| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Dave P Martin | 3030 | 78.84% | 44 | 66.67% |
| Catalin Marinas | 217 | 5.65% | 2 | 3.03% |
| Julien Grall | 162 | 4.22% | 2 | 3.03% |
| Ard Biesheuvel | 144 | 3.75% | 4 | 6.06% |
| Suzuki K. Poulose | 113 | 2.94% | 4 | 6.06% |
| Lorenzo Pieralisi | 88 | 2.29% | 1 | 1.52% |
| Janet Liu | 49 | 1.28% | 1 | 1.52% |
| Will Deacon | 14 | 0.36% | 2 | 3.03% |
| Sebastian Andrzej Siewior | 11 | 0.29% | 1 | 1.52% |
| Andrew Murray | 8 | 0.21% | 1 | 1.52% |
| Eric W. Biedermann | 3 | 0.08% | 1 | 1.52% |
| Thomas Gleixner | 2 | 0.05% | 1 | 1.52% |
| Leo Yan | 1 | 0.03% | 1 | 1.52% |
| JiSheng Zhang | 1 | 0.03% | 1 | 1.52% |
| Total | 3843 | 66 |
// SPDX-License-Identifier: GPL-2.0-only /* * FP/SIMD context switching and fault handling * * Copyright (C) 2012 ARM Ltd. * Author: Catalin Marinas <catalin.marinas@arm.com> */ #include <linux/bitmap.h> #include <linux/bitops.h> #include <linux/bottom_half.h> #include <linux/bug.h> #include <linux/cache.h> #include <linux/compat.h> #include <linux/compiler.h> #include <linux/cpu.h> #include <linux/cpu_pm.h> #include <linux/kernel.h> #include <linux/linkage.h> #include <linux/irqflags.h> #include <linux/init.h> #include <linux/percpu.h> #include <linux/prctl.h> #include <linux/preempt.h> #include <linux/ptrace.h> #include <linux/sched/signal.h> #include <linux/sched/task_stack.h> #include <linux/signal.h> #include <linux/slab.h> #include <linux/stddef.h> #include <linux/sysctl.h> #include <linux/swab.h> #include <asm/esr.h> #include <asm/fpsimd.h> #include <asm/cpufeature.h> #include <asm/cputype.h> #include <asm/processor.h> #include <asm/simd.h> #include <asm/sigcontext.h> #include <asm/sysreg.h> #include <asm/traps.h> #include <asm/virt.h> #define FPEXC_IOF (1 << 0) #define FPEXC_DZF (1 << 1) #define FPEXC_OFF (1 << 2) #define FPEXC_UFF (1 << 3) #define FPEXC_IXF (1 << 4) #define FPEXC_IDF (1 << 7) /* * (Note: in this discussion, statements about FPSIMD apply equally to SVE.) * * In order to reduce the number of times the FPSIMD state is needlessly saved * and restored, we need to keep track of two things: * (a) for each task, we need to remember which CPU was the last one to have * the task's FPSIMD state loaded into its FPSIMD registers; * (b) for each CPU, we need to remember which task's userland FPSIMD state has * been loaded into its FPSIMD registers most recently, or whether it has * been used to perform kernel mode NEON in the meantime. * * For (a), we add a fpsimd_cpu field to thread_struct, which gets updated to * the id of the current CPU every time the state is loaded onto a CPU. For (b), * we add the per-cpu variable 'fpsimd_last_state' (below), which contains the * address of the userland FPSIMD state of the task that was loaded onto the CPU * the most recently, or NULL if kernel mode NEON has been performed after that. * * With this in place, we no longer have to restore the next FPSIMD state right * when switching between tasks. Instead, we can defer this check to userland * resume, at which time we verify whether the CPU's fpsimd_last_state and the * task's fpsimd_cpu are still mutually in sync. If this is the case, we * can omit the FPSIMD restore. * * As an optimization, we use the thread_info flag TIF_FOREIGN_FPSTATE to * indicate whether or not the userland FPSIMD state of the current task is * present in the registers. The flag is set unless the FPSIMD registers of this * CPU currently contain the most recent userland FPSIMD state of the current * task. * * In order to allow softirq handlers to use FPSIMD, kernel_neon_begin() may * save the task's FPSIMD context back to task_struct from softirq context. * To prevent this from racing with the manipulation of the task's FPSIMD state * from task context and thereby corrupting the state, it is necessary to * protect any manipulation of a task's fpsimd_state or TIF_FOREIGN_FPSTATE * flag with {, __}get_cpu_fpsimd_context(). This will still allow softirqs to * run but prevent them to use FPSIMD. * * For a certain task, the sequence may look something like this: * - the task gets scheduled in; if both the task's fpsimd_cpu field * contains the id of the current CPU, and the CPU's fpsimd_last_state per-cpu * variable points to the task's fpsimd_state, the TIF_FOREIGN_FPSTATE flag is * cleared, otherwise it is set; * * - the task returns to userland; if TIF_FOREIGN_FPSTATE is set, the task's * userland FPSIMD state is copied from memory to the registers, the task's * fpsimd_cpu field is set to the id of the current CPU, the current * CPU's fpsimd_last_state pointer is set to this task's fpsimd_state and the * TIF_FOREIGN_FPSTATE flag is cleared; * * - the task executes an ordinary syscall; upon return to userland, the * TIF_FOREIGN_FPSTATE flag will still be cleared, so no FPSIMD state is * restored; * * - the