu_role.base.smm; role.guest_mode = cpu_role.base.guest_mode; role.ad_disabled = !kvm_ad_enabled; role.level = kvm_mmu_get_tdp_level(vcpu); role.direct = true; role.has_4_byte_gpte = false; return role; } static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu, union kvm_cpu_role cpu_role) { struct kvm_mmu *context = &vcpu->arch.root_mmu; union kvm_mmu_page_role root_role = kvm_calc_tdp_mmu_root_page_role(vcpu, cpu_role); if (cpu_role.as_u64 == context->cpu_role.as_u64 && root_role.word == context->root_role.word) return; context->cpu_role.as_u64 = cpu_role.as_u64; context->root_role.word = root_role.word; context->page_fault = kvm_tdp_page_fault; context->sync_spte = NULL; context->get_guest_pgd = get_guest_cr3; context->get_pdptr = kvm_pdptr_read; context->inject_page_fault = kvm_inject_page_fault; if (!is_cr0_pg(context)) context->gva_to_gpa = nonpaging_gva_to_gpa; else if (is_cr4_pae(context)) context->gva_to_gpa = paging64_gva_to_gpa; else context->gva_to_gpa = paging32_gva_to_gpa; reset_guest_paging_metadata(vcpu, context); reset_tdp_shadow_zero_bits_mask(context); } static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, struct kvm_mmu *context, union kvm_cpu_role cpu_role, union kvm_mmu_page_role root_role) { if (cpu_role.as_u64 == context->cpu_role.as_u64 && root_role.word == context->root_role.word) return; context->cpu_role.as_u64 = cpu_role.as_u64; context->root_role.word = root_role.word; if (!is_cr0_pg(context)) nonpaging_init_context(context); else if (is_cr4_pae(context)) paging64_init_context(context); else paging32_init_context(context); reset_guest_paging_metadata(vcpu, context); reset_shadow_zero_bits_mask(vcpu, context); } static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, union kvm_cpu_role cpu_role) { struct kvm_mmu *context = &vcpu->arch.root_mmu; union kvm_mmu_page_role root_role; root_role = cpu_role.base; /* KVM uses PAE paging whenever the guest isn't using 64-bit paging. */ root_role.level = max_t(u32, root_role.level, PT32E_ROOT_LEVEL); /* * KVM forces EFER.NX=1 when TDP is disabled, reflect it in the MMU role. * KVM uses NX when TDP is disabled to handle a variety of scenarios, * notably for huge SPTEs if iTLB multi-hit mitigation is enabled and * to generate correct permissions for CR0.WP=0/CR4.SMEP=1/EFER.NX=0. * The iTLB multi-hit workaround can be toggled at any time, so assume * NX can be used by any non-nested shadow MMU to avoid having to reset * MMU contexts. */ root_role.efer_nx = true; shadow_mmu_init_context(vcpu, context, cpu_role, root_role); } void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, unsigned long cr0, unsigned long cr4, u64 efer, gpa_t nested_cr3) { struct kvm_mmu *context = &vcpu->arch.guest_mmu; struct kvm_mmu_role_regs regs = { .cr0 = cr0, .cr4 = cr4 & ~X86_CR4_PKE, .efer = efer, }; union kvm_cpu_role cpu_role = kvm_calc_cpu_role(vcpu, ®s); union kvm_mmu_page_role root_role; /* NPT requires CR0.PG=1. */ WARN_ON_ONCE(cpu_role.base.direct); root_role = cpu_role.base; root_role.level = kvm_mmu_get_tdp_level(vcpu); if (root_role.level == PT64_ROOT_5LEVEL && cpu_role.base.level == PT64_ROOT_4LEVEL) root_role.passthrough = 1; shadow_mmu_init_context(vcpu, context, cpu_role, root_role); kvm_mmu_new_pgd(vcpu, nested_cr3); } EXPORT_SYMBOL_GPL(kvm_init_shadow_npt_mmu); static union kvm_cpu_role kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty, bool execonly, u8 level) { union kvm_cpu_role role = {0}; /* * KVM does not support SMM transfer monitors, and consequently does not * support the "entry to SMM" control either. role.base.smm is always 0. */ WARN_ON_ONCE(is_smm(vcpu)); role.base.level = level; role.base.has_4_byte_gpte = false; role.base.direct = false; role.base.ad_disabled = !accessed_dirty; role.base.guest_mode = true; role.base.access = ACC_ALL; role.ext.word = 0; role.ext.execonly = execonly; role.ext.valid = 1; return role; } void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly, int huge_page_level, bool accessed_dirty, gpa_t new_eptp) { struct kvm_mmu *context = &vcpu->arch.guest_mmu; u8 level = vmx_eptp_page_walk_level(new_eptp); union kvm_cpu_role new_mode = kvm_calc_shadow_ept_root_page_role(vcpu, accessed_dirty, execonly, level); if (new_mode.as_u64 != context->cpu_role.as_u64) { /* EPT, and thus nested EPT, does not consume CR0, CR4, nor EFER. */ context->cpu_role.as_u64 = new_mode.as_u64; context->root_role.word = new_mode.base.word; context->page_fault = ept_page_fault; context->gva_to_gpa = ept_gva_to_gpa; context->sync_spte = ept_sync_spte; update_permission_bitmask(context, true); context->pkru_mask = 0; reset_rsvds_bits_mask_ept(vcpu, context, execonly, huge_page_level); reset_ept_shadow_zero_bits_mask(context, execonly); } kvm_mmu_new_pgd(vcpu, new_eptp); } EXPORT_SYMBOL_GPL(kvm_init_shadow_ept_mmu); static void init_kvm_softmmu(struct kvm_vcpu *vcpu, union kvm_cpu_role cpu_role) { struct kvm_mmu *context = &vcpu->arch.root_mmu; kvm_init_shadow_mmu(vcpu, cpu_role); context->get_guest_pgd = get_guest_cr3; context->get_pdptr = kvm_pdptr_read; context->inject_page_fault = kvm_inject_page_fault; } static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu, union kvm_cpu_role new_mode) { struct kvm_mmu *g_context = &vcpu->arch.nested_mmu; if (new_mode.as_u64 == g_context->cpu_role.as_u64) return; g_context->cpu_role.as_u64 = new_mode.as_u64; g_context->get_guest_pgd = get_guest_cr3; g_context->get_pdptr = kvm_pdptr_read; g_context->inject_page_fault = kvm_inject_page_fault; /* * L2 page tables are never shadowed, so there is no need to sync * SPTEs. */ g_context->sync_spte = NULL; /* * Note that arch.mmu->gva_to_gpa translates l2_gpa to l1_gpa using * L1's nested page tables (e.g. EPT12). The nested translation * of l2_gva to l1_gpa is done by arch.nested_mmu.gva_to_gpa using * L2's page tables as the first level of translation and L1's * nested page tables as the second level of translation. Basically * the gva_to_gpa functions between mmu and nested_mmu are swapped. */ if (!is_paging(vcpu)) g_context->gva_to_gpa = nonpaging_gva_to_gpa; else if (is_long_mode(vcpu)) g_context->gva_to_gpa = paging64_gva_to_gpa; else if (is_pae(vcpu)) g_context->gva_to_gpa = paging64_gva_to_gpa; else g_context->gva_to_gpa = paging32_gva_to_gpa; reset_guest_paging_metadata(vcpu, g_context); } void kvm_init_mmu(struct kvm_vcpu *vcpu) { struct kvm_mmu_role_regs regs = vcpu_to_role_regs(vcpu); union kvm_cpu_role cpu_role = kvm_calc_cpu_role(vcpu, ®s); if (mmu_is_nested(vcpu)) init_kvm_nested_mmu(vcpu, cpu_role); else if (tdp_enabled) init_kvm_tdp_mmu(vcpu, cpu_role); else init_kvm_softmmu(vcpu, cpu_role); } EXPORT_SYMBOL_GPL(kvm_init_mmu); void kvm_mmu_after_set_cpuid(struct kvm_vcpu *vcpu) { /* * Invalidate all MMU roles to force them to reinitialize as CPUID * information is factored into reserved bit calculations. * * Correctly handling multiple vCPU models with respect to paging and * physical address properties) in a single VM would require tracking * all relevant CPUID information in kvm_mmu_page_role. That is very * undesirable as it would increase the memory requirements for * gfn_write_track (see struct kvm_mmu_page_role comments). For now * that problem is swept under the rug; KVM's CPUID API is horrific and * it's all but impossible to solve it without introducing a new API. */ vcpu->arch.root_mmu.root_role.invalid = 1; vcpu->arch.guest_mmu.root_role.invalid = 1; vcpu->arch.nested_mmu.root_role.invalid = 1; vcpu->arch.root_mmu.cpu_role.ext.valid = 0; vcpu->arch.guest_mmu.cpu_role.ext.valid = 0; vcpu->arch.nested_mmu.cpu_role.ext.valid = 0; kvm_mmu_reset_context(vcpu); /* * Changing guest CPUID after KVM_RUN is forbidden, see the comment in * kvm_arch_vcpu_ioctl(). */ KVM_BUG_ON(kvm_vcpu_has_run(vcpu), vcpu->kvm); } void