From f95eec9bed76d42194c23153cb1cc8f186bf91cb Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 23 Jun 2020 12:35:39 -0700 Subject: 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: Sean Christopherson Message-Id: <20200623193542.7554-2-sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/mmu.c | 28 ++++++++++++++++++++-------- 1 file changed, 20 insertions(+), 8 deletions(-) (limited to 'arch/x86/kvm/mmu') diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 1b2988a9f0c6..14c16773e830 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2748,10 +2748,23 @@ static bool __kvm_mmu_prepare_zap_page(struct kvm *kvm, if (!sp->root_count) { /* Count self */ (*nr_zapped)++; - list_move(&sp->link, invalid_list); + + /* + * 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 @@ restart: 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; -- cgit v1.2.3