linux-kernel - [PATCH v2 10/10] KVM: SVM: Invalidate "next" SNP VMSA GPA even on failure

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Message-ID: <20250227012541.3234589-11-seanjc@google.com>
Date: Wed, 26 Feb 2025 17:25:41 -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>, 
	Pankaj Gupta <pankaj.gupta@....com>
Subject: [PATCH v2 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.

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
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 3f85bd1cac37..de153a19fa6c 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3875,6 +3875,7 @@ 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)
@@ -3904,8 +3905,6 @@ 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
-- 
2.48.1.711.g2feabab25a-goog