task executes a syscall which executes some NEON instructions; this is * preceded by a call to kernel_neon_begin(), which copies the task's FPSIMD * register contents to memory, clears the fpsimd_last_state per-cpu variable * and sets the TIF_FOREIGN_FPSTATE flag; * * - the task gets preempted after kernel_neon_end() is called; as we have not * returned from the 2nd syscall yet, TIF_FOREIGN_FPSTATE is still set so * whatever is in the FPSIMD registers is not saved to memory, but discarded. */ struct fpsimd_last_state_struct { struct user_fpsimd_state *st; void *sve_state; unsigned int sve_vl; }; static DEFINE_PER_CPU(struct fpsimd_last_state_struct, fpsimd_last_state); /* Default VL for tasks that don't set it explicitly: */ static int __sve_default_vl = -1; static int get_sve_default_vl(void) { return READ_ONCE(__sve_default_vl); } #ifdef CONFIG_ARM64_SVE static void set_sve_default_vl(int val) { WRITE_ONCE(__sve_default_vl, val); } /* Maximum supported vector length across all CPUs (initially poisoned) */ int __ro_after_init sve_max_vl = SVE_VL_MIN; int __ro_after_init sve_max_virtualisable_vl = SVE_VL_MIN; /* * Set of available vector lengths, * where length vq encoded as bit __vq_to_bit(vq): */ __ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX); /* Set of vector lengths present on at least one cpu: */ static __ro_after_init DECLARE_BITMAP(sve_vq_partial_map, SVE_VQ_MAX); static void __percpu *efi_sve_state; #else /* ! CONFIG_ARM64_SVE */ /* Dummy declaration for code that will be optimised out: */ extern __ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX); extern __ro_after_init DECLARE_BITMAP(sve_vq_partial_map, SVE_VQ_MAX); extern void __percpu *efi_sve_state; #endif /* ! CONFIG_ARM64_SVE */ DEFINE_PER_CPU(bool, fpsimd_context_busy); EXPORT_PER_CPU_SYMBOL(fpsimd_context_busy); static void __get_cpu_fpsimd_context(void) { bool busy = __this_cpu_xchg(fpsimd_context_busy, true); WARN_ON(busy); } /* * Claim ownership of the CPU FPSIMD context for use by the calling context. * * The caller may freely manipulate the FPSIMD context metadata until * put_cpu_fpsimd_context() is called. * * The double-underscore version must only be called if you know the task * can't be preempted. */ static void get_cpu_fpsimd_context(void) { preempt_disable(); __get_cpu_fpsimd_context(); } static void __put_cpu_fpsimd_context(void) { bool busy = __this_cpu_xchg(fpsimd_context_busy, false); WARN_ON(!busy); /* No matching get_cpu_fpsimd_context()? */ } /* * Release the CPU FPSIMD context. * * Must be called from a context in which get_cpu_fpsimd_context() was * previously called, with no call to put_cpu_fpsimd_context() in the * meantime. */ static void put_cpu_fpsimd_context(void) { __put_cpu_fpsimd_context(); preempt_enable(); } static bool have_cpu_fpsimd_context(void) { return !preemptible() && __this_cpu_read(fpsimd_context_busy); } /* * Call __sve_free() directly only if you know task can't be scheduled * or preempted. */ static void __sve_free(struct task_struct *task) { kfree(task->thread.sve_state); task->thread.sve_state = NULL; } static void sve_free(struct task_struct *task) { WARN_ON(test_tsk_thread_flag(task, TIF_SVE)); __sve_free(task); } /* * TIF_SVE controls whether a task can use SVE without trapping while * in userspace, and also the way a task's FPSIMD/SVE state is stored * in thread_struct. * * The kernel uses this flag to track whether a user task is actively * using SVE, and therefore whether full SVE register state needs to * be tracked. If not, the cheaper FPSIMD context handling code can * be used instead of the more costly SVE equivalents. * * * TIF_SVE set: * * The task can execute SVE instructions while in userspace without * trapping to the kernel. * * When stored, Z0-Z31 (incorporating Vn in bits[127:0] or the * corresponding Zn), P0-P15 and FFR are encoded in in * task->thread.sve_state, formatted appropriately for vector * length task->thread.sve_vl. * * task->thread.sve_state must point to a valid buffer at least * sve_state_size(task) bytes in size. * * During any syscall, the kernel may optionally clear TIF_SVE and * discard the vector state except for the FPSIMD subset. * * * TIF_SVE clear: * * An attempt by the user task to execute an SVE instruction causes * do_sve_acc() to be called, which does some preparation and then * sets TIF_SVE. * * When stored, FPSIMD registers V0-V31 are encoded in * task->thread.uw.fpsimd_state; bits [max : 128] for each of Z0-Z31 are * logically zero but not stored anywhere; P0-P15 and FFR are not * stored and have unspecified values from userspace's point of * view. For hygiene purposes, the kernel zeroes them on next use, * but userspace is discouraged from relying on this. * * task->thread.sve_state does not need to be non-NULL, valid or any * particular size: it must not be