From 5e4bf1a55da976a5ed60901bb8801f1024ef9774 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 20 Nov 2012 13:02:51 +0100 Subject: [PATCH] x86/mm: Don't flush the TLB on #WP pmd fixups If we have a write protection #PF and fix up the pmd then the hugetlb code [the only user of pmdp_set_access_flags], in its do_huge_pmd_wp_page() page fault resolution function calls pmdp_set_access_flags() to mark the pmd permissive again, and flushes the TLB. This TLB flush is unnecessary: a flush on #PF is guaranteed on most (all?) x86 CPUs, and even in the worst-case we'll generate a spurious fault. So remove it. Cc: Linus Torvalds Cc: Andrew Morton Cc: Peter Zijlstra Cc: Paul Turner Cc: Lee Schermerhorn Cc: Andrea Arcangeli Cc: Rik van Riel Cc: Johannes Weiner Cc: Christoph Lameter Cc: Mel Gorman Cc: Hugh Dickins Link: http://lkml.kernel.org/r/20121120120251.GA15742@gmail.com Signed-off-by: Ingo Molnar --- arch/x86/mm/pgtable.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index 8573b83a63d0..8a828d773e58 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -328,7 +328,12 @@ int pmdp_set_access_flags(struct vm_area_struct *vma, if (changed && dirty) { *pmdp = entry; pmd_update_defer(vma->vm_mm, address, pmdp); - flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE); + /* + * We had a write-protection fault here and changed the pmd + * to to more permissive. No need to flush the TLB for that, + * #PF is architecturally guaranteed to do that and in the + * worst-case we'll generate a spurious fault. + */ } return changed; -- 2.20.1