x86: revert "defer cr3 reload when doing pud_clear()"

Revert "defer cr3 reload when doing pud_clear()" since I'm going to
replace it.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/mm/pgtable_32.c b/arch/x86/mm/pgtable_32.c
index f34e33d..c7db504 100644 (file)
--- a/arch/x86/mm/pgtable_32.c
+++ b/arch/x86/mm/pgtable_32.c
@@ -373,13 +373,6 @@ void __pte_free_tlb(struct mmu_gather *tlb, struct page *pte)
 
 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));
 }

diff --git a/include/asm-x86/pgtable-3level.h b/include/asm-x86/pgtable-3level.h
index a195c3e..ed4c6f0 100644 (file)
--- a/include/asm-x86/pgtable-3level.h
+++ b/include/asm-x86/pgtable-3level.h
@@ -96,23 +96,14 @@ static inline void pud_clear(pud_t *pudp)
        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.
+        * Pentium-II erratum A13: in PAE mode we explicitly have to flush
+        * the TLB via cr3 if the top-level pgd is changed...
         *
-        * 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.
-        *
-        * 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.
+        * XXX I don't think we need to worry about this here, since
+        * when clearing the pud, the calling code needs to flush the
+        * tlb anyway.  But do it now for safety's sake. - jsgf
         */
+       write_cr3(read_cr3());
 }
 
 #define pud_page(pud) \