From 4981d01eada5354d81c8929d5b2836829ba3df7b Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Wed, 16 Mar 2011 11:37:29 +0800 Subject: [PATCH] x86: Flush TLB if PGD entry is changed in i386 PAE mode According to intel CPU manual, every time PGD entry is changed in i386 PAE mode, we need do a full TLB flush. Current code follows this and there is comment for this too in the code. But current code misses the multi-threaded case. A changed page table might be used by several CPUs, every such CPU should flush TLB. Usually this isn't a problem, because we prepopulate all PGD entries at process fork. But when the process does munmap and follows new mmap, this issue will be triggered. When it happens, some CPUs keep doing page faults: http://marc.info/?l=linux-kernel&m=129915020508238&w=2 Reported-by: Yasunori Goto Tested-by: Yasunori Goto Reviewed-by: Rik van Riel Signed-off-by: Shaohua Li Cc: Mallick Asit K Cc: Linus Torvalds Cc: Andrew Morton Cc: linux-mm Cc: stable LKML-Reference: <1300246649.2337.95.camel@sli10-conroe> Signed-off-by: Ingo Molnar --- arch/x86/include/asm/pgtable-3level.h | 11 +++-------- arch/x86/mm/pgtable.c | 3 +-- 2 files changed, 4 insertions(+), 10 deletions(-) diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h index 94b979d1b58d..effff47a3c82 100644 --- a/arch/x86/include/asm/pgtable-3level.h +++ b/arch/x86/include/asm/pgtable-3level.h @@ -69,8 +69,6 @@ static inline void native_pmd_clear(pmd_t *pmd) static inline void pud_clear(pud_t *pudp) { - unsigned long pgd; - set_pud(pudp, __pud(0)); /* @@ -79,13 +77,10 @@ static inline void pud_clear(pud_t *pudp) * section 8.1: in PAE mode we explicitly have to flush the * TLB via cr3 if the top-level pgd is changed... * - * Make sure the pud entry we're updating is within the - * current pgd to avoid unnecessary TLB flushes. + * Currently all places where pud_clear() is called either have + * flush_tlb_mm() followed or don't need TLB flush (x86_64 code or + * pud_clear_bad()), so we don't need TLB flush here. */ - pgd = read_cr3(); - if (__pa(pudp) >= pgd && __pa(pudp) < - (pgd + sizeof(pgd_t)*PTRS_PER_PGD)) - write_cr3(pgd); } #ifdef CONFIG_SMP diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index 0113d19c8aa6..8573b83a63d0 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -168,8 +168,7 @@ void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd) * section 8.1: in PAE mode we explicitly have to flush the * TLB via cr3 if the top-level pgd is changed... */ - if (mm == current->active_mm) - write_cr3(read_cr3()); + flush_tlb_mm(mm); } #else /* !CONFIG_X86_PAE */ -- 2.20.1