linux-kernel - [PATCH 2/2] KVM: SVM: Initialize vmsa_pa in VMCB to INVALID

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Message-ID: <20250602224459.41505-3-seanjc@google.com>
Date: Mon,  2 Jun 2025 15:44:59 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Alexander Potapenko <glider@...gle.com>, James Houghton <jthoughton@...gle.com>, 
	Peter Gonda <pgonda@...gle.com>, Tom Lendacky <thomas.lendacky@....com>
Subject: [PATCH 2/2] KVM: SVM: Initialize vmsa_pa in VMCB to INVALID_PAGE if
 VMSA page is NULL

When creating an SEV-ES vCPU for intra-host migration, set its vmsa_pa to
INVALID_PAGE to harden against doing VMRUN with a bogus VMSA (KVM checks
for a valid VMSA page in pre_sev_run()).

Cc: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/sev.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 93d899454535..5ebb265f2075 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -4471,8 +4471,12 @@ static void sev_es_init_vmcb(struct vcpu_svm *svm)
 	 * the VMSA will be NULL if this vCPU is the destination for intrahost
 	 * migration, and will be copied later.
 	 */
-	if (svm->sev_es.vmsa && !svm->sev_es.snp_has_guest_vmsa)
-		svm->vmcb->control.vmsa_pa = __pa(svm->sev_es.vmsa);
+	if (!svm->sev_es.snp_has_guest_vmsa) {
+		if (svm->sev_es.vmsa)
+			svm->vmcb->control.vmsa_pa = __pa(svm->sev_es.vmsa);
+		else
+			svm->vmcb->control.vmsa_pa = INVALID_PAGE;
+	}
 
 	/* Can't intercept CR register access, HV can't modify CR registers */
 	svm_clr_intercept(svm, INTERCEPT_CR0_READ);
-- 
2.49.0.1204.g71687c7c1d-goog