On Wed, Jul 05, 2017 at 03:31:03AM -0700, tip-bot for Andy Lutomirski wrote:
> @@ -132,6 +135,9 @@ static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
> static inline int init_new_context(struct task_struct *tsk,
> struct mm_struct *mm)
> {
> + mm->context.ctx_id = atomic64_inc_return(&last_mm_ctx_id);
You could use atomic64_inc_return_relaxed() here; but since its x86
specific there is no difference.
> + atomic64_set(&mm->context.tlb_gen, 0);
> +
> #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
> if (cpu_feature_enabled(X86_FEATURE_OSPKE)) {
> /* pkey 0 is the default and always allocated */
> diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
> index 50ea348..ad21353 100644
> --- a/arch/x86/include/asm/tlbflush.h
> +++ b/arch/x86/include/asm/tlbflush.h
> @@ -57,6 +57,23 @@ static inline void invpcid_flush_all_nonglobals(void)
> __invpcid(0, 0, INVPCID_TYPE_ALL_NON_GLOBAL);
> }
>
> +static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
> +{
> + u64 new_tlb_gen;
> +
> + /*
> + * Bump the generation count. This also serves as a full barrier
> + * that synchronizes with switch_mm(): callers are required to order
> + * their read of mm_cpumask after their writes to the paging
> + * structures.
> + */
> + smp_mb__before_atomic();
> + new_tlb_gen = atomic64_inc_return(&mm->context.tlb_gen);
> + smp_mb__after_atomic();
that's wrong... smp_mb__{before,after}_atomic() are entirely superfluous
here:
- they're no-ops on x86
- atomic_*_return() is already fully serializing
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