linux-kernel - [PATCH 7/9] KVM: x86: allow L1 to not intercept triple fault

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Date:   Thu,  3 Nov 2022 15:57:34 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Shuah Khan <shuah@...nel.org>,
        Yang Zhong <yang.zhong@...el.com>,
        Wei Wang <wei.w.wang@...el.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Chenyi Qiang <chenyi.qiang@...el.com>,
        Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org,
        x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        David Matlack <dmatlack@...gle.com>,
        Peter Xu <peterx@...hat.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-kselftest@...r.kernel.org
Subject: [PATCH 7/9] KVM: x86: allow L1 to not intercept triple fault

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@...hat.com>
---
 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);
 }
 
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 */
-- 
2.34.3