Commit f95eec9b authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: Don't put invalid SPs back on the list of active pages 



Delete a shadow page from the invalidation list instead of throwing it
back on the list of active pages when it's a root shadow page with
active users.  Invalid active root pages will be explicitly freed by
mmu_free_root_page() when the root_count hits zero, i.e. they don't need
to be put on the active list to avoid leakage.

Use sp->role.invalid to detect that a shadow page has already been
zapped, i.e. is not on a list.

WARN if an invalid page is encountered when zapping pages, as it should
now be impossible.

Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200623193542.7554-2-sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent fb58a9c3

arch/x86/kvm/mmu/mmu.c

+20 −8
Original line number Diff line number Diff line
@@ -2748,10 +2748,23 @@ static bool __kvm_mmu_prepare_zap_page(struct kvm *kvm, 
	if (!sp->root_count) {

		/* Count self */

		(*nr_zapped)++;



		/*

		 * Already invalid pages (previously active roots) are not on

		 * the active page list.  See list_del() in the "else" case of

		 * !sp->root_count.

		 */

		if (sp->role.invalid)

			list_add(&sp->link, invalid_list);

		else

			list_move(&sp->link, invalid_list);

		kvm_mod_used_mmu_pages(kvm, -1);

	} else {

		list_move(&sp->link, &kvm->arch.active_mmu_pages);

		/*

		 * Remove the active root from the active page list, the root

		 * will be explicitly freed when the root_count hits zero.

		 */

		list_del(&sp->link);



		/*

		 * Obsolete pages cannot be used on any vCPUs, see the comment
@@ -5718,12 +5731,11 @@ static void kvm_zap_obsolete_pages(struct kvm *kvm) 
			break;



		/*

		 * Skip invalid pages with a non-zero root count, zapping pages

		 * with a non-zero root count will never succeed, i.e. the page

		 * will get thrown back on active_mmu_pages and we'll get stuck

		 * in an infinite loop.

		 * Invalid pages should never land back on the list of active

		 * pages.  Skip the bogus page, otherwise we'll get stuck in an

		 * infinite loop if the page gets put back on the list (again).

		 */

		if (sp->role.invalid && sp->root_count)

		if (WARN_ON(sp->role.invalid))

			continue;



		/*
@@ -6001,7 +6013,7 @@ void kvm_mmu_zap_all(struct kvm *kvm) 
	spin_lock(&kvm->mmu_lock);

restart:

	list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {

		if (sp->role.invalid && sp->root_count)

		if (WARN_ON(sp->role.invalid))

			continue;

		if (__kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list, &ign))

			goto restart;