From: Jeremy Fitzhardinge Date: Wed, 30 Jan 2008 12:34:11 +0000 (+0100) Subject: x86: defer cr3 reload when doing pud_clear() X-Git-Tag: v2.6.25-rc1~1143^2~5 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fa28ba21cec24d3fa1279bcae7e5d5ff6224635a;p=pandora-kernel.git 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 --- Reading git-diff-tree failed