KVM: nSVM: fix few bugs in the vmcb02 caching logic

* Define and use an invalid GPA (all ones) for init value of last
  and current nested vmcb physical addresses.

* Reset the current vmcb12 gpa to the invalid value when leaving
  the nested mode, similar to what is done on nested vmexit.

* Reset	the last seen vmcb12 address when disabling the nested SVM,
  as it relies on vmcb02 fields which are freed at that point.

Fixes: 4995a3685f1b ("KVM: SVM: Use a separate vmcb for the nested L2 guest")

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210503125446.1353307-3-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 3321220f3deb..a88c64e004c3 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -872,6 +872,15 @@ void svm_free_nested(struct vcpu_svm *svm)
 	__free_page(virt_to_page(svm->nested.vmcb02.ptr));
 	svm->nested.vmcb02.ptr = NULL;
 
+	/*
+	 * When last_vmcb12_gpa matches the current vmcb12 gpa,
+	 * some vmcb12 fields are not loaded if they are marked clean
+	 * in the vmcb12, since in this case they are up to date already.
+	 *
+	 * When the vmcb02 is freed, this optimization becomes invalid.
+	 */
+	svm->nested.last_vmcb12_gpa = INVALID_GPA;
+
 	svm->nested.initialized = false;
 }
 
@@ -884,6 +893,8 @@ void svm_leave_nested(struct vcpu_svm *svm)
 
 	if (is_guest_mode(vcpu)) {
 		svm->nested.nested_run_pending = 0;
+		svm->nested.vmcb12_gpa = INVALID_GPA;
+
 		leave_guest_mode(vcpu);
 
 		svm_switch_vmcb(svm, &svm->vmcb01);