dereferenced. * * * FPSR and FPCR are always stored in task->thread.uw.fpsimd_state * irrespective of whether TIF_SVE is clear or set, since these are * not vector length dependent. */ /* * Update current's FPSIMD/SVE registers from thread_struct. * * This function should be called only when the FPSIMD/SVE state in * thread_struct is known to be up to date, when preparing to enter * userspace. */ static void task_fpsimd_load(void) { WARN_ON(!system_supports_fpsimd()); WARN_ON(!have_cpu_fpsimd_context()); if (system_supports_sve() && test_thread_flag(TIF_SVE)) sve_load_state(sve_pffr(¤t->thread), ¤t->thread.uw.fpsimd_state.fpsr, sve_vq_from_vl(current->thread.sve_vl) - 1); else fpsimd_load_state(¤t->thread.uw.fpsimd_state); } /* * Ensure FPSIMD/SVE storage in memory for the loaded context is up to * date with respect to the CPU registers. */ static void fpsimd_save(void) { struct fpsimd_last_state_struct const *last = this_cpu_ptr(&fpsimd_last_state); /* set by fpsimd_bind_task_to_cpu() or fpsimd_bind_state_to_cpu() */ WARN_ON(!system_supports_fpsimd()); WARN_ON(!have_cpu_fpsimd_context()); if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) { if (system_supports_sve() && test_thread_flag(TIF_SVE)) { if (WARN_ON(sve_get_vl() != last->sve_vl)) { /* * Can't save the user regs, so current would * re-enter user with corrupt state. * There's no way to recover, so kill it: */ force_signal_inject(SIGKILL, SI_KERNEL, 0); return; } sve_save_state((char *)last->sve_state + sve_ffr_offset(last->sve_vl), &last->st->fpsr); } else fpsimd_save_state(last->st); } } /* * All vector length selection from userspace comes through here. * We're on a slow path, so some sanity-checks are included. * If things go wrong there's a bug somewhere, but try to fall back to a * safe choice. */ static unsigned int find_supported_vector_length(unsigned int vl) { int bit; int max_vl = sve_max_vl; if (WARN_ON(!sve_vl_valid(vl))) vl = SVE_VL_MIN; if (WARN_ON(!sve_vl_valid(max_vl))) max_vl = SVE_VL_MIN; if (vl > max_vl) vl = max_vl; bit = find_next_bit(sve_vq_map, SVE_VQ_MAX, __vq_to_bit(sve_vq_from_vl(vl))); return sve_vl_from_vq(__bit_to_vq(bit)); } #if defined(CONFIG_ARM64_SVE) && defined(CONFIG_SYSCTL) static int sve_proc_do_default_vl(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { int ret; int vl = get_sve_default_vl(); struct ctl_table tmp_table = { .data = &vl, .maxlen = sizeof(vl), }; ret = proc_dointvec(&tmp_table, write, buffer, lenp, ppos); if (ret || !write) return ret; /* Writing -1 has the special meaning "set to max": */ if (vl == -1) vl = sve_max_vl; if (!sve_vl_valid(vl)) return -EINVAL; set_sve_default_vl(find_supported_vector_length(vl)); return 0; } static struct ctl_table sve_default_vl_table[] = { { .procname = "sve_default_vector_length", .mode = 0644, .proc_handler = sve_proc_do_default_vl, }, { } }; static int __init sve_sysctl_init(void) { if (system_supports_sve()) if (!register_sysctl("abi", sve_default_vl_table)) return -EINVAL; return 0; } #else /* ! (CONFIG_ARM64_SVE && CONFIG_SYSCTL) */ static int __init sve_sysctl_init(void) { return 0; } #endif /* ! (CONFIG_ARM64_SVE && CONFIG_SYSCTL) */ #define ZREG(sve_state, vq, n) ((char *)(sve_state) + \ (SVE_SIG_ZREG_OFFSET(vq, n) - SVE_SIG_REGS_OFFSET)) #ifdef CONFIG_CPU_BIG_ENDIAN static __uint128_t arm64_cpu_to_le128(__uint128_t x) { u64 a = swab64(x); u64 b = swab64(x >> 64); return ((__uint128_t)a << 64) | b; } #else static __uint128_t arm64_cpu_to_le128(__uint128_t x) { return x; } #endif #define arm64_le128_to_cpu(x) arm64_cpu_to_le128(x) static void __fpsimd_to_sve(void *sst, struct user_fpsimd_state const *fst, unsigned int vq) { unsigned int i; __uint128_t *p; for (i = 0; i < SVE_NUM_ZREGS; ++i) { p = (__uint128_t *)ZREG(sst, vq, i); *p = arm64_cpu_to_le128(fst->vregs[i]); } } /* * Transfer the FPSIMD state in task->thread.uw.fpsimd_state to * task->thread.sve_state. * * Task can be a non-runnable task, or current. In the latter case, * the caller must have ownership of the cpu FPSIMD context before calling * this function. * task->thread.sve_state must point to at least sve_state_size(task) * bytes of allocated kernel memory. * task->thread.uw.fpsimd_state must be up to date before calling this * function. */ static void fpsimd_to_sve(struct task_struct *task) { unsigned int vq; void *sst = task->thread.sve_state; struct user_fpsimd_state const *fst = &task->thread.uw.fpsimd_state; if (!system_supports_sve()) return; vq = sve_vq_from_vl(task->thread.sve_vl); __fpsimd_to_sve(sst, fst, vq); } /* * Transfer the SVE state in task->thread.sve_state to * task->thread.uw.fpsimd_state. * * Task can be a non-runnable task, or current. In the latter case, * the caller must have ownership of the cpu FPSIMD context before calling * this function. * task->thread.sve_state must point to at least sve_state_size(task) * bytes