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

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));

}

	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) \