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Diffstat (limited to 'include/asm-x86/pgtable-3level.h')
-rw-r--r--include/asm-x86/pgtable-3level.h26
1 files changed, 11 insertions, 15 deletions
diff --git a/include/asm-x86/pgtable-3level.h b/include/asm-x86/pgtable-3level.h
index a195c3e757b..1d763eec740 100644
--- a/include/asm-x86/pgtable-3level.h
+++ b/include/asm-x86/pgtable-3level.h
@@ -93,26 +93,22 @@ 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));
/*
- * In principle we need to do a cr3 reload here to make sure
- * the processor recognizes the changed pgd. In practice, all
- * the places where pud_clear() gets called are followed by
- * full tlb flushes anyway, so we can defer the cost here.
- *
- * Specifically:
- *
- * mm/memory.c:free_pmd_range() - immediately after the
- * pud_clear() it does a pmd_free_tlb(). We change the
- * mmu_gather structure to do a full tlb flush (which has the
- * effect of reloading cr3) when the pagetable free is
- * complete.
+ * According to Intel App note "TLBs, Paging-Structure Caches,
+ * and Their Invalidation", April 2007, document 317080-001,
+ * section 8.1: in PAE mode we explicitly have to flush the
+ * TLB via cr3 if the top-level pgd is changed...
*
- * arch/x86/mm/hugetlbpage.c:huge_pmd_unshare() - the call to
- * this is followed by a flush_tlb_range, which on x86 does a
- * full tlb flush.
+ * Make sure the pud entry we're updating is within the
+ * current pgd to avoid unnecessary TLB flushes.
*/
+ pgd = read_cr3();
+ if (__pa(pudp) >= pgd && __pa(pudp) < (pgd + sizeof(pgd_t)*PTRS_PER_PGD))
+ write_cr3(pgd);
}
#define pud_page(pud) \