of allocated kernel memory. * task->thread.sve_state must be up to date before calling this function. */ static void sve_to_fpsimd(struct task_struct *task) { unsigned int vq; void const *sst = task->thread.sve_state; struct user_fpsimd_state *fst = &task->thread.uw.fpsimd_state; unsigned int i; __uint128_t const *p; if (!system_supports_sve()) return; vq = sve_vq_from_vl(task->thread.sve_vl); for (i = 0; i < SVE_NUM_ZREGS; ++i) { p = (__uint128_t const *)ZREG(sst, vq, i); fst->vregs[i] = arm64_le128_to_cpu(*p); } } #ifdef CONFIG_ARM64_SVE /* * Return how many bytes of memory are required to store the full SVE * state for task, given task's currently configured vector length. */ size_t sve_state_size(struct task_struct const *task) { return SVE_SIG_REGS_SIZE(sve_vq_from_vl(task->thread.sve_vl)); } /* * Ensure that task->thread.sve_state is allocated and sufficiently large. * * This function should be used only in preparation for replacing * task->thread.sve_state with new data. The memory is always zeroed * here to prevent stale data from showing through: this is done in * the interest of testability and predictability: except in the * do_sve_acc() case, there is no ABI requirement to hide stale data * written previously be task. */ void sve_alloc(struct task_struct *task) { if (task->thread.sve_state) { memset(task->thread.sve_state, 0, sve_state_size(current)); return; } /* This is a small allocation (maximum ~8KB) and Should Not Fail. */ task->thread.sve_state = kzalloc(sve_state_size(task), GFP_KERNEL); /* * If future SVE revisions can have larger vectors though, * this may cease to be true: */ BUG_ON(!task->thread.sve_state); } /* * Ensure that task->thread.sve_state is up to date with respect to * the user task, irrespective of when SVE is in use or not. * * This should only be called by ptrace. task must be non-runnable. * task->thread.sve_state must point to at least sve_state_size(task) * bytes of allocated kernel memory. */ void fpsimd_sync_to_sve(struct task_struct *task) { if (!test_tsk_thread_flag(task, TIF_SVE)) fpsimd_to_sve(task); } /* * Ensure that task->thread.uw.fpsimd_state is up to date with respect to * the user task, irrespective of whether SVE is in use or not. * * This should only be called by ptrace. task must be non-runnable. * task->thread.sve_state must point to at least sve_state_size(task) * bytes of allocated kernel memory. */ void sve_sync_to_fpsimd(struct task_struct *task) { if (test_tsk_thread_flag(task, TIF_SVE)) sve_to_fpsimd(task); } /* * Ensure that task->thread.sve_state is up to date with respect to * the task->thread.uw.fpsimd_state. * * This should only be called by ptrace to merge new FPSIMD register * values into a task for which SVE is currently active. * task must be non-runnable. * task->thread.sve_state must point to at least sve_state_size(task) * bytes of allocated kernel memory. * task->thread.uw.fpsimd_state must already have been initialised with * the new FPSIMD register values to be merged in. */ void sve_sync_from_fpsimd_zeropad(struct task_struct *task) { unsigned int vq; void *sst = task->thread.sve_state; struct user_fpsimd_state const *fst = &task->thread.uw.fpsimd_state; if (!test_tsk_thread_flag(task, TIF_SVE)) return; vq = sve_vq_from_vl(task->thread.sve_vl); memset(sst, 0, SVE_SIG_REGS_SIZE(vq)); __fpsimd_to_sve(sst, fst, vq); } int sve_set_vector_length(struct task_struct *task, unsigned long vl, unsigned long flags) { if (flags & ~(unsigned long)(PR_SVE_VL_INHERIT | PR_SVE_SET_VL_ONEXEC)) return -EINVAL; if (!sve_vl_valid(vl)) return -EINVAL; /* * Clamp to the maximum vector length that VL-agnostic SVE code can * work with. A flag may be assigned in the future to allow setting * of larger vector lengths without confusing older software. */ if (vl > SVE_VL_ARCH_MAX) vl = SVE_VL_ARCH_MAX; vl = find_supported_vector_length(vl); if (flags & (PR_SVE_VL_INHERIT | PR_SVE_SET_VL_ONEXEC)) task->thread.sve_vl_onexec = vl; else /* Reset VL to system default on next exec: */ task->thread.sve_vl_onexec = 0; /* Only actually set the VL if not deferred: */ if (flags & PR_SVE_SET_VL_ONEXEC) goto out; if (vl == task->thread.sve_vl) goto out; /* * To ensure the FPSIMD bits of the SVE vector registers are preserved, * write any live register state back to task_struct, and convert to a * non-SVE thread. */ if (task == current) { get_cpu_fpsimd_context(); fpsimd_save(); } fpsimd_flush_task_state(task); if (test_and_clear_tsk_thread_flag(task, TIF_SVE)) sve_to_fpsimd(task); if (task == current) put_cpu_fpsimd_context(); /* * Force reallocation of task SVE state to the correct size * on next use: */ sve_free(task); task->thread.sve_vl = vl; out: update_tsk_thread_flag(task, TIF_SVE_VL_INHERIT, flags & PR_SVE_VL_INHERIT); return 0; } /* * Encode the current vector length and flags for return. * This is only