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arm64: mm: Make arch_faults_on_old_pte() check for migratability

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arch_faults_on_old_pte() relies on the calling context being
non-preemptible. CONFIG_PREEMPT_RT turns the PTE lock into a sleepable
spinlock, which doesn't disable preemption once acquired, triggering the
warning in arch_faults_on_old_pte().

It does however disable migration, ensuring the task remains on the same
CPU during the entirety of the critical section, making the read of
cpu_has_hw_af() safe and stable.

Make arch_faults_on_old_pte() check cant_migrate() instead of preemptible().

Cc: Valentin Schneider <vschneid@redhat.com>
Suggested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20220127192437.1192957-1-valentin.schneider@arm.com
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220505163207.85751-4-bigeasy@linutronix.de
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Valentin Schneider 2022-05-05 18:32:07 +02:00 committed by Catalin Marinas
parent b4d6bb38f9
commit c733812dd7
1 changed files with 2 additions and 1 deletions
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3
arch/arm64/include/asm/pgtable.h
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@ -1001,7 +1001,8 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
*/
static inline bool arch_faults_on_old_pte(void)
{
WARN_ON(preemptible());
/* The register read below requires a stable CPU to make any sense */
cant_migrate();
return !cpu_has_hw_af();
}