kvm_mmu_reset_context(struct kvm_vcpu *vcpu) { kvm_mmu_unload(vcpu); kvm_init_mmu(vcpu); } EXPORT_SYMBOL_GPL(kvm_mmu_reset_context); int kvm_mmu_load(struct kvm_vcpu *vcpu) { int r; r = mmu_topup_memory_caches(vcpu, !vcpu->arch.mmu->root_role.direct); if (r) goto out; r = mmu_alloc_special_roots(vcpu); if (r) goto out; if (vcpu->arch.mmu->root_role.direct) r = mmu_alloc_direct_roots(vcpu); else r = mmu_alloc_shadow_roots(vcpu); if (r) goto out; kvm_mmu_sync_roots(vcpu); kvm_mmu_load_pgd(vcpu); /* * Flush any TLB entries for the new root, the provenance of the root * is unknown. Even if KVM ensures there are no stale TLB entries * for a freed root, in theory another hypervisor could have left * stale entries. Flushing on alloc also allows KVM to skip the TLB * flush when freeing a root (see kvm_tdp_mmu_put_root()). */ kvm_x86_call(flush_tlb_current)(vcpu); out: return r; } void kvm_mmu_unload(struct kvm_vcpu *vcpu) { struct kvm *kvm = vcpu->kvm; kvm_mmu_free_roots(kvm, &vcpu->arch.root_mmu, KVM_MMU_ROOTS_ALL); WARN_ON_ONCE(VALID_PAGE(vcpu->arch.root_mmu.root.hpa)); kvm_mmu_free_roots(kvm, &vcpu->arch.guest_mmu, KVM_MMU_ROOTS_ALL); WARN_ON_ONCE(VALID_PAGE(vcpu->arch.guest_mmu.root.hpa)); vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY); } static bool is_obsolete_root(struct kvm *kvm, hpa_t root_hpa) { struct kvm_mmu_page *sp; if (!VALID_PAGE(root_hpa)) return false; /* * When freeing obsolete roots, treat roots as obsolete if they don't * have an associated shadow page, as it's impossible to determine if * such roots are fresh or stale. This does mean KVM will get false * positives and free roots that don't strictly need to be freed, but * such false positives are relatively rare: * * (a) only PAE paging and nested NPT have roots without shadow pages * (or any shadow paging flavor with a dummy root, see note below) * (b) remote reloads due to a memslot update obsoletes _all_ roots * (c) KVM doesn't track previous roots for PAE paging, and the guest * is unlikely to zap an in-use PGD. * * Note! Dummy roots are unique in that they are obsoleted by memslot * _creation_! See also FNAME(fetch). */ sp = root_to_sp(root_hpa); return !sp || is_obsolete_sp(kvm, sp); } static void __kvm_mmu_free_obsolete_roots(struct kvm *kvm, struct kvm_mmu *mmu) { unsigned long roots_to_free = 0; int i; if (is_obsolete_root(kvm, mmu->root.hpa)) roots_to_free |= KVM_MMU_ROOT_CURRENT; for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) { if (is_obsolete_root(kvm, mmu->prev_roots[i].hpa)) roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i); } if (roots_to_free) kvm_mmu_free_roots(kvm, mmu, roots_to_free); } void kvm_mmu_free_obsolete_roots(struct kvm_vcpu *vcpu) { __kvm_mmu_free_obsolete_roots(vcpu->kvm, &vcpu->arch.root_mmu); __kvm_mmu_free_obsolete_roots(vcpu->kvm, &vcpu->arch.guest_mmu); } static u64 mmu_pte_write_fetch_gpte(struct kvm_vcpu *vcpu, gpa_t *gpa, int *bytes) { u64 gentry = 0; int r; /* * Assume that the pte write on a page table of the same type * as the current vcpu paging mode since we update the sptes only * when they have the same mode. */ if (is_pae(vcpu) && *bytes == 4) { /* Handle a 32-bit guest writing two halves of a 64-bit gpte */ *gpa &= ~(gpa_t)7; *bytes = 8; } if (*bytes == 4 || *bytes == 8) { r = kvm_vcpu_read_guest_atomic(vcpu, *gpa, &gentry, *bytes); if (r) gentry = 0; } return gentry; } /* * If we're seeing too many writes to a page, it may no longer be a page table, * or we may be forking, in which case it is better to unmap the page. */ static bool detect_write_flooding(struct kvm_mmu_page *sp) { /* * Skip write-flooding detected for the sp whose level is 1, because * it can become unsync, then the guest page is not write-protected. */ if (sp->role.level == PG_LEVEL_4K) return false; atomic_inc(&sp->write_flooding_count); return atomic_read(&sp->write_flooding_count) >= 3; } /* * Misaligned accesses are too much trouble to fix up; also, they usually * indicate a page is not used as a page table. */ static bool detect_write_misaligned(struct kvm_mmu_page *sp, gpa_t gpa, int bytes) { unsigned offset, pte_size, misaligned; offset = offset_in_page(gpa); pte_size = sp->role.has_4_byte_gpte ? 4 : 8; /* * Sometimes, the OS only writes the last one bytes to update status * bits, for example, in linux, andb instruction is used in clear_bit(). */ if (!(offset & (pte_size - 1)) && bytes == 1) return false; misaligned = (offset ^ (offset + bytes - 1)) & ~(pte_size - 1); misaligned |= bytes < 4; return misaligned; } static u64 *get_written_sptes(struct kvm_mmu_page *sp, gpa_t gpa, int *nspte) { unsigned page_offset, quadrant; u64 *spte; int level; page_offset = offset_in_page(gpa); level = sp->role.level; *nspte = 1; if (sp->role.has_4_byte_gpte) { page_offset <<= 1; /* 32->64 */ /* * A 32-bit pde maps 4MB while the shadow pdes map * only 2MB. So we need to double the offset again * and zap two pdes instead of one. */ if (level == PT32_ROOT_LEVEL) { page_offset &= ~7; /* kill rounding error */ page_offset <<= 1; *nspte = 2; } quadrant = page_offset >> PAGE_SHIFT; page_offset &= ~PAGE_MASK; if (quadrant != sp->role.quadrant) return NULL; } spte = &sp->spt[page_offset / sizeof(*spte)]; return spte; } void kvm_mmu_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new, int bytes) { gfn_t gfn = gpa >> PAGE_SHIFT; struct kvm_mmu_page *sp; LIST_HEAD(invalid_list); u64 entry, gentry, *spte; int npte; bool flush = false; /* * When emulating guest writes, ensure the written value is visible to * any task that is handling page faults before checking whether or not * KVM is shadowing a guest PTE. This ensures either KVM will create * the correct SPTE in the page fault handler, or this task will see * a non-zero indirect_shadow_pages. Pairs with the smp_mb() in * account_shadowed(). */ smp_mb(); if (!vcpu->kvm->arch.indirect_shadow_pages) return; write_lock(&vcpu->kvm->mmu_lock); gentry = mmu_pte_write_fetch_gpte(vcpu, &gpa, &bytes); ++vcpu->kvm->stat.mmu_pte_write; for_each_gfn_valid_sp_with_gptes(vcpu->kvm, sp, gfn) { if (detect_write_misaligned(sp, gpa, bytes) || detect_write_flooding(sp)) { kvm_mmu_prepare_zap_page(vcpu->kvm, sp, &invalid_list); ++vcpu->kvm->stat.mmu_flooded; continue; } spte = get_written_sptes(sp, gpa, &npte); if (!spte) continue; while (npte--) { entry = *spte; mmu_page_zap_pte(vcpu->kvm, sp, spte, NULL); if (gentry && sp->role.level != PG_LEVEL_4K) ++vcpu->kvm->stat.mmu_pde_zapped; if (is_shadow_present_pte(entry)) flush = true; ++spte; } } kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, flush); write_unlock(&vcpu->kvm->mmu_lock); } static bool is_write_to_guest_page_table(u64 error_code) { const u64 mask = PFERR_GUEST_PAGE_MASK | PFERR_WRITE_MASK | PFERR_PRESENT_MASK; return (error_code & mask) == mask; } static int kvm_mmu_write_protect_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code, int *emulation_type) { bool direct = vcpu->arch.mmu->root_role.direct; /* * Do not try to unprotect and retry if the vCPU re-faulted on the same * RIP with the same address that was previously unprotected, as doing * so will likely put the vCPU into an infinite. E.g. if the vCPU uses * a non-page-table modifying instruction on the PDE that points to the * instruction, then unprotecting the gfn will unmap the instruction's * code, i.e. make it impossible for the instruction to ever complete. */ if (vcpu->arch.last_retry_eip == kvm_rip_read(vcpu) && vcpu->arch.last_retry_addr == cr2_or_gpa) return RET_PF_EMULATE; /* * Reset the unprotect+retry values that guard against infinite loops. * The values will be refreshed if KVM explicitly unprotects a gfn and * retries, in all other cases it's safe to retry in the future even if * the next page fault happens on the same