required for prctl(): ptrace has separate fields * * flags are as for sve_set_vector_length(). */ static int sve_prctl_status(unsigned long flags) { int ret; if (flags & PR_SVE_SET_VL_ONEXEC) ret = current->thread.sve_vl_onexec; else ret = current->thread.sve_vl; if (test_thread_flag(TIF_SVE_VL_INHERIT)) ret |= PR_SVE_VL_INHERIT; return ret; } /* PR_SVE_SET_VL */ int sve_set_current_vl(unsigned long arg) { unsigned long vl, flags; int ret; vl = arg & PR_SVE_VL_LEN_MASK; flags = arg & ~vl; if (!system_supports_sve()) return -EINVAL; ret = sve_set_vector_length(current, vl, flags); if (ret) return ret; return sve_prctl_status(flags); } /* PR_SVE_GET_VL */ int sve_get_current_vl(void) { if (!system_supports_sve()) return -EINVAL; return sve_prctl_status(0); } static void sve_probe_vqs(DECLARE_BITMAP(map, SVE_VQ_MAX)) { unsigned int vq, vl; unsigned long zcr; bitmap_zero(map, SVE_VQ_MAX); zcr = ZCR_ELx_LEN_MASK; zcr = read_sysreg_s(SYS_ZCR_EL1) & ~zcr; for (vq = SVE_VQ_MAX; vq >= SVE_VQ_MIN; --vq) { write_sysreg_s(zcr | (vq - 1), SYS_ZCR_EL1); /* self-syncing */ vl = sve_get_vl(); vq = sve_vq_from_vl(vl); /* skip intervening lengths */ set_bit(__vq_to_bit(vq), map); } } /* * Initialise the set of known supported VQs for the boot CPU. * This is called during kernel boot, before secondary CPUs are brought up. */ void __init sve_init_vq_map(void) { sve_probe_vqs(sve_vq_map); bitmap_copy(sve_vq_partial_map, sve_vq_map, SVE_VQ_MAX); } /* * If we haven't committed to the set of supported VQs yet, filter out * those not supported by the current CPU. * This function is called during the bring-up of early secondary CPUs only. */ void sve_update_vq_map(void) { DECLARE_BITMAP(tmp_map, SVE_VQ_MAX); sve_probe_vqs(tmp_map); bitmap_and(sve_vq_map, sve_vq_map, tmp_map, SVE_VQ_MAX); bitmap_or(sve_vq_partial_map, sve_vq_partial_map, tmp_map, SVE_VQ_MAX); } /* * Check whether the current CPU supports all VQs in the committed set. * This function is called during the bring-up of late secondary CPUs only. */ int sve_verify_vq_map(void) { DECLARE_BITMAP(tmp_map, SVE_VQ_MAX); unsigned long b; sve_probe_vqs(tmp_map); bitmap_complement(tmp_map, tmp_map, SVE_VQ_MAX); if (bitmap_intersects(tmp_map, sve_vq_map, SVE_VQ_MAX)) { pr_warn("SVE: cpu%d: Required vector length(s) missing\n", smp_processor_id()); return -EINVAL; } if (!IS_ENABLED(CONFIG_KVM) || !is_hyp_mode_available()) return 0; /* * For KVM, it is necessary to ensure that this CPU doesn't * support any vector length that guests may have probed as * unsupported. */ /* Recover the set of supported VQs: */ bitmap_complement(tmp_map, tmp_map, SVE_VQ_MAX); /* Find VQs supported that are not globally supported: */ bitmap_andnot(tmp_map, tmp_map, sve_vq_map, SVE_VQ_MAX); /* Find the lowest such VQ, if any: */ b = find_last_bit(tmp_map, SVE_VQ_MAX); if (b >= SVE_VQ_MAX) return 0; /* no mismatches */ /* * Mismatches above sve_max_virtualisable_vl are fine, since * no guest is allowed to configure ZCR_EL2.LEN to exceed this: */ if (sve_vl_from_vq(__bit_to_vq(b)) <= sve_max_virtualisable_vl) { pr_warn("SVE: cpu%d: Unsupported vector length(s) present\n", smp_processor_id()); return -EINVAL; } return 0; } static void __init sve_efi_setup(void) { if (!IS_ENABLED(CONFIG_EFI)) return; /* * alloc_percpu() warns and prints a backtrace if this goes wrong. * This is evidence of a crippled system and we are returning void, * so no attempt is made to handle this situation here. */ if (!sve_vl_valid(sve_max_vl)) goto fail; efi_sve_state = __alloc_percpu( SVE_SIG_REGS_SIZE(sve_vq_from_vl(sve_max_vl)), SVE_VQ_BYTES); if (!efi_sve_state) goto fail; return; fail: panic("Cannot allocate percpu memory for EFI SVE save/restore"); } /* * Enable SVE for EL1. * Intended for use by the cpufeatures code during CPU boot. */ void sve_kernel_enable(const struct arm64_cpu_capabilities *__always_unused p) { write_sysreg(read_sysreg(CPACR_EL1) | CPACR_EL1_ZEN_EL1EN, CPACR_EL1); isb(); } /* * Read the pseudo-ZCR used by cpufeatures to identify the supported SVE * vector length. * * Use only if SVE is present. * This function clobbers the SVE vector length. */ u64 read_zcr_features(void) { u64 zcr; unsigned int vq_max; /* * Set the maximum possible VL, and write zeroes to all other * bits to see if they stick. */ sve_kernel_enable(NULL); write_sysreg_s(ZCR_ELx_LEN_MASK, SYS_ZCR_EL1); zcr = read_sysreg_s(SYS_ZCR_EL1); zcr &= ~(u64)ZCR_ELx_LEN_MASK; /* find sticky 1s outside LEN field */ vq_max = sve_vq_from_vl(sve_get_vl()); zcr |= vq_max - 1; /* set LEN field to maximum effective value */ return zcr; } void __init sve_setup(void) { u64 zcr; DECLARE_BITMAP(tmp_map, SVE_VQ_MAX); unsigned long b; if (!system_supports_sve()) return; /* * The SVE architecture mandates support for 128-bit vectors, * so sve_vq_map must have at least SVE_VQ_MIN set. * If something went