Release 4.18 arch/powerpc/mm/mmu_context.c
/*
* Common implementation of switch_mm_irqs_off
*
* Copyright IBM Corp. 2017
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
*/
#include <linux/mm.h>
#include <linux/cpu.h>
#include <linux/sched/mm.h>
#include <asm/mmu_context.h>
#if defined(CONFIG_PPC32)
static inline void switch_mm_pgdir(struct task_struct *tsk,
struct mm_struct *mm)
{
/* 32-bit keeps track of the current PGDIR in the thread struct */
tsk->thread.pgdir = mm->pgd;
}
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#elif defined(CONFIG_PPC_BOOK3E_64)
static inline void switch_mm_pgdir(struct task_struct *tsk,
struct mm_struct *mm)
{
/* 64-bit Book3E keeps track of current PGD in the PACA */
get_paca()->pgd = mm->pgd;
}
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#else
static inline void switch_mm_pgdir(struct task_struct *tsk,
struct mm_struct *mm) { }
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#endif
void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
struct task_struct *tsk)
{
bool new_on_cpu = false;
/* Mark this context has been used on the new CPU */
if (!cpumask_test_cpu(smp_processor_id(), mm_cpumask(next))) {
cpumask_set_cpu(smp_processor_id(), mm_cpumask(next));
inc_mm_active_cpus(next);
/*
* This full barrier orders the store to the cpumask above vs
* a subsequent operation which allows this CPU to begin loading
* translations for next.
*
* When using the radix MMU that operation is the load of the
* MMU context id, which is then moved to SPRN_PID.
*
* For the hash MMU it is either the first load from slb_cache
* in switch_slb(), and/or the store of paca->mm_ctx_id in
* copy_mm_to_paca().
*
* On the other side, the barrier is in mm/tlb-radix.c for
* radix which orders earlier stores to clear the PTEs vs
* the load of mm_cpumask. And pte_xchg which does the same
* thing for hash.
*
* This full barrier is needed by membarrier when switching
* between processes after store to rq->curr, before user-space
* memory accesses.
*/
smp_mb();
new_on_cpu = true;
}
/* Some subarchs need to track the PGD elsewhere */
switch_mm_pgdir(tsk, next);
/* Nothing else to do if we aren't actually switching */
if (prev == next)
return;
/*
* We must stop all altivec streams before changing the HW
* context
*/
if (cpu_has_feature(CPU_FTR_ALTIVEC))
asm volatile ("dssall");
if (new_on_cpu)
radix_kvm_prefetch_workaround(next);
else
membarrier_arch_switch_mm(prev, next, tsk);
/*
* The actual HW switching method differs between the various
* sub architectures. Out of line for now
*/
switch_mmu_context(prev, next, tsk);
}
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