diff options
Diffstat (limited to 'arch/x86/include/asm/mmu_context.h')
| -rw-r--r-- | arch/x86/include/asm/mmu_context.h | 53 |
1 files changed, 46 insertions, 7 deletions
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index 40269a2bf6f..883f6b933fa 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -18,6 +18,21 @@ static inline void paravirt_activate_mm(struct mm_struct *prev, } #endif /* !CONFIG_PARAVIRT */ +#ifdef CONFIG_PERF_EVENTS +extern struct static_key rdpmc_always_available; + +static inline void load_mm_cr4(struct mm_struct *mm) +{ + if (static_key_true(&rdpmc_always_available) || + atomic_read(&mm->context.perf_rdpmc_allowed)) + cr4_set_bits(X86_CR4_PCE); + else + cr4_clear_bits(X86_CR4_PCE); +} +#else +static inline void load_mm_cr4(struct mm_struct *mm) {} +#endif + /* * Used for LDT copy/destruction. */ @@ -52,15 +67,20 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, /* Stop flush ipis for the previous mm */ cpumask_clear_cpu(cpu, mm_cpumask(prev)); + /* Load per-mm CR4 state */ + load_mm_cr4(next); + /* * Load the LDT, if the LDT is different. * - * It's possible leave_mm(prev) has been called. If so, - * then prev->context.ldt could be out of sync with the - * LDT descriptor or the LDT register. This can only happen - * if prev->context.ldt is non-null, since we never free - * an LDT. But LDTs can't be shared across mms, so - * prev->context.ldt won't be equal to next->context.ldt. + * It's possible that prev->context.ldt doesn't match + * the LDT register. This can happen if leave_mm(prev) + * was called and then modify_ldt changed + * prev->context.ldt but suppressed an IPI to this CPU. + * In this case, prev->context.ldt != NULL, because we + * never free an LDT while the mm still exists. That + * means that next->context.ldt != prev->context.ldt, + * because mms never share an LDT. */ if (unlikely(prev->context.ldt != next->context.ldt)) load_LDT_nolock(&next->context); @@ -85,6 +105,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, */ load_cr3(next->pgd); trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL); + load_mm_cr4(next); load_LDT_nolock(&next->context); } } @@ -130,7 +151,25 @@ static inline void arch_bprm_mm_init(struct mm_struct *mm, static inline void arch_unmap(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long start, unsigned long end) { - mpx_notify_unmap(mm, vma, start, end); + /* + * mpx_notify_unmap() goes and reads a rarely-hot + * cacheline in the mm_struct. That can be expensive + * enough to be seen in profiles. + * + * The mpx_notify_unmap() call and its contents have been + * observed to affect munmap() performance on hardware + * where MPX is not present. + * + * The unlikely() optimizes for the fast case: no MPX + * in the CPU, or no MPX use in the process. Even if + * we get this wrong (in the unlikely event that MPX + * is widely enabled on some system) the overhead of + * MPX itself (reading bounds tables) is expected to + * overwhelm the overhead of getting this unlikely() + * consistently wrong. + */ + if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX))) + mpx_notify_unmap(mm, vma, start, end); } #endif /* _ASM_X86_MMU_CONTEXT_H */ |