linux-kernel - [PATCH 10/10] KVM: SVM: Invalidate "next" SNP VMSA GPA even on failure

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Message-ID: <20250219012705.1495231-11-seanjc@google.com>
Date: Tue, 18 Feb 2025 17:27:05 -0800
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, 
	Naveen N Rao <naveen@...nel.org>, Kim Phillips <kim.phillips@....com>, 
	Tom Lendacky <thomas.lendacky@....com>, Alexey Kardashevskiy <aik@....com>
Subject: [PATCH 10/10] KVM: SVM: Invalidate "next" SNP VMSA GPA even on failure

When processing an SNP AP Creation event, invalidate the "next" VMSA GPA
even if acquiring the page/pfn for the new VMSA fails.  In practice, the
next GPA will never be used regardless of whether or not its invalidated,
as the entire flow is guarded by snp_ap_waiting_for_reset, and said guard
and snp_vmsa_gpa are always written as a pair.  But that's really hard to
see in the code.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/sev.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 15c324b61b24..7345cac6f93a 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3877,6 +3877,7 @@ void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu)
 		return;
 
 	gfn = gpa_to_gfn(svm->sev_es.snp_vmsa_gpa);
+	svm->sev_es.snp_vmsa_gpa = INVALID_PAGE;
 
 	slot = gfn_to_memslot(vcpu->kvm, gfn);
 	if (!slot)
@@ -3906,8 +3907,6 @@ void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu)
 	/* Mark the vCPU as runnable */
 	kvm_set_mp_state(vcpu, KVM_MP_STATE_RUNNABLE);
 
-	svm->sev_es.snp_vmsa_gpa = INVALID_PAGE;
-
 	/*
 	 * gmem pages aren't currently migratable, but if this ever changes
 	 * then care should be taken to ensure svm->sev_es.vmsa is pinned
-- 
2.48.1.601.g30ceb7b040-goog