From fa28ba21cec24d3fa1279bcae7e5d5ff6224635a Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Wed, 30 Jan 2008 13:34:11 +0100 Subject: x86: defer cr3 reload when doing pud_clear() PAE mode requires that we reload cr3 in order to guarantee that changes to the pgd will be noticed by the processor. This means that in principle pud_clear needs to reload cr3 every time. However, because reloading cr3 implies a tlb flush, we want to avoid it where possible. pud_clear() is only used in a couple of places: - in free_pmd_range(), when pulling down a range of process address space, and - huge_pmd_unshare() In both cases, the calling code will do a a tlb flush anyway, so there's no need to do it within pud_clear(). In free_pmd_range(), the pud_clear is immediately followed by pmd_free_tlb(); we can hook that to make the mmu_gather do an unconditional full flush to make sure cr3 gets reloaded. In huge_pmd_unshare, it is followed by flush_tlb_range, which always results in a full cr3-reload tlb flush. Signed-off-by: Jeremy Fitzhardinge Cc: Andi Kleen Cc: Linus Torvalds Cc: H. Peter Anvin Cc: William Irwin Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- include/asm-x86/pgalloc_32.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include/asm-x86/pgalloc_32.h') diff --git a/include/asm-x86/pgalloc_32.h b/include/asm-x86/pgalloc_32.h index 0caa37a9a25f..10c2b452e64c 100644 --- a/include/asm-x86/pgalloc_32.h +++ b/include/asm-x86/pgalloc_32.h @@ -74,6 +74,13 @@ static inline void pmd_free(pmd_t *pmd) static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd) { + /* This is called just after the pmd has been detached from + the pgd, which requires a full tlb flush to be recognized + by the CPU. Rather than incurring multiple tlb flushes + while the address space is being pulled down, make the tlb + gathering machinery do a full flush when we're done. */ + tlb->fullmm = 1; + paravirt_release_pd(__pa(pmd) >> PAGE_SHIFT); tlb_remove_page(tlb, virt_to_page(pmd)); } -- cgit v1.2.1