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@amd.com>
Link: https://lore.kernel.org/r/20250227012541.3234589-11-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index f1139e2251b678256fd510ac25b4216bdb39fdf4..ea50f44a223949ffb87019a17f169e980f828d9e 100644 (file)
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3880,6 +3880,7 @@ 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)
@@ -3910,8 +3911,6 @@ void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu)
        vcpu->arch.pv.pv_unhalted = false;
        vcpu->arch.mp_state = 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