KVM: x86/mmu: Commit zap of remaining invalid pages when recovering lpages

commit e89505698c9f70125651060547da4ff5046124fc upstream.

Call kvm_mmu_commit_zap_page() after exiting the "prepare zap" loop in
kvm_recover_nx_lpages() to finish zapping pages in the unlikely event
that the loop exited due to lpage_disallowed_mmu_pages being empty.
Because the recovery thread drops mmu_lock() when rescheduling, it's
possible that lpage_disallowed_mmu_pages could be emptied by a different
thread without to_zap reaching zero despite to_zap being derived from
the number of disallowed lpages.

Fixes: 1aa9b9572b105 ("kvm: x86: mmu: Recovery of shattered NX large pages")
Cc: Junaid Shahid <junaids@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200923183735.584-2-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 73055b8e411f4b12a1bae6999a7ad36d50be1ae9..5cbc6591fa1d30fe9e94f5990e72c15c606c5315 100644 (file)
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -5321,6 +5321,7 @@ static void kvm_recover_nx_lpages(struct kvm *kvm)
                                cond_resched_lock(&kvm->mmu_lock);
                }
        }
+       kvm_mmu_commit_zap_page(kvm, &invalid_list);
 
        spin_unlock(&kvm->mmu_lock);
        srcu_read_unlock(&kvm->srcu, rcu_idx);