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Commit 0e7bc4b9 authored by Avi Kivity's avatar Avi Kivity Committed by Linus Torvalds
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[PATCH] KVM: MMU: Handle misaligned accesses to write protected guest page tables 



A misaligned access affects two shadow ptes instead of just one.

Since a misaligned access is unlikely to occur on a real page table, just zap
the page out of existence, avoiding further trouble.

Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 73f7198e

drivers/kvm/mmu.c

+17 −2
Original line number Diff line number Diff line
@@ -954,21 +954,36 @@ void kvm_mmu_pre_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes) 
	gfn_t gfn = gpa >> PAGE_SHIFT;

	struct kvm_mmu_page *page;

	struct kvm_mmu_page *child;

	struct hlist_node *node;

	struct hlist_node *node, *n;

	struct hlist_head *bucket;

	unsigned index;

	u64 *spte;

	u64 pte;

	unsigned offset = offset_in_page(gpa);

	unsigned pte_size;

	unsigned page_offset;

	unsigned misaligned;

	int level;



	pgprintk("%s: gpa %llx bytes %d\n", __FUNCTION__, gpa, bytes);

	index = kvm_page_table_hashfn(gfn) % KVM_NUM_MMU_PAGES;

	bucket = &vcpu->kvm->mmu_page_hash[index];

	hlist_for_each_entry(page, node, bucket, hash_link) {

	hlist_for_each_entry_safe(page, node, n, bucket, hash_link) {

		if (page->gfn != gfn || page->role.metaphysical)

			continue;

		pte_size = page->role.glevels == PT32_ROOT_LEVEL ? 4 : 8;

		misaligned = (offset ^ (offset + bytes - 1)) & ~(pte_size - 1);

		if (misaligned) {

			/*

			 * Misaligned accesses are too much trouble to fix

			 * up; also, they usually indicate a page is not used

			 * as a page table.

			 */

			pgprintk("misaligned: gpa %llx bytes %d role %x\n",

				 gpa, bytes, page->role.word);

			kvm_mmu_zap_page(vcpu, page);

			continue;

		}

		page_offset = offset;

		level = page->role.level;

		if (page->role.glevels == PT32_ROOT_LEVEL) {