RIP+address. */ vcpu->arch.last_retry_eip = 0; vcpu->arch.last_retry_addr = 0; /* * It should be impossible to reach this point with an MMIO cache hit, * as RET_PF_WRITE_PROTECTED is returned if and only if there's a valid, * writable memslot, and creating a memslot should invalidate the MMIO * cache by way of changing the memslot generation. WARN and disallow * retry if MMIO is detected, as retrying MMIO emulation is pointless * and could put the vCPU into an infinite loop because the processor * will keep faulting on the non-existent MMIO address. */ if (WARN_ON_ONCE(mmio_info_in_cache(vcpu, cr2_or_gpa, direct))) return RET_PF_EMULATE; /* * Before emulating the instruction, check to see if the access was due * to a read-only violation while the CPU was walking non-nested NPT * page tables, i.e. for a direct MMU, for _guest_ page tables in L1. * If L1 is sharing (a subset of) its page tables with L2, e.g. by * having nCR3 share lower level page tables with hCR3, then when KVM * (L0) write-protects the nested NPTs, i.e. npt12 entries, KVM is also * unknowingly write-protecting L1's guest page tables, which KVM isn't * shadowing. * * Because the CPU (by default) walks NPT page tables using a write * access (to ensure the CPU can do A/D updates), page walks in L1 can * trigger write faults for the above case even when L1 isn't modifying * PTEs. As a result, KVM will unnecessarily emulate (or at least, try * to emulate) an excessive number of L1 instructions; because L1's MMU * isn't shadowed by KVM, there is no need to write-protect L1's gPTEs * and thus no need to emulate in order to guarantee forward progress. * * Try to unprotect the gfn, i.e. zap any shadow pages, so that L1 can * proceed without triggering emulation. If one or more shadow pages * was zapped, skip emulation and resume L1 to let it natively execute * the instruction. If no shadow pages were zapped, then the write- * fault is due to something else entirely, i.e. KVM needs to emulate, * as resuming the guest will put it into an infinite loop. * * Note, this code also applies to Intel CPUs, even though it is *very* * unlikely that an L1 will share its page tables (IA32/PAE/paging64 * format) with L2's page tables (EPT format). * * For indirect MMUs, i.e. if KVM is shadowing the current MMU, try to * unprotect the gfn and retry if an event is awaiting reinjection. If * KVM emulates multiple instructions before completing event injection, * the event could be delayed beyond what is architecturally allowed, * e.g. KVM could inject an IRQ after the TPR has been raised. */ if (((direct && is_write_to_guest_page_table(error_code)) || (!direct && kvm_event_needs_reinjection(vcpu))) && kvm_mmu_unprotect_gfn_and_retry(vcpu, cr2_or_gpa)) return RET_PF_RETRY; /* * The gfn is write-protected, but if KVM detects its emulating an * instruction that is unlikely to be used to modify page tables, or if * emulation fails, KVM can try to unprotect the gfn and let the CPU * re-execute the instruction that caused the page fault. Do not allow * retrying an instruction from a nested guest as KVM is only explicitly * shadowing L1's page tables, i.e. unprotecting something for L1 isn't * going to magically fix whatever issue caused L2 to fail. */ if (!is_guest_mode(vcpu)) *emulation_type |= EMULTYPE_ALLOW_RETRY_PF; return RET_PF_EMULATE; } int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code, void *insn, int insn_len) { int r, emulation_type = EMULTYPE_PF; bool direct = vcpu->arch.mmu->root_role.direct; if (WARN_ON_ONCE(!VALID_PAGE(vcpu->arch.mmu->root.hpa))) return RET_PF_RETRY; /* * Except for reserved faults (emulated MMIO is shared-only), set the * PFERR_PRIVATE_ACCESS flag for software-protected VMs based on the gfn's * current attributes, which are the source of truth for such VMs. Note, * this wrong for nested MMUs as the GPA is an L2 GPA, but KVM doesn't * currently supported nested virtualization (among many other things) * for software-protected VMs. */ if (IS_ENABLED(CONFIG_KVM_SW_PROTECTED_VM) && !(error_code & PFERR_RSVD_MASK) && vcpu->kvm->arch.vm_type == KVM_X86_SW_PROTECTED_VM && kvm_mem_is_private(vcpu->kvm, gpa_to_gfn(cr2_or_gpa))) error_code |= PFERR_PRIVATE_ACCESS; r = RET_PF_INVALID; if (unlikely(error_code & PFERR_RSVD_MASK)) { if (WARN_ON_ONCE(error_code & PFERR_PRIVATE_ACCESS)) return -EFAULT; r = handle_mmio_page_fault(vcpu, cr2_or_gpa, direct); if (r == RET_PF_EMULATE) goto emulate; } if (r == RET_PF_INVALID) { vcpu->stat.pf_taken++; r = kvm_mmu_do_page_fault(vcpu, cr2_or_gpa, error_code, false, &emulation_type, NULL); if (KVM_BUG_ON(r == RET_PF_INVALID, vcpu->kvm)) return -EIO; } if (r < 0) return r; if (r == RET_PF_WRITE_PROTECTED) r = kvm_mmu_write_protect_fault(vcpu, cr2_or_gpa, error_code, &emulation_type); if (r == RET_PF_FIXED) vcpu->stat.pf_fixed++; else if (r == RET_PF_EMULATE) vcpu->stat.pf_emulate++; else if (r == RET_PF_SPURIOUS) vcpu->stat.pf_spurious++; if (r != RET_PF_EMULATE) return 1; emulate: return x86_emulate_instruction(vcpu, cr2_or_gpa, emulation_type, insn, insn_len); } EXPORT_SYMBOL_GPL(kvm_mmu_page_fault); void kvm_mmu_print_sptes(struct kvm_vcpu *vcpu, gpa_t gpa, const char *msg) { u64 sptes[PT64_ROOT_MAX_LEVEL + 1]; int root_level, leaf, level; leaf = get_sptes_lockless(vcpu, gpa, sptes, &root_level); if (unlikely(leaf < 0)) return; pr_err("%s %llx", msg, gpa); for (level = root_level; level >= leaf; level--) pr_cont(", spte[%d] = 0x%llx", level, sptes[level]); pr_cont("\n"); } EXPORT_SYMBOL_GPL(kvm_mmu_print_sptes); static void __kvm_mmu_invalidate_addr(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, u64 addr, hpa_t root_hpa) { struct kvm_shadow_walk_iterator iterator; vcpu_clear_mmio_info(vcpu, addr); /* * Walking and synchronizing SPTEs both assume they are operating in * the context of the current MMU, and would need to be reworked if * this is ever used to sync the guest_mmu, e.g. to emulate INVEPT. */ if (WARN_ON_ONCE(mmu != vcpu->arch.mmu)) return; if (!VALID_PAGE(root_hpa)) return; write_lock(&vcpu->kvm->mmu_lock); for_each_shadow_entry_using_root(vcpu, root_hpa, addr, iterator) { struct kvm_mmu_page *sp = sptep_to_sp(iterator.sptep); if (sp->unsync) { int ret = kvm_sync_spte(vcpu, sp, iterator.index); if (ret < 0) mmu_page_zap_pte(vcpu->kvm, sp, iterator.sptep, NULL); if (ret) kvm_flush_remote_tlbs_sptep(vcpu->kvm, iterator.sptep); } if (!sp->unsync_children) break; } write_unlock(&vcpu->kvm->mmu_lock); } void kvm_mmu_invalidate_addr(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, u64 addr, unsigned long roots) { int i; WARN_ON_ONCE(roots & ~KVM_MMU_ROOTS_ALL); /* It's actually a GPA for vcpu->arch.guest_mmu. */ if (mmu != &vcpu->arch.guest_mmu) { /* INVLPG on a non-canonical address is a NOP according to the SDM. */ if (is_noncanonical_invlpg_address(addr, vcpu)) return; kvm_x86_call(flush_tlb_gva)(vcpu, addr); } if (!mmu->sync_spte) return; if (roots & KVM_MMU_ROOT_CURRENT) __kvm_mmu_invalidate_addr(vcpu, mmu, addr, mmu->root.hpa); for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) { if (roots & KVM_MMU_ROOT_PREVIOUS(i)) __kvm_mmu_invalidate_addr(vcpu, mmu, addr, mmu->prev_roots[i].hpa); } } EXPORT_SYMBOL_GPL(kvm_mmu_invalidate_addr); void kvm_mmu_invlpg(struct kvm_vcpu *vcpu, gva_t gva) { /* * INVLPG is required to invalidate any global mappings for the VA, * irrespective of PCID. Blindly sync all roots as it would take * roughly the same amount of work/time to determine whether any of the * previous roots have a global mapping. * * Mappings not reachable via the current or previous cached roots will * be synced when switching to that new cr3, so nothing needs to be * done here for them. */ kvm_mmu_invalidate_addr(vcpu, vcpu->arch.walk_mmu, gva, KVM_MMU_ROOTS_ALL); ++vcpu->stat.invlpg; } EXPORT_SYMBOL_GPL(kvm_mmu_invlpg); void