wrong, at least try to patch it up: */ if (WARN_ON(!test_bit(__vq_to_bit(SVE_VQ_MIN), sve_vq_map))) set_bit(__vq_to_bit(SVE_VQ_MIN), sve_vq_map); zcr = read_sanitised_ftr_reg(SYS_ZCR_EL1); sve_max_vl = sve_vl_from_vq((zcr & ZCR_ELx_LEN_MASK) + 1); /* * Sanity-check that the max VL we determined through CPU features * corresponds properly to sve_vq_map. If not, do our best: */ if (WARN_ON(sve_max_vl != find_supported_vector_length(sve_max_vl))) sve_max_vl = find_supported_vector_length(sve_max_vl); /* * For the default VL, pick the maximum supported value <= 64. * VL == 64 is guaranteed not to grow the signal frame. */ set_sve_default_vl(find_supported_vector_length(64)); bitmap_andnot(tmp_map, sve_vq_partial_map, sve_vq_map, SVE_VQ_MAX); b = find_last_bit(tmp_map, SVE_VQ_MAX); if (b >= SVE_VQ_MAX) /* No non-virtualisable VLs found */ sve_max_virtualisable_vl = SVE_VQ_MAX; else if (WARN_ON(b == SVE_VQ_MAX - 1)) /* No virtualisable VLs? This is architecturally forbidden. */ sve_max_virtualisable_vl = SVE_VQ_MIN; else /* b + 1 < SVE_VQ_MAX */ sve_max_virtualisable_vl = sve_vl_from_vq(__bit_to_vq(b + 1)); if (sve_max_virtualisable_vl > sve_max_vl) sve_max_virtualisable_vl = sve_max_vl; pr_info("SVE: maximum available vector length %u bytes per vector\n", sve_max_vl); pr_info("SVE: default vector length %u bytes per vector\n", get_sve_default_vl()); /* KVM decides whether to support mismatched systems. Just warn here: */ if (sve_max_virtualisable_vl < sve_max_vl) pr_warn("SVE: unvirtualisable vector lengths present\n"); sve_efi_setup(); } /* * Called from the put_task_struct() path, which cannot get here * unless dead_task is really dead and not schedulable. */ void fpsimd_release_task(struct task_struct *dead_task) { __sve_free(dead_task); } #endif /* CONFIG_ARM64_SVE */ /* * Trapped SVE access * * Storage is allocated for the full SVE state, the current FPSIMD * register contents are migrated across, and TIF_SVE is set so that * the SVE access trap will be disabled the next time this task * reaches ret_to_user. * * TIF_SVE should be clear on entry: otherwise, task_fpsimd_load() * would have disabled the SVE access trap for userspace during * ret_to_user, making an SVE access trap impossible in that case. */ void do_sve_acc(unsigned int esr, struct pt_regs *regs) { /* Even if we chose not to use SVE, the hardware could still trap: */ if (unlikely(!system_supports_sve()) || WARN_ON(is_compat_task())) { force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc); return; } sve_alloc(current); get_cpu_fpsimd_context(); fpsimd_save(); /* Force ret_to_user to reload the registers: */ fpsimd_flush_task_state(current); fpsimd_to_sve(current); if (test_and_set_thread_flag(TIF_SVE)) WARN_ON(1); /* SVE access shouldn't have trapped */ put_cpu_fpsimd_context(); } /* * Trapped FP/ASIMD access. */ void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs) { /* TODO: implement lazy context saving/restoring */ WARN_ON(1); } /* * Raise a SIGFPE for the current process. */ void do_fpsimd_exc(unsigned int esr, struct pt_regs *regs) { unsigned int si_code = FPE_FLTUNK; if (esr & ESR_ELx_FP_EXC_TFV) { if (esr & FPEXC_IOF) si_code = FPE_FLTINV; else if (esr & FPEXC_DZF) si_code = FPE_FLTDIV; else if (esr & FPEXC_OFF) si_code = FPE_FLTOVF; else if (esr & FPEXC_UFF) si_code = FPE_FLTUND; else if (esr & FPEXC_IXF) si_code = FPE_FLTRES; } send_sig_fault(SIGFPE, si_code, (void __user *)instruction_pointer(regs), current); } void fpsimd_thread_switch(struct task_struct *next) { bool wrong_task, wrong_cpu; if (!system_supports_fpsimd()) return; __get_cpu_fpsimd_context(); /* Save unsaved fpsimd state, if any: */ fpsimd_save(); /* * Fix up TIF_FOREIGN_FPSTATE to correctly describe next's * state. For kernel threads, FPSIMD registers are never loaded * and wrong_task and wrong_cpu will always be true. */ wrong_task = __this_cpu_read(fpsimd_last_state.st) != &next->thread.uw.fpsimd_state; wrong_cpu = next->thread.fpsimd_cpu != smp_processor_id(); update_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE, wrong_task || wrong_cpu); __put_cpu_fpsimd_context(); } void fpsimd_flush_thread(void) { int vl, supported_vl; if (!system_supports_fpsimd()) return; get_cpu_fpsimd_context(); fpsimd_flush_task_state(current); memset(¤t->thread.uw.fpsimd_state, 0, sizeof(current->thread.uw.fpsimd_state)); if (system_supports_sve()) { clear_thread_flag(TIF_SVE); sve_free(current); /* * Reset the task vector length as required. * This is where we ensure that all user tasks have a valid * vector length configured: no kernel task can become a user * task without an exec and hence a call to this function. * By the time the first call to this function is made, all * early hardware probing is complete, so __sve_default_vl * should be valid. * If a bug causes this to go wrong, we make some noise and * try to fudge