Commit d05fdf31 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Ingo Molnar
Browse files

xen: make sure stray alias mappings are gone before pinning 



Xen requires that all mappings of pagetable pages are read-only, so
that they can't be updated illegally.  As a result, if a page is being
turned into a pagetable page, we need to make sure all its mappings
are RO.

If the page had been used for ioremap or vmalloc, it may still have
left over mappings as a result of not having been lazily unmapped.
This change makes sure we explicitly mop them all up before pinning
the page.

Unlike aliases created by kmap, the there can be vmalloc aliases even
for non-high pages, so we must do the flush unconditionally.

Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Linux Memory Management List <linux-mm@kvack.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 9b463334

arch/x86/xen/enlighten.c

+3 −2
Original line number Original line Diff line number Diff line
@@ -863,15 +863,16 @@ static void xen_alloc_ptpage(struct mm_struct *mm, unsigned long pfn, unsigned l 
	if (PagePinned(virt_to_page(mm->pgd))) {

	if (PagePinned(virt_to_page(mm->pgd))) {

		SetPagePinned(page);

		SetPagePinned(page);





		vm_unmap_aliases();

		if (!PageHighMem(page)) {

		if (!PageHighMem(page)) {

			make_lowmem_page_readonly(__va(PFN_PHYS((unsigned long)pfn)));

			make_lowmem_page_readonly(__va(PFN_PHYS((unsigned long)pfn)));

			if (level == PT_PTE && USE_SPLIT_PTLOCKS)

			if (level == PT_PTE && USE_SPLIT_PTLOCKS)

				pin_pagetable_pfn(MMUEXT_PIN_L1_TABLE, pfn);

				pin_pagetable_pfn(MMUEXT_PIN_L1_TABLE, pfn);

		} else

		} else {

			/* make sure there are no stray mappings of

			/* make sure there are no stray mappings of

			   this page */

			   this page */

			kmap_flush_unused();

			kmap_flush_unused();

			vm_unmap_aliases();

		}

	}

	}

}

}

arch/x86/xen/mmu.c

+6 −3
Original line number Original line Diff line number Diff line
@@ -850,13 +850,16 @@ static int xen_pin_page(struct mm_struct *mm, struct page *page, 
   read-only, and can be pinned. */

   read-only, and can be pinned. */

static void __xen_pgd_pin(struct mm_struct *mm, pgd_t *pgd)

static void __xen_pgd_pin(struct mm_struct *mm, pgd_t *pgd)

{

{

	vm_unmap_aliases();



	xen_mc_batch();

	xen_mc_batch();





	 if (xen_pgd_walk(mm, xen_pin_page, USER_LIMIT)) {

	 if (xen_pgd_walk(mm, xen_pin_page, USER_LIMIT)) {

		/* re-enable interrupts for kmap_flush_unused */

		/* re-enable interrupts for flushing */

		xen_mc_issue(0);

		xen_mc_issue(0);



		kmap_flush_unused();

		kmap_flush_unused();

		vm_unmap_aliases();



		xen_mc_batch();

		xen_mc_batch();

	}

	}

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