[PATCH v3 12/12] KVM: SEV: Mark vCPU has having guest-provided VMSA even if its invalid

[Sean Christopherson <seanjc@google.com>]

Track the guest as having a guest-provided VMSA as soon as control.vmsa_pa
is invalidated, instead of waiting to see if the guest-provided VMSA is
usable, so that KVM doesn't switch back to the original VMSA instead of
exiting to userspace (due to an invalid VMSA).  By the time a vCPU tries
to load a guest-provided VMSA, KVM has already communicated "success" for
AP creation, i.e. KVM has committed to using the guest-provided VMSA.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/svm/sev.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 2d2c159f20c2..ec426a5582aa 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -4005,23 +4005,6 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)
 	 */
 	vmcb_mark_all_dirty(svm->vmcb);
 
-	if (!VALID_PAGE(gpa))
-		return;
-
-	slot = gfn_to_memslot(vcpu->kvm, gfn);
-	if (!slot)
-		return;
-
-	mmu_seq = kvm->mmu_invalidate_seq;
-	smp_rmb();
-
-	/*
-	 * The new VMSA will be private memory guest memory, so retrieve the
-	 * PFN from the gmem backend.
-	 */
-	if (kvm_gmem_get_pfn(vcpu->kvm, slot, gfn, &pfn, &page, NULL))
-		return;
-
 	/*
 	 * From this point forward, the VMSA will always be a guest-mapped page
 	 * rather than the initial one allocated by KVM in svm->sev_es.vmsa. In
@@ -4033,6 +4016,23 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)
 	 */
 	svm->sev_es.snp_has_guest_vmsa = true;
 
+	if (!VALID_PAGE(gpa))
+		return;
+
+	slot = gfn_to_memslot(vcpu->kvm, gfn);
+	if (!slot)
+		return;
+
+	mmu_seq = kvm->mmu_invalidate_seq;
+	smp_rmb();
+
+	/*
+	 * The new VMSA will be private memory guest memory, so retrieve the
+	 * PFN from the gmem backend.
+	 */
+	if (kvm_gmem_get_pfn(vcpu->kvm, slot, gfn, &pfn, &page, NULL))
+		return;
+
 	read_lock(&kvm->mmu_lock);
 	/*
 	 * Save the guest-provided GPA.  If retry is needed, then KVM will try
-- 
2.55.0.rc0.799.gd6f94ed593-goog