Re: [PATCH v2 7/9] KVM: x86: allow L1 to not intercept triple fault

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On 03/11/2022 14:13, Maxim Levitsky wrote:
This is SVM correctness fix - although a sane L1 would intercept
SHUTDOWN event, it doesn't have to, so we have to honour this.

Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
---
  arch/x86/kvm/svm/nested.c |  6 ++++++
  arch/x86/kvm/vmx/nested.c |  1 +
  arch/x86/kvm/x86.c        | 11 ++++++-----
  3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index bcc4f6620f8aec..3aa9184d1e4ed7 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1092,6 +1092,12 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
static void nested_svm_triple_fault(struct kvm_vcpu *vcpu)
  {
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	if (!vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_SHUTDOWN))
+		return;
+
+	kvm_clear_request(KVM_REQ_TRIPLE_FAULT, vcpu);
  	nested_svm_simple_vmexit(to_svm(vcpu), SVM_EXIT_SHUTDOWN);

You could replace 'to_svm(vcpu)' with 'svm' here
But LGTM either way.

Reviewed-by: Liam Merwick <liam.merwick@xxxxxxxxxx>


  }
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 1ebe141a0a015f..7924dea9367813 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4855,6 +4855,7 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
static void nested_vmx_triple_fault(struct kvm_vcpu *vcpu)
  {
+	kvm_clear_request(KVM_REQ_TRIPLE_FAULT, vcpu);
  	nested_vmx_vmexit(vcpu, EXIT_REASON_TRIPLE_FAULT, 0, 0);
  }
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3fd900504e683b..f0a0102a78f5c3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9741,7 +9741,7 @@ static void update_cr8_intercept(struct kvm_vcpu *vcpu)
int kvm_check_nested_events(struct kvm_vcpu *vcpu)
  {
-	if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
+	if (kvm_test_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
  		kvm_x86_ops.nested_ops->triple_fault(vcpu);
  		return 1;
  	}
@@ -10255,15 +10255,16 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
  			r = 0;
  			goto out;
  		}
-		if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
-			if (is_guest_mode(vcpu)) {
+		if (kvm_test_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
+			if (is_guest_mode(vcpu))
  				kvm_x86_ops.nested_ops->triple_fault(vcpu);
-			} else {
+
+			if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
  				vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
  				vcpu->mmio_needed = 0;
  				r = 0;
-				goto out;
  			}
+			goto out;
  		}
  		if (kvm_check_request(KVM_REQ_APF_HALT, vcpu)) {
  			/* Page is swapped out. Do synthetic halt */




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