From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] KVM: x86/mmu: Don't put invalid SPs back on the list of active pages
Date: Mon, 22 Jun 2020 12:18:50 -0700 [thread overview]
Message-ID: <20200622191850.8529-1-sean.j.christopherson@intel.com> (raw)
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 <sean.j.christopherson@intel.com>
---
arch/x86/kvm/mmu/mmu.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index fdd05c233308..fa5bd3f987dd 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2757,10 +2757,13 @@ static bool __kvm_mmu_prepare_zap_page(struct kvm *kvm,
if (!sp->root_count) {
/* Count self */
(*nr_zapped)++;
- list_move(&sp->link, invalid_list);
+ 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);
+ list_del(&sp->link);
/*
* Obsolete pages cannot be used on any vCPUs, see the comment
@@ -5732,12 +5735,11 @@ 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;
/*
@@ -6015,7 +6017,7 @@ 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;
--
2.26.0
next reply other threads:[~2020-06-22 19:18 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-22 19:18 Sean Christopherson [this message]
2020-06-23 0:23 ` [PATCH] KVM: x86/mmu: Don't put invalid SPs back on the list of active pages Paolo Bonzini
2020-06-23 1:15 ` Sean Christopherson
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