diff options
Diffstat (limited to 'arch/powerpc/include/asm/book3s/64/radix.h')
| -rw-r--r-- | arch/powerpc/include/asm/book3s/64/radix.h | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h index 01f6c2ca7ecd..9c567d243f61 100644 --- a/arch/powerpc/include/asm/book3s/64/radix.h +++ b/arch/powerpc/include/asm/book3s/64/radix.h @@ -202,7 +202,24 @@ static inline void radix__set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte, int percpu) { *ptep = pte; - asm volatile("ptesync" : : : "memory"); + + /* + * The architecture suggests a ptesync after setting the pte, which + * orders the store that updates the pte with subsequent page table + * walk accesses which may load the pte. Without this it may be + * possible for a subsequent access to result in spurious fault. + * + * This is not necessary for correctness, because a spurious fault + * is tolerated by the page fault handler, and this store will + * eventually be seen. In testing, there was no noticable increase + * in user faults on POWER9. Avoiding ptesync here is a significant + * win for things like fork. If a future microarchitecture benefits + * from ptesync, it should probably go into update_mmu_cache, rather + * than set_pte_at (which is used to set ptes unrelated to faults). + * + * Spurious faults to vmalloc region are not tolerated, so there is + * a ptesync in flush_cache_vmap. + */ } static inline int radix__pmd_bad(pmd_t pmd) |