linux-kernel - [RFC PATCH v2 09/17] KVM: SVM: Do not intercept exceptions for Secure AVIC guests

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Message-ID: <20250923050317.205482-10-Neeraj.Upadhyay@amd.com>
Date: Tue, 23 Sep 2025 10:33:09 +0530
From: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
To: <kvm@...r.kernel.org>, <seanjc@...gle.com>, <pbonzini@...hat.com>
CC: <linux-kernel@...r.kernel.org>, <Thomas.Lendacky@....com>,
	<nikunj@....com>, <Santosh.Shukla@....com>, <Vasant.Hegde@....com>,
	<Suravee.Suthikulpanit@....com>, <bp@...en8.de>, <David.Kaplan@....com>,
	<huibo.wang@....com>, <naveen.rao@....com>, <tiala@...rosoft.com>
Subject: [RFC PATCH v2 09/17] KVM: SVM: Do not intercept exceptions for Secure AVIC guests

Exceptions cannot be explicitly injected from the hypervisor to
Secure AVIC enabled guests. So, KVM cannot inject exceptions into
a Secure AVIC guest. If KVM were to intercept an exception (e.g., #PF
or #GP), it would be unable to deliver it back to the guest, effectively
dropping the event and leading to guest misbehavior or hangs. So,
clear exception intercepts so that all exceptions are handled directly by
the guest without KVM intervention.

Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
---
 arch/x86/kvm/svm/sev.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index a64fcc7637c7..837ab55a3330 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -4761,8 +4761,17 @@ static void sev_es_init_vmcb(struct vcpu_svm *svm)
 	/* Can't intercept XSETBV, HV can't modify XCR0 directly */
 	svm_clr_intercept(svm, INTERCEPT_XSETBV);
 
-	if (sev_savic_active(vcpu->kvm))
+	if (sev_savic_active(vcpu->kvm)) {
 		svm_set_intercept_for_msr(vcpu, MSR_AMD64_SAVIC_CONTROL, MSR_TYPE_RW, false);
+
+		/* Clear all exception intercepts. */
+		clr_exception_intercept(svm, PF_VECTOR);
+		clr_exception_intercept(svm, UD_VECTOR);
+		clr_exception_intercept(svm, MC_VECTOR);
+		clr_exception_intercept(svm, AC_VECTOR);
+		clr_exception_intercept(svm, DB_VECTOR);
+		clr_exception_intercept(svm, GP_VECTOR);
+	}
 }
 
 void sev_init_vmcb(struct vcpu_svm *svm)
-- 
2.34.1