kvm_mmu_invpcid_gva(struct kvm_vcpu *vcpu, gva_t gva, unsigned long pcid) { struct kvm_mmu *mmu = vcpu->arch.mmu; unsigned long roots = 0; uint i; if (pcid == kvm_get_active_pcid(vcpu)) roots |= KVM_MMU_ROOT_CURRENT; for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) { if (VALID_PAGE(mmu->prev_roots[i].hpa) && pcid == kvm_get_pcid(vcpu, mmu->prev_roots[i].pgd)) roots |= KVM_MMU_ROOT_PREVIOUS(i); } if (roots) kvm_mmu_invalidate_addr(vcpu, mmu, gva, roots); ++vcpu->stat.invlpg; /* * Mappings not reachable via the current cr3 or the prev_roots will be * synced when switching to that cr3, so nothing needs to be done here * for them. */ } void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level, int tdp_max_root_level, int tdp_huge_page_level) { tdp_enabled = enable_tdp; tdp_root_level = tdp_forced_root_level; max_tdp_level = tdp_max_root_level; #ifdef CONFIG_X86_64 tdp_mmu_enabled = tdp_mmu_allowed && tdp_enabled; #endif /* * max_huge_page_level reflects KVM's MMU capabilities irrespective * of kernel support, e.g. KVM may be capable of using 1GB pages when * the kernel is not. But, KVM never creates a page size greater than * what is used by the kernel for any given HVA, i.e. the kernel's * capabilities are ultimately consulted by kvm_mmu_hugepage_adjust(). */ if (tdp_enabled) max_huge_page_level = tdp_huge_page_level; else if (boot_cpu_has(X86_FEATURE_GBPAGES)) max_huge_page_level = PG_LEVEL_1G; else max_huge_page_level = PG_LEVEL_2M; } EXPORT_SYMBOL_GPL(kvm_configure_mmu); static void free_mmu_pages(struct kvm_mmu *mmu) { if (!tdp_enabled && mmu->pae_root) set_memory_encrypted((unsigned long)mmu->pae_root, 1); free_page((unsigned long)mmu->pae_root); free_page((unsigned long)mmu->pml4_root); free_page((unsigned long)mmu->pml5_root); } static int __kvm_mmu_create(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu) { struct page *page; int i; mmu->root.hpa = INVALID_PAGE; mmu->root.pgd = 0; for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) mmu->prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID; /* vcpu->arch.guest_mmu isn't used when !tdp_enabled. */ if (!tdp_enabled && mmu == &vcpu->arch.guest_mmu) return 0; /* * When using PAE paging, the four PDPTEs are treated as 'root' pages, * while the PDP table is a per-vCPU construct that's allocated at MMU * creation. When emulating 32-bit mode, cr3 is only 32 bits even on * x86_64. Therefore we need to allocate the PDP table in the first * 4GB of memory, which happens to fit the DMA32 zone. TDP paging * generally doesn't use PAE paging and can skip allocating the PDP * table. The main exception, handled here, is SVM's 32-bit NPT. The * other exception is for shadowing L1's 32-bit or PAE NPT on 64-bit * KVM; that horror is handled on-demand by mmu_alloc_special_roots(). */ if (tdp_enabled && kvm_mmu_get_tdp_level(vcpu) > PT32E_ROOT_LEVEL) return 0; page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_DMA32); if (!page) return -ENOMEM; mmu->pae_root = page_address(page); /* * CR3 is only 32 bits when PAE paging is used, thus it's impossible to * get the CPU to treat the PDPTEs as encrypted. Decrypt the page so * that KVM's writes and the CPU's reads get along. Note, this is * only necessary when using shadow paging, as 64-bit NPT can get at * the C-bit even when shadowing 32-bit NPT, and SME isn't supported * by 32-bit kernels (when KVM itself uses 32-bit NPT). */ if (!tdp_enabled) set_memory_decrypted((unsigned long)mmu->pae_root, 1); else WARN_ON_ONCE(shadow_me_value); for (i = 0; i < 4; ++i) mmu->pae_root[i] = INVALID_PAE_ROOT; return 0; } int kvm_mmu_create(struct kvm_vcpu *vcpu) { int ret; vcpu->arch.mmu_pte_list_desc_cache.kmem_cache = pte_list_desc_cache; vcpu->arch.mmu_pte_list_desc_cache.gfp_zero = __GFP_ZERO; vcpu->arch.mmu_page_header_cache.kmem_cache = mmu_page_header_cache; vcpu->arch.mmu_page_header_cache.gfp_zero = __GFP_ZERO; vcpu->arch.mmu_shadow_page_cache.init_value = SHADOW_NONPRESENT_VALUE; if (!vcpu->arch.mmu_shadow_page_cache.init_value) vcpu->arch.mmu_shadow_page_cache.gfp_zero = __GFP_ZERO; vcpu->arch.mmu = &vcpu->arch.root_mmu; vcpu->arch.walk_mmu = &vcpu->arch.root_mmu; ret = __kvm_mmu_create(vcpu, &vcpu->arch.guest_mmu); if (ret) return ret; ret = __kvm_mmu_create(vcpu, &vcpu->arch.root_mmu); if (ret) goto fail_allocate_root; return ret; fail_allocate_root: free_mmu_pages(&vcpu->arch.guest_mmu); return ret; } #define BATCH_ZAP_PAGES 10 static void kvm_zap_obsolete_pages(struct kvm *kvm) { struct kvm_mmu_page *sp, *node; int nr_zapped, batch = 0; LIST_HEAD(invalid_list); bool unstable; lockdep_assert_held(&kvm->slots_lock); restart: list_for_each_entry_safe_reverse(sp, node, &kvm->arch.active_mmu_pages, link) { /* * No obsolete valid page exists before a newly created page * since active_mmu_pages is a FIFO list. */ if (!is_obsolete_sp(kvm, sp)) break; /* * Invalid pages should never land back on the list of active * pages. Skip the bogus page, otherwise we'll get stuck in an * infinite loop if the page gets put back on the list (again). */ if (WARN_ON_ONCE(sp->role.invalid)) continue; /* * No need to flush the TLB since we're only zapping shadow * pages with an obsolete generation number and all vCPUS have * loaded a new root, i.e. the shadow pages being zapped cannot * be in active use by the guest. */ if (batch >= BATCH_ZAP_PAGES && cond_resched_rwlock_write(&kvm->mmu_lock)) { batch = 0; goto restart; } unstable = __kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list, &nr_zapped); batch += nr_zapped; if (unstable) goto restart; } /* * Kick all vCPUs (via remote TLB flush) before freeing the page tables * to ensure KVM is not in the middle of a lockless shadow page table * walk, which may reference the pages. The remote TLB flush itself is * not required and is simply a convenient way to kick vCPUs as needed. * KVM performs a local TLB flush when allocating a new root (see * kvm_mmu_load()), and the reload in the caller ensure no vCPUs are * running with an obsolete MMU. */ kvm_mmu_commit_zap_page(kvm, &invalid_list); } /* * Fast invalidate all shadow pages and use lock-break technique * to zap obsolete pages. * * It's required when memslot is being deleted or VM is being * destroyed, in these cases, we should ensure that KVM MMU does * not use any resource of the being-deleted slot or all slots * after calling the function. */ static void kvm_mmu_zap_all_fast(struct kvm *kvm) { lockdep_assert_held(&kvm->slots_lock); write_lock(&kvm->mmu_lock); trace_kvm_mmu_zap_all_fast(kvm); /* * Toggle mmu_valid_gen between '0' and '1'. Because slots_lock is * held for the entire duration of zapping obsolete pages, it's * impossible for there to be multiple invalid generations associated * with *valid* shadow pages at any given time, i.e. there is exactly * one valid generation and (at most) one invalid generation. */ kvm->arch.mmu_valid_gen = kvm->arch.mmu_valid_gen ? 