thread.sve_vl to a safe value here. */ vl = current->thread.sve_vl_onexec ? current->thread.sve_vl_onexec : get_sve_default_vl(); if (WARN_ON(!sve_vl_valid(vl))) vl = SVE_VL_MIN; supported_vl = find_supported_vector_length(vl); if (WARN_ON(supported_vl != vl)) vl = supported_vl; current->thread.sve_vl = vl; /* * If the task is not set to inherit, ensure that the vector * length will be reset by a subsequent exec: */ if (!test_thread_flag(TIF_SVE_VL_INHERIT)) current->thread.sve_vl_onexec = 0; } put_cpu_fpsimd_context(); } /* * Save the userland FPSIMD state of 'current' to memory, but only if the state * currently held in the registers does in fact belong to 'current' */ void fpsimd_preserve_current_state(void) { if (!system_supports_fpsimd()) return; get_cpu_fpsimd_context(); fpsimd_save(); put_cpu_fpsimd_context(); } /* * Like fpsimd_preserve_current_state(), but ensure that * current->thread.uw.fpsimd_state is updated so that it can be copied to * the signal frame. */ void fpsimd_signal_preserve_current_state(void) { fpsimd_preserve_current_state(); if (system_supports_sve() && test_thread_flag(TIF_SVE)) sve_to_fpsimd(current); } /* * Associate current's FPSIMD context with this cpu * The caller must have ownership of the cpu FPSIMD context before calling * this function. */ void fpsimd_bind_task_to_cpu(void) { struct fpsimd_last_state_struct *last = this_cpu_ptr(&fpsimd_last_state); WARN_ON(!system_supports_fpsimd()); last->st = ¤t->thread.uw.fpsimd_state; last->sve_state = current->thread.sve_state; last->sve_vl = current->thread.sve_vl; current->thread.fpsimd_cpu = smp_processor_id(); if (system_supports_sve()) { /* Toggle SVE trapping for userspace if needed */ if (test_thread_flag(TIF_SVE)) sve_user_enable(); else sve_user_disable(); /* Serialised by exception return to user */ } } void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *st, void *sve_state, unsigned int sve_vl) { struct fpsimd_last_state_struct *last = this_cpu_ptr(&fpsimd_last_state); WARN_ON(!system_supports_fpsimd()); WARN_ON(!in_softirq() && !irqs_disabled()); last->st = st; last->sve_state = sve_state; last->sve_vl = sve_vl; } /* * Load the userland FPSIMD state of 'current' from memory, but only if the * FPSIMD state already held in the registers is /not/ the most recent FPSIMD * state of 'current' */ void fpsimd_restore_current_state(void) { /* * For the tasks that were created before we detected the absence of * FP/SIMD, the TIF_FOREIGN_FPSTATE could be set via fpsimd_thread_switch(), * e.g, init. This could be then inherited by the children processes. * If we later detect that the system doesn't support FP/SIMD, * we must clear the flag for all the tasks to indicate that the * FPSTATE is clean (as we can't have one) to avoid looping for ever in * do_notify_resume(). */ if (!system_supports_fpsimd()) { clear_thread_flag(TIF_FOREIGN_FPSTATE); return; } get_cpu_fpsimd_context(); if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) { task_fpsimd_load(); fpsimd_bind_task_to_cpu(); } put_cpu_fpsimd_context(); } /* * Load an updated userland FPSIMD state for 'current' from memory and set the * flag that indicates that the FPSIMD register contents are the most recent * FPSIMD state of 'current' */ void fpsimd_update_current_state(struct user_fpsimd_state const *state) { if (WARN_ON(!system_supports_fpsimd())) return; get_cpu_fpsimd_context(); current->thread.uw.fpsimd_state = *state; if (system_supports_sve() && test_thread_flag(TIF_SVE)) fpsimd_to_sve(current); task_fpsimd_load(); fpsimd_bind_task_to_cpu(); clear_thread_flag(TIF_FOREIGN_FPSTATE); put_cpu_fpsimd_context(); } /* * Invalidate live CPU copies of task t's FPSIMD state * * This function may be called with preemption enabled. The barrier() * ensures that the assignment to fpsimd_cpu is visible to any * preemption/softirq that could race with set_tsk_thread_flag(), so * that TIF_FOREIGN_FPSTATE cannot be spuriously re-cleared. * * The final barrier ensures that TIF_FOREIGN_FPSTATE is seen set by any * subsequent code. */ void fpsimd_flush_task_state(struct task_struct *t) { t->thread.fpsimd_cpu = NR_CPUS; /* * If we don't support fpsimd, bail out after we have * reset the fpsimd_cpu for this task and clear the * FPSTATE. */ if (!system_supports_fpsimd()) return; barrier(); set_tsk_thread_flag(t, TIF_FOREIGN_FPSTATE); barrier(); } /* * Invalidate any task's FPSIMD state that is present on this cpu. * The FPSIMD context should be acquired with get_cpu_fpsimd_context() * before calling this function. */ static void fpsimd_flush_cpu_state(void) { WARN_ON(!system_supports_fpsimd()); __this_cpu_write(fpsimd_last_state.st, NULL); set_thread_flag(TIF_FOREIGN_FPSTATE); } /* * Save the FPSIMD state to memory and invalidate cpu view. * This function must be called with preemption disabled. */ void fpsimd_save_and_flush_cpu_state(void) { if (!system_supports_fpsimd()) return; WARN_ON(preemptible()); __get_cpu_fpsimd_context(); fpsimd_save(); fpsimd_flush_cpu_state(); __put_cpu_fpsimd_context(); } #ifdef CONFIG_KERNEL_MODE_NEON /* * Kernel-side NEON support functions */ /* * kernel_neon_begin(): obtain the CPU FPSIMD registers for use by the calling * context * * Must not be called unless may_use_simd() returns true. * Task context in the FPSIMD registers is saved back to memory as necessary. * * A matching call to kernel_neon_end() must be made before returning from the * calling context. * * The caller may freely use the FPSIMD registers until kernel_neon_end() is * called. */ void kernel_neon_begin(void) { if (WARN_ON(!system_supports_fpsimd())) return; BUG_ON(!may_use_simd()); get_cpu_fpsimd_context(); /* Save unsaved fpsimd state, if any: */ fpsimd_save(); /* Invalidate any task state remaining in the fpsimd regs: */ fpsimd_flush_cpu_state(); } EXPORT_SYMBOL(kernel_neon_begin); /* * kernel_neon_end(): give the CPU FPSIMD registers back to the current task * * Must be called from a context in which kernel_neon_begin() was previously * called, with no call to kernel_neon_end() in the meantime. * * The caller must not use the FPSIMD registers after this function is called, * unless kernel_neon_begin() is called again in the meantime. */ void kernel_neon_end(void) { if (!system_supports_fpsimd()) return; put_cpu_fpsimd_context(); } EXPORT_SYMBOL(kernel_neon_end); #ifdef CONFIG_EFI static DEFINE_PER_CPU(struct user_fpsimd_state, efi_fpsimd_state); static DEFINE_PER_CPU(bool, efi_fpsimd_state_used); static DEFINE_PER_CPU(bool, efi_sve_state_used); /* * EFI runtime services support functions * * The ABI for EFI runtime services allows EFI to use FPSIMD during the call. * This means that for EFI (and only for EFI), we have to assume that FPSIMD * is always used rather than being an optional accelerator. * * These functions provide the necessary support for ensuring FPSIMD * save/restore in the contexts from which EFI is used. * * Do not use them for any other purpose -- if tempted to do so, you are * either doing something wrong or you need to propose some refactoring. */ /* * __efi_fpsimd_begin(): prepare FPSIMD for making an EFI runtime services call */ void __efi_fpsimd_begin(void) { if (!system_supports_fpsimd()) return; WARN_ON(preemptible()); if (may_use_simd()) { kernel_neon_begin(); } else { /* * If !efi_sve_state, SVE can't be in use yet and doesn't need * preserving: */ if (system_supports_sve() && likely(efi_sve_state)) { char *sve_state = this_cpu_ptr(efi_sve_state); __this_cpu_write(efi_sve_state_used, true); sve_save_state(sve_state + sve_ffr_offset(sve_max_vl), &this_cpu_ptr(&efi_fpsimd_state)->fpsr); } else { fpsimd_save_state(this_cpu_ptr(&efi_fpsimd_state)); } __this_cpu_write(efi_fpsimd_state_used, true); } } /* * __efi_fpsimd_end(): clean up FPSIMD after an EFI runtime services call */ void __efi_fpsimd_end(void) { if (!system_supports_fpsimd()) return; if (!__this_cpu_xchg(efi_fpsimd_state_used, false)) { kernel_neon_end(); } else { if (system_supports_sve() && likely(__this_cpu_read(efi_sve_state_used))) { char const *sve_state = this_cpu_ptr(efi_sve_state); sve_load_state(sve_state + sve_ffr_offset(sve_max_vl), &this_cpu_ptr(&efi_fpsimd_state)->fpsr, sve_vq_from_vl(sve_get_vl()) - 1); __this_cpu_write(efi_sve_state_used, false); } else { fpsimd_load_state(this_cpu_ptr(&efi_fpsimd_state)); } } } #endif /* CONFIG_EFI */ #endif /* CONFIG_KERNEL_MODE_NEON */ #ifdef CONFIG_CPU_PM static int fpsimd_cpu_pm_notifier(struct notifier_block *self, unsigned long cmd, void *v) { switch (cmd) { case CPU_PM_ENTER: fpsimd_save_and_flush_cpu_state(); break; case CPU_PM_EXIT: break; case CPU_PM_ENTER_FAILED: default: return NOTIFY_DONE; } return NOTIFY_OK; } static struct notifier_block fpsimd_cpu_pm_notifier_block = { .notifier_call = fpsimd_cpu_pm_notifier, }; static void __init fpsimd_pm_init(void) { cpu_pm_register_notifier(&fpsimd_cpu_pm_notifier_block); } #else static inline void fpsimd_pm_init(void) { } #endif /* CONFIG_CPU_PM */ #ifdef CONFIG_HOTPLUG_CPU static int fpsimd_cpu_dead(unsigned int cpu) { per_cpu(fpsimd_last_state.st, cpu) = NULL; return 0; } static inline void fpsimd_hotplug_init(void) { cpuhp_setup_state_nocalls(CPUHP_ARM64_FPSIMD_DEAD, "arm64/fpsimd:dead", NULL, fpsimd_cpu_dead); } #else static inline void fpsimd_hotplug_init(void) { } #endif /* * FP/SIMD support code initialisation. */ static int __init fpsimd_init(void) { if (cpu_have_named_feature(FP)) { fpsimd_pm_init(); fpsimd_hotplug_init(); } else { pr_notice("Floating-point is not implemented\n"); } if (!cpu_have_named_feature(ASIMD)) pr_notice("Advanced SIMD is not implemented\n"); return sve_sysctl_init(); } core_initcall(fpsimd_init);
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