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>

2 files changed, 6 insertions, 22 deletions

diff --git a/arch/x86/mm/pgtable_32.c b/arch/x86/mm/pgtable_32.c
index f34e33d18443..c7db504be1ea 100644
--- 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 a195c3e757b9..ed4c6f0e57ec 100644
--- 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) \