0 : 1; /* * In order to ensure all vCPUs drop their soon-to-be invalid roots, * invalidating TDP MMU roots must be done while holding mmu_lock for * write and in the same critical section as making the reload request, * e.g. before kvm_zap_obsolete_pages() could drop mmu_lock and yield. */ if (tdp_mmu_enabled) kvm_tdp_mmu_invalidate_all_roots(kvm); /* * Notify all vcpus to reload its shadow page table and flush TLB. * Then all vcpus will switch to new shadow page table with the new * mmu_valid_gen. * * Note: we need to do this under the protection of mmu_lock, * otherwise, vcpu would purge shadow page but miss tlb flush. */ kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_FREE_OBSOLETE_ROOTS); kvm_zap_obsolete_pages(kvm); write_unlock(&kvm->mmu_lock); /* * Zap the invalidated TDP MMU roots, all SPTEs must be dropped before * returning to the caller, e.g. if the zap is in response to a memslot * deletion, mmu_notifier callbacks will be unable to reach the SPTEs * associated with the deleted memslot once the update completes, and * Deferring the zap until the final reference to the root is put would * lead to use-after-free. */ if (tdp_mmu_enabled) kvm_tdp_mmu_zap_invalidated_roots(kvm); } void kvm_mmu_init_vm(struct kvm *kvm) { kvm->arch.shadow_mmio_value = shadow_mmio_value; INIT_LIST_HEAD(&kvm->arch.active_mmu_pages); INIT_LIST_HEAD(&kvm->arch.possible_nx_huge_pages); spin_lock_init(&kvm->arch.mmu_unsync_pages_lock); if (tdp_mmu_enabled) kvm_mmu_init_tdp_mmu(kvm); kvm->arch.split_page_header_cache.kmem_cache = mmu_page_header_cache; kvm->arch.split_page_header_cache.gfp_zero = __GFP_ZERO; kvm->arch.split_shadow_page_cache.gfp_zero = __GFP_ZERO; kvm->arch.split_desc_cache.kmem_cache = pte_list_desc_cache; kvm->arch.split_desc_cache.gfp_zero = __GFP_ZERO; } static void mmu_free_vm_memory_caches(struct kvm *kvm) { kvm_mmu_free_memory_cache(&kvm->arch.split_desc_cache); kvm_mmu_free_memory_cache(&kvm->arch.split_page_header_cache); kvm_mmu_free_memory_cache(&kvm->arch.split_shadow_page_cache); } void kvm_mmu_uninit_vm(struct kvm *kvm) { if (tdp_mmu_enabled) kvm_mmu_uninit_tdp_mmu(kvm); mmu_free_vm_memory_caches(kvm); } static bool kvm_rmap_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end) { const struct kvm_memory_slot *memslot; struct kvm_memslots *slots; struct kvm_memslot_iter iter; bool flush = false; gfn_t start, end; int i; if (!kvm_memslots_have_rmaps(kvm)) return flush; for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) { slots = __kvm_memslots(kvm, i); kvm_for_each_memslot_in_gfn_range(&iter, slots, gfn_start, gfn_end) { memslot = iter.slot; start = max(gfn_start, memslot->base_gfn); end = min(gfn_end, memslot->base_gfn + memslot->npages); if (WARN_ON_ONCE(start >= end)) continue; flush = __kvm_rmap_zap_gfn_range(kvm, memslot, start, end, true, flush); } } return flush; } /* * Invalidate (zap) SPTEs that cover GFNs from gfn_start and up to gfn_end * (not including it) */ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end) { bool flush; if (WARN_ON_ONCE(gfn_end <= gfn_start)) return; write_lock(&kvm->mmu_lock); kvm_mmu_invalidate_begin(kvm); kvm_mmu_invalidate_range_add(kvm, gfn_start, gfn_end); flush = kvm_rmap_zap_gfn_range(kvm, gfn_start, gfn_end); if (tdp_mmu_enabled) flush = kvm_tdp_mmu_zap_leafs(kvm, gfn_start, gfn_end, flush); if (flush) kvm_flush_remote_tlbs_range(kvm, gfn_start, gfn_end - gfn_start); kvm_mmu_invalidate_end(kvm); write_unlock(&kvm->mmu_lock); } static bool slot_rmap_write_protect(struct kvm *kvm, struct kvm_rmap_head *rmap_head, const struct kvm_memory_slot *slot) { return rmap_write_protect(rmap_head, false); } void kvm_mmu_slot_remove_write_access(struct kvm *kvm, const struct kvm_memory_slot *memslot, int start_level) { if (kvm_memslots_have_rmaps(kvm)) { write_lock(&kvm->mmu_lock); walk_slot_rmaps(kvm, memslot, slot_rmap_write_protect, start_level, KVM_MAX_HUGEPAGE_LEVEL, false); write_unlock(&kvm->mmu_lock); } if (tdp_mmu_enabled) { read_lock(&kvm->mmu_lock); kvm_tdp_mmu_wrprot_slot(kvm, memslot, start_level); read_unlock(&kvm->mmu_lock); } } static inline bool need_topup(struct kvm_mmu_memory_cache *cache, int min) { return kvm_mmu_memory_cache_nr_free_objects(cache) < min; } static bool need_topup_split_caches_or_resched(struct kvm *kvm) { if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) return true; /* * In the worst case, SPLIT_DESC_CACHE_MIN_NR_OBJECTS descriptors are needed * to split a single huge page. Calculating how many are actually needed * is possible but not worth the complexity. */ return need_topup(&kvm->arch.split_desc_cache, SPLIT_DESC_CACHE_MIN_NR_OBJECTS) || need_topup(&kvm->arch.split_page_header_cache, 1) || need_topup(&kvm->arch.split_shadow_page_cache, 1); } static int topup_split_caches(struct kvm *kvm) { /* * Allocating rmap list entries when splitting huge pages for nested * MMUs is uncommon as KVM needs to use a list if and only if there is * more than one rmap entry for a gfn, i.e. requires an L1 gfn to be * aliased by multiple L2 gfns and/or from multiple nested roots with * different roles. Aliasing gfns when using TDP is atypical for VMMs; * a few gfns are often aliased during boot, e.g. when remapping BIOS, * but aliasing rarely occurs post-boot or for many gfns. If there is * only one rmap entry, rmap->val points directly at that one entry and * doesn't need to allocate a list. Buffer the cache by the default * capacity so that KVM doesn't have to drop mmu_lock to topup if KVM * encounters an aliased gfn or two. */ const int capacity = SPLIT_DESC_CACHE_MIN_NR_OBJECTS + KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE; int r; lockdep_assert_held(&kvm->slots_lock); r = __kvm_mmu_topup_memory_cache(&kvm->arch.split_desc_cache, capacity, SPLIT_DESC_CACHE_MIN_NR_OBJECTS); if (r) return r; r = kvm_mmu_topup_memory_cache(&kvm->arch.split_page_header_cache, 1); if (r) return r; return kvm_mmu_topup_memory_cache(&kvm->arch.split_shadow_page_cache, 1); } static struct kvm_mmu_page *shadow_mmu_get_sp_for_split(struct kvm *kvm, u64 *huge_sptep) { struct kvm_mmu_page *huge_sp = sptep_to_sp(huge_sptep); struct shadow_page_caches caches = {}; union kvm_mmu_page_role role; unsigned int access; gfn_t gfn; gfn = kvm_mmu_page_get_gfn(huge_sp, spte_index(huge_sptep)); access = kvm_mmu_page_get_access(huge_sp, spte_index(huge_sptep)); /* * Note, huge page splitting always uses direct shadow pages, regardless * of whether the huge page itself is mapped by a direct or indirect * shadow page, since the huge page region itself is being directly * mapped with smaller pages. */ role = kvm_mmu_child_role(huge_sptep, /*direct=*/true, access); /* Direct SPs do not require a shadowed_info_cache. */ caches.page_header_cache = &kvm->arch.split_page_header_cache; caches.shadow_page_cache = &kvm->arch.split_shadow_page_cache; /* Safe to pass NULL for vCPU since requesting a direct SP. */ return __kvm_mmu_get_shadow_page(kvm, NULL, &caches, gfn, role); } static void shadow_mmu_split_huge_page(struct kvm *kvm, const struct kvm_memory_slot *slot, u64 *huge_sptep) { struct kvm_mmu_memory_cache *cache = &kvm->arch.split_desc_cache; u64 huge_spte = READ_ONCE(*huge_sptep); struct kvm_mmu_page *sp; bool flush = false; u64 *sptep, spte; gfn_t gfn; int index; sp = shadow_mmu_get_sp_for_split(kvm, huge_sptep); for (index = 0; index < SPTE_ENT_PER_PAGE; index++) { sptep = &sp->spt[index]; gfn = kvm_mmu_page_get_gfn(sp, index); /* * The SP may already have populated SPTEs, e.g. if this huge * page is aliased by multiple sptes with the same access * permissions. These entries are guaranteed to map the same * gfn-to-pfn translation since the SP is direct, so no need to * modify them. * * However, if a given SPTE points to a lower level page table, * that lower level page table may only be partially populated. * Installing such SPTEs would effectively unmap a potion of the * huge page. Unmapping guest memory always requires a TLB flush * since a subsequent operation on the unmapped regions would * fail to detect the need to flush. */ if (is_shadow_present_pte(*sptep)) { flush |= !is_last_spte(*sptep, sp->role.level); continue; } spte = make_small_spte(kvm, huge_spte, sp->role, index); mmu_spte_set(sptep, spte); __rmap_add(kvm, cache, slot, sptep, gfn, sp->role.access); } __link_shadow_page(kvm, cache, huge_sptep, sp, flush); } static int shadow_mmu_try_split_huge_page(struct kvm *kvm, const struct kvm_memory_slot *slot, u64 *huge_sptep) { struct kvm_mmu_page *huge_sp = sptep_to_sp(huge_sptep); int level, r = 0; gfn_t gfn; u64 spte; /* Grab information for the tracepoint before dropping the MMU lock. */ gfn = kvm_mmu_page_get_gfn(huge_sp, spte_index(huge_sptep)); level = huge_sp->role.level; spte = *huge_sptep; if (kvm_mmu_available_pages(kvm) <= KVM_MIN_FREE_MMU_PAGES) { r = -ENOSPC; goto out; } if (need_topup_split_caches_or_resched(kvm)) { write_unlock(&kvm->mmu_lock); cond_resched(); /* * If the topup succeeds, return -EAGAIN to indicate that the * rmap iterator should be restarted because the MMU lock was * dropped. */ r = topup_split_caches(kvm) ?: -EAGAIN; write_lock(&kvm->mmu_lock); goto out; } shadow_mmu_split_huge_page(kvm, slot, huge_sptep); out: trace_kvm_mmu_split_huge_page(gfn, spte, level, r); return r; } static bool shadow_mmu_try_split_huge_pages(struct kvm *kvm, struct kvm_rmap_head *rmap_head, const struct kvm_memory_slot *slot) { struct rmap_iterator iter; struct kvm_mmu_page *sp; u64 *huge_sptep; int r; restart: for_each_rmap_spte(rmap_head, &iter, huge_sptep) { sp = sptep_to_sp(huge_sptep); /* TDP MMU is enabled, so rmap only contains nested MMU SPs. */ if (WARN_ON_ONCE(!sp->role.guest_mode)) continue; /* The rmaps should never contain non-leaf SPTEs. */ if (WARN_ON_ONCE(!is_large_pte(*huge_sptep))) continue; /* SPs with level >PG_LEVEL_4K should never by unsync. */ if (WARN_ON_ONCE(sp->unsync)) continue; /* Don't bother splitting huge pages on invalid SPs. */ if (sp->role.invalid) continue; r = shadow_mmu_try_split_huge_page(kvm, slot, huge_sptep); /* * The split succeeded or needs to be retried because the MMU * lock was dropped. Either way, restart the iterator to get it * back into a consistent state. */ if (!r || r == -EAGAIN) goto restart; /* The split failed and shouldn't be retried (e.g. -ENOMEM). */ break; } return false; } static void kvm_shadow_mmu_try_split_huge_pages(struct kvm *kvm, const struct kvm_memory_slot *slot, gfn_t start, gfn_t end, int target_level) { int level; /* * Split huge pages starting with KVM_MAX_HUGEPAGE_LEVEL and working * down to the target level. This ensures pages are recursively split * all the way to the target level. There's no need to split pages * already at the target level. */ for (level = KVM_MAX_HUGEPAGE_LEVEL; level > target_level; level--) __walk_slot_rmaps(kvm, slot, shadow_mmu_try_split_huge_pages, level, level, start, end - 1, true, true, false); } /* Must be called with the mmu_lock held in write-mode. */ void kvm_mmu_try_split_huge_pages(struct kvm *kvm, const struct kvm_memory_slot *memslot, u64 start, u64 end, int target_level) { if (!tdp_mmu_enabled) return; if (kvm_memslots_have_rmaps(kvm)) kvm_shadow_mmu_try_split_huge_pages(kvm, memslot, start, end, target_level); kvm_tdp_mmu_try_split_huge_pages(kvm, memslot, start, end, target_level, false); /* * A TLB flush is unnecessary at this point for the same reasons as in * kvm_mmu_slot_try_split_huge_pages(). */ } void kvm_mmu_slot_try_split_huge_pages(struct kvm *kvm, const struct kvm_memory_slot *memslot, int target_level) { u64 start = memslot->base_gfn; u64 end = start + memslot->npages; if (!tdp_mmu_enabled) return; if (kvm_memslots_have_rmaps(kvm)) { write_lock(&kvm->mmu_lock); kvm_shadow_mmu_try_split_huge_pages(kvm, memslot, start, end, target_level); write_unlock(&kvm->mmu_lock); } read_lock(&kvm->mmu_lock); kvm_tdp_mmu_try_split_huge_pages(kvm, memslot, start, end, target_level, true); read_unlock(&kvm->mmu_lock); /* * No TLB flush is necessary here. KVM will flush TLBs after * write-protecting and/or clearing dirty on the newly split SPTEs to * ensure that guest writes are reflected in the dirty log before the * ioctl to enable dirty logging on this memslot completes. Since the * split SPTEs retain the write and dirty bits of the huge SPTE, it is * safe for KVM to decide if a TLB flush is necessary based on the split * SPTEs. */ } static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm, struct kvm_rmap_head *rmap_head, const struct kvm_memory_slot *slot) { u64 *sptep; struct rmap_iterator iter; int need_tlb_flush = 0; struct kvm_mmu_page *sp; restart: for_each_rmap_spte(rmap_head, &iter, sptep) { sp = sptep_to_sp(sptep); /* * We cannot do huge page mapping for indirect shadow pages, * which are found on the last rmap (level = 1) when not using * tdp; such shadow pages are synced with the page table in * the guest, and the guest page table is using 4K page size * mapping if the indirect sp has level = 1. */ if (sp->role.direct && sp->role.level < kvm_mmu_max_mapping_level(kvm, slot, sp->gfn)) { kvm_zap_one_rmap_spte(kvm, rmap_head, sptep); if (kvm_available_flush_remote_tlbs_range()) kvm_flush_remote_tlbs_sptep(kvm, sptep); else need_tlb_flush = 1; goto restart; } } return need_tlb_flush; } EXPORT_SYMBOL_GPL(kvm_zap_gfn_range); static void kvm_rmap_zap_collapsible_sptes(struct kvm *kvm, const struct kvm_memory_slot *slot) { /* * Note, use KVM_MAX_HUGEPAGE_LEVEL - 1 since there's no need to zap * pages that are already mapped at the maximum hugepage level. */ if (walk_slot_rmaps(kvm, slot, kvm_mmu_zap_collapsible_spte, PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL - 1, true)) kvm_flush_remote_tlbs_memslot(kvm, slot); } void kvm_mmu_recover_huge_pages(struct kvm *kvm, const struct kvm_memory_slot *slot) { if (kvm_memslots_have_rmaps(kvm)) { write_lock(&kvm->mmu_lock); kvm_rmap_zap_collapsible_sptes(kvm, slot); write_unlock(&kvm->mmu_lock); } if (tdp_mmu_enabled) { read_lock(&kvm->mmu_lock); kvm_tdp_mmu_recover_huge_pages(kvm, slot); read_unlock(&kvm->mmu_lock); } } void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm, const struct kvm_memory_slot *memslot) { if (kvm_memslots_have_rmaps(kvm)) { write_lock(&kvm->mmu_lock); /* * Clear dirty bits only on 4k SPTEs since the legacy MMU only * support dirty logging at a 4k granularity. */ walk_slot_rmaps_4k(kvm, memslot, __rmap_clear_dirty, false); write_unlock(&kvm->mmu_lock); } if (tdp_mmu_enabled) { read_lock(&kvm->mmu_lock); kvm_tdp_mmu_clear_dirty_slot(kvm, memslot); read_unlock(&kvm->mmu_lock); } /* * The caller will flush the TLBs after this function returns. * * It's also safe to flush TLBs out of mmu lock here as currently this * function is only used for dirty logging, in which case flushing TLB * out of mmu lock also guarantees no dirty pages will be lost in * dirty_bitmap. */ } static void kvm_mmu_zap_all(struct kvm *kvm) { struct kvm_mmu_page *sp, *node; LIST_HEAD(invalid_list); int ign; write_lock(&kvm->mmu_lock); restart: list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) { if (WARN_ON_ONCE(sp->role.invalid)) continue; if (__kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list, &ign)) goto restart; if (cond_resched_rwlock_write(&kvm->mmu_lock)) goto restart; } kvm_mmu_commit_zap_page(kvm, &invalid_list); if (tdp_mmu_enabled) kvm_tdp_mmu_zap_all(kvm); write_unlock(&kvm->mmu_lock); } void kvm_arch_flush_shadow_all(struct kvm *kvm) { kvm_mmu_zap_all(kvm); } static void kvm_mmu_zap_memslot_pages_and_flush(struct kvm *kvm, struct kvm_memory_slot *slot, bool flush) { LIST_HEAD(invalid_list); unsigned long i; if (list_empty(&kvm->arch.active_mmu_pages)) goto out_flush; /* * Since accounting information is stored in struct kvm_arch_memory_slot, * all MMU pages that are shadowing guest PTEs must be zapped before the * memslot is deleted, as freeing such pages after the memslot is freed * will result in use-after-free, e.g. in unaccount_shadowed(). */ for (i = 0; i < slot->npages; i++) { struct kvm_mmu_page *sp; gfn_t gfn = slot->base_gfn + i; for_each_gfn_valid_sp_with_gptes(kvm, sp, gfn) kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list); if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) { kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush); flush = false; cond_resched_rwlock_write(&kvm->mmu_lock); } } out_flush: kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush); } static void kvm_mmu_zap_memslot(struct kvm *kvm, struct kvm_memory_slot *slot) { struct kvm_gfn_range range = { .slot = slot, .start = slot->base_gfn, .end = slot->base_gfn + slot->npages, .may_block = true, }; bool flush; write_lock(&kvm->mmu_lock); flush = kvm_unmap_gfn_range(kvm, &range); kvm_mmu_zap_memslot_pages_and_flush(kvm, slot, flush); write_unlock(&kvm->mmu_lock); } static inline bool kvm_memslot_flush_zap_all(struct kvm *kvm) { return kvm->arch.vm_type == KVM_X86_DEFAULT_VM && kvm_check_has_quirk(kvm, KVM_X86_QUIRK_SLOT_ZAP_ALL); } void kvm_arch_flush_shadow_memslot(struct kvm *kvm, struct kvm_memory_slot *slot) { if (kvm_memslot_flush_zap_all(kvm)) kvm_mmu_zap_all_fast(kvm); else kvm_mmu_zap_memslot(kvm, slot); } void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen) { WARN_ON_ONCE(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS); gen &= MMIO_SPTE_GEN_MASK; /* * Generation numbers are incremented in multiples of the number of * address spaces in order to provide unique generations across all * address spaces. Strip what is effectively the address space * modifier prior to checking for a wrap of the MMIO generation so * that a wrap in any address space is detected. */ gen &= ~((u64)kvm_arch_nr_memslot_as_ids(kvm) - 1); /* * The very rare case: if the MMIO generation number has wrapped, * zap all shadow pages. */ if (unlikely(gen == 0)) { kvm_debug_ratelimited("zapping shadow pages for mmio generation wraparound\n"); kvm_mmu_zap_all_fast(kvm); } } static void mmu_destroy_caches(void) { kmem_cache_destroy(pte_list_desc_cache); kmem_cache_destroy(mmu_page_header_cache); } static int get_nx_huge_pages(char *buffer, const struct kernel_param *kp) { if (nx_hugepage_mitigation_hard_disabled) return sysfs_emit(buffer, "never\n"); return param_get_bool(buffer, kp); } static bool get_nx_auto_mode(void) { /* Return true when CPU has the bug, and mitigations are ON */ return boot_cpu_has_bug(X86_BUG_ITLB_MULTIHIT) && !cpu_mitigations_off(); } static void __set_nx_huge_pages(bool val) { nx_huge_pages = itlb_multihit_kvm_mitigation = val; } static int set_nx_huge_pages(const char *val, const struct kernel_param *kp) { bool old_val = nx_huge_pages; bool new_val; if (nx_hugepage_mitigation_hard_disabled) return -EPERM; /* In "auto" mode deploy workaround only if CPU has the bug. */ if (sysfs_streq(val, "off")) { new_val = 0; } else if (sysfs_streq(val, "force")) { new_val = 1; } else if (sysfs_streq(val, "auto")) { new_val = get_nx_auto_mode(); } else if (sysfs_streq(val, "never")) { new_val = 0; mutex_lock(&kvm_lock); if (!list_empty(&vm_list)) { mutex_unlock(&kvm_lock); return -EBUSY; } nx_hugepage_mitigation_hard_disabled = true; mutex_unlock(&kvm_lock); } else if (kstrtobool(val, &new_val) < 0) { return -EINVAL; } __set_nx_huge_pages(new_val); if (new_val != old_val) { struct kvm *kvm; mutex_lock(&kvm_lock); list_for_each_entry(kvm, &vm_list, vm_list) { mutex_lock(&kvm->slots_lock); kvm_mmu_zap_all_fast(kvm); mutex_unlock(&kvm->slots_lock); vhost_task_wake(kvm->arch.nx_huge_page_recovery_thread); } mutex_unlock(&kvm_lock); } return 0; } /* * nx_huge_pages needs to be resolved to true/false when kvm.ko is loaded, as * its default value of -1 is technically undefined behavior for a boolean. * Forward the module init call to SPTE code so that it too can handle module * params that need to be resolved/snapshot. */ void __init kvm_mmu_x86_module_init(void) { if (nx_huge_pages == -1) __set_nx_huge_pages(get_nx_auto_mode()); /* * Snapshot userspace's desire to enable the TDP MMU. Whether or not the * TDP MMU is actually enabled is determined in kvm_configure_mmu() * when the vendor module is loaded. */ tdp_mmu_allowed = tdp_mmu_enabled; kvm_mmu_spte_module_init(); } /* * The bulk of the MMU initialization is deferred until the vendor module is * loaded as many of the masks/values may be modified by VMX or SVM, i.e. need * to be reset when a potentially different vendor module is loaded. */ int kvm_mmu_vendor_module_init(void) { int ret = -ENOMEM; /* * MMU roles use union aliasing which is, generally speaking, an * undefined behavior. However, we supposedly know how compilers behave * and the current status quo is unlikely to change. Guardians below are * supposed to let us know if the assumption becomes false. */ BUILD_BUG_ON(sizeof(union kvm_mmu_page_role) != sizeof(u32)); BUILD_BUG_ON(sizeof(union kvm_mmu_extended_role) != sizeof(u32)); BUILD_BUG_ON(sizeof(union kvm_cpu_role) != sizeof(u64)); kvm_mmu_reset_all_pte_masks(); pte_list_desc_cache = KMEM_CACHE(pte_list_desc, SLAB_ACCOUNT); if (!pte_list_desc_cache) goto out; mmu_page_header_cache = kmem_cache_create("kvm_mmu_page_header", sizeof(struct kvm_mmu_page), 0, SLAB_ACCOUNT, NULL); if (!mmu_page_header_cache) goto out; return 0; out: mmu_destroy_caches(); return ret; } void kvm_mmu_destroy(struct kvm_vcpu *vcpu) { kvm_mmu_unload(vcpu); free_mmu_pages(&vcpu->arch.root_mmu); free_mmu_pages(&vcpu->arch.guest_mmu); mmu_free_memory_caches(vcpu); } void kvm_mmu_vendor_module_exit(void) { mmu_destroy_caches(); } /* * Calculate the effective recovery period, accounting for '0' meaning "let KVM * select a halving time of 1 hour". Returns true if recovery is enabled. */ static bool calc_nx_huge_pages_recovery_period(uint *period) { /* * Use READ_ONCE to get the params, this may be called outside of the * param setters, e.g. by the kthread to compute its next timeout. */ bool enabled = READ_ONCE(nx_huge_pages); uint ratio = READ_ONCE(nx_huge_pages_recovery_ratio); if (!enabled || !ratio) return false; *period = READ_ONCE(nx_huge_pages_recovery_period_ms); if (!*period) { /* Make sure the period is not less than one second. */ ratio = min(ratio, 3600u); *period = 60 * 60 * 1000 / ratio; } return true; } static int set_nx_huge_pages_recovery_param(const char *val, const struct kernel_param *kp) { bool was_recovery_enabled, is_recovery_enabled; uint old_period, new_period; int err; if (nx_hugepage_mitigation_hard_disabled) return -EPERM; was_recovery_enabled = calc_nx_huge_pages_recovery_period(&old_period); err = param_set_uint(val, kp); if (err) return err; is_recovery_enabled = calc_nx_huge_pages_recovery_period(&new_period); if (is_recovery_enabled && (!was_recovery_enabled || old_period > new_period)) { struct kvm *kvm; mutex_lock(&kvm_lock); list_for_each_entry(kvm, &vm_list, vm_list) vhost_task_wake(kvm->arch.nx_huge_page_recovery_thread); mutex_unlock(&kvm_lock); } return err; } static void kvm_recover_nx_huge_pages(struct kvm *kvm) { unsigned long nx_lpage_splits = kvm->stat.nx_lpage_splits; struct kvm_memory_slot *slot; int rcu_idx; struct kvm_mmu_page *sp; unsigned int ratio; LIST_HEAD(invalid_list); bool flush = false; ulong to_zap; rcu_idx = srcu_read_lock(&kvm->srcu); write_lock(&kvm->mmu_lock); /* * Zapping TDP MMU shadow pages, including the remote TLB flush, must * be done under RCU protection, because the pages are freed via RCU * callback. */ rcu_read_lock(); ratio = READ_ONCE(nx_huge_pages_recovery_ratio); to_zap = ratio ? DIV_ROUND_UP(nx_lpage_splits, ratio) : 0; for ( ; to_zap; --to_zap) { if (list_empty(&kvm->arch.possible_nx_huge_pages)) break; /* * We use a separate list instead of just using active_mmu_pages * because the number of shadow pages that be replaced with an * NX huge page is expected to be relatively small compared to * the total number of shadow pages. And because the TDP MMU * doesn't use active_mmu_pages. */ sp = list_first_entry(&kvm->arch.possible_nx_huge_pages, struct kvm_mmu_page, possible_nx_huge_page_link); WARN_ON_ONCE(!sp->nx_huge_page_disallowed); WARN_ON_ONCE(!sp->role.direct); /* * Unaccount and do not attempt to recover any NX Huge Pages * that are being dirty tracked, as they would just be faulted * back in as 4KiB pages. The NX Huge Pages in this slot will be * recovered, along with all the other huge pages in the slot, * when dirty logging is disabled. * * Since gfn_to_memslot() is relatively expensive, it helps to * skip it if it the test cannot possibly return true. On the * other hand, if any memslot has logging enabled, chances are * good that all of them do, in which case unaccount_nx_huge_page() * is much cheaper than zapping the page. * * If a memslot update is in progress, reading an incorrect value * of kvm->nr_memslots_dirty_logging is not a problem: if it is * becoming zero, gfn_to_memslot() will be done unnecessarily; if * it is becoming nonzero, the page will be zapped unnecessarily. * Either way, this only affects efficiency in racy situations, * and not correctness. */ slot = NULL; if (atomic_read(&kvm->nr_memslots_dirty_logging)) { struct kvm_memslots *slots; slots = kvm_memslots_for_spte_role(kvm, sp->role); slot = __gfn_to_memslot(slots, sp->gfn); WARN_ON_ONCE(!slot); } if (slot && kvm_slot_dirty_track_enabled(slot)) unaccount_nx_huge_page(kvm, sp); else if (is_tdp_mmu_page(sp)) flush |= kvm_tdp_mmu_zap_sp(kvm, sp); else kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list); WARN_ON_ONCE(sp->nx_huge_page_disallowed); if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) { kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush); rcu_read_unlock(); cond_resched_rwlock_write(&kvm->mmu_lock); flush = false; rcu_read_lock(); } } kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush); rcu_read_unlock(); write_unlock(&kvm->mmu_lock); srcu_read_unlock(&kvm->srcu, rcu_idx); } static void kvm_nx_huge_page_recovery_worker_kill(void *data) { } static bool kvm_nx_huge_page_recovery_worker(void *data) { struct kvm *kvm = data; bool enabled; uint period; long remaining_time; enabled = calc_nx_huge_pages_recovery_period(&period); if (!enabled) return false; remaining_time = kvm->arch.nx_huge_page_last + msecs_to_jiffies(period) - get_jiffies_64(); if (remaining_time > 0) { schedule_timeout(remaining_time); /* check for signals and come back */ return true; } __set_current_state(TASK_RUNNING); kvm_recover_nx_huge_pages(kvm); kvm->arch.nx_huge_page_last = get_jiffies_64(); return true; } int kvm_mmu_post_init_vm(struct kvm *kvm) { if (nx_hugepage_mitigation_hard_disabled) return 0; kvm->arch.nx_huge_page_last = get_jiffies_64(); kvm->arch.nx_huge_page_recovery_thread = vhost_task_create( kvm_nx_huge_page_recovery_worker, kvm_nx_huge_page_recovery_worker_kill, kvm, "kvm-nx-lpage-recovery"); if (!kvm->arch.nx_huge_page_recovery_thread) return -ENOMEM; vhost_task_start(kvm->arch.nx_huge_page_recovery_thread); return 0; } void kvm_mmu_pre_destroy_vm(struct kvm *kvm) { if (kvm->arch.nx_huge_page_recovery_thread) vhost_task_stop(kvm->arch.nx_huge_page_recovery_thread); } #ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm, struct kvm_gfn_range *range) { /* * Zap SPTEs even if the slot can't be mapped PRIVATE. KVM x86 only * supports KVM_MEMORY_ATTRIBUTE_PRIVATE, and so it *seems* like KVM * can simply ignore such slots. But if userspace is making memory * PRIVATE, then KVM must prevent the guest from accessing the memory * as shared. And if userspace is making memory SHARED and this point * is reached, then at least one page within the range was previously * PRIVATE, i.e. the slot's possible hugepage ranges are changing. * Zapping SPTEs in this case ensures KVM will reassess whether or not * a hugepage can be used for affected ranges. */ if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm))) return false; return kvm_unmap_gfn_range(kvm, range); } static bool hugepage_test_mixed(struct kvm_memory_slot *slot, gfn_t gfn, int level) { return lpage_info_slot(gfn, slot, level)->disallow_lpage & KVM_LPAGE_MIXED_FLAG; } static void hugepage_clear_mixed(struct kvm_memory_slot *slot, gfn_t gfn, int level) { lpage_info_slot(gfn, slot, level)->disallow_lpage &= ~KVM_LPAGE_MIXED_FLAG; } static void hugepage_set_mixed(struct kvm_memory_slot *slot, gfn_t gfn, int level) { lpage_info_slot(gfn, slot, level)->disallow_lpage |= KVM_LPAGE_MIXED_FLAG; } static bool hugepage_has_attrs(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, int level, unsigned long attrs) { const unsigned long start = gfn; const unsigned long end = start + KVM_PAGES_PER_HPAGE(level); if (level == PG_LEVEL_2M) return kvm_range_has_memory_attributes(kvm, start, end, ~0, attrs); for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) { if (hugepage_test_mixed(slot, gfn, level - 1) || attrs != kvm_get_memory_attributes(kvm, gfn)) return false; } return true; } bool kvm_arch_post_set_memory_attributes(struct kvm *kvm, struct kvm_gfn_range *range) { unsigned long attrs = range->arg.attributes; struct kvm_memory_slot *slot = range->slot; int level; lockdep_assert_held_write(&kvm->mmu_lock); lockdep_assert_held(&kvm->slots_lock); /* * Calculate which ranges can be mapped with hugepages even if the slot * can't map memory PRIVATE. KVM mustn't create a SHARED hugepage over * a range that has PRIVATE GFNs, and conversely converting a range to * SHARED may now allow hugepages. */ if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm))) return false; /* * The sequence matters here: upper levels consume the result of lower * level's scanning. */ for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) { gfn_t nr_pages = KVM_PAGES_PER_HPAGE(level); gfn_t gfn = gfn_round_for_level(range->start, level); /* Process the head page if it straddles the range. */ if (gfn != range->start || gfn + nr_pages > range->end) { /* * Skip mixed tracking if the aligned gfn isn't covered * by the memslot, KVM can't use a hugepage due to the * misaligned address regardless of memory attributes. */ if (gfn >= slot->base_gfn && gfn + nr_pages <= slot->base_gfn + slot->npages) { if (hugepage_has_attrs(kvm, slot, gfn, level, attrs)) hugepage_clear_mixed(slot, gfn, level); else hugepage_set_mixed(slot, gfn, level); } gfn += nr_pages; } /* * Pages entirely covered by the range are guaranteed to have * only the attributes which were just set. */ for ( ; gfn + nr_pages <= range->end; gfn += nr_pages) hugepage_clear_mixed(slot, gfn, level); /* * Process the last tail page if it straddles the range and is * contained by the memslot. Like the head page, KVM can't * create a hugepage if the slot size is misaligned. */ if (gfn < range->end && (gfn + nr_pages) <= (slot->base_gfn + slot->npages)) { if (hugepage_has_attrs(kvm, slot, gfn, level, attrs)) hugepage_clear_mixed(slot, gfn, level); else hugepage_set_mixed(slot, gfn, level); } } return false; } void kvm_mmu_init_memslot_memory_attributes(struct kvm *kvm, struct kvm_memory_slot *slot) { int level; if (!kvm_arch_has_private_mem(kvm)) return; for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) { /* * Don't bother tracking mixed attributes for pages that can't * be huge due to alignment, i.e. process only pages that are * entirely contained by the memslot. */ gfn_t end = gfn_round_for_level(slot->base_gfn + slot->npages, level); gfn_t start = gfn_round_for_level(slot->base_gfn, level); gfn_t nr_pages = KVM_PAGES_PER_HPAGE(level); gfn_t gfn; if (start < slot->base_gfn) start += nr_pages; /* * Unlike setting attributes, every potential hugepage needs to * be manually checked as the attributes may already be mixed. */ for (gfn = start; gfn < end; gfn += nr_pages) { unsigned long attrs = kvm_get_memory_attributes(kvm, gfn); if (hugepage_has_attrs(kvm, slot, gfn, level, attrs)) hugepage_clear_mixed(slot, gfn, level); else hugepage_set_mixed(slot, gfn, level); } } } #endif
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