[PATCH 17/24] KVM: SEV: Unmap and unpin the GHCB as needed on vCPU free

[Paolo Bonzini]

From: Sean Christopherson <seanjc@xxxxxxxxxx>

Unmap and unpin the GHCB as needed when freeing a vCPU.  If the VM is
destroyed after mapping+pinning the GHCB on #VMGEXIT, without re-running
the vCPU, KVM will effectively leak the GHCB and any mappings created for
the GHCB.

Fixes: 291bd20d5d88 ("KVM: SVM: Add initial support for a VMGEXIT VMEXIT")
Cc: stable@xxxxxxxxxxxxxxx
Tested-by: Michael Roth <michael.roth@xxxxxxx>
Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Reviewed-by: Michael Roth <michael.roth@xxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Message-ID: <20260501202250.2115252-18-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/svm/sev.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 11d46600cbdc..6c6a6d663e29 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3552,6 +3552,20 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
 	return 1;
 }
 
+static void __sev_es_unmap_ghcb(struct vcpu_svm *svm)
+{
+	if (svm->sev_es.ghcb_sa_free) {
+		kvfree(svm->sev_es.ghcb_sa);
+		svm->sev_es.ghcb_sa = NULL;
+		svm->sev_es.ghcb_sa_free = false;
+	}
+
+	if (svm->sev_es.ghcb) {
+		kvm_vcpu_unmap(&svm->vcpu, &svm->sev_es.ghcb_map);
+		svm->sev_es.ghcb = NULL;
+	}
+}
+
 void sev_es_unmap_ghcb(struct vcpu_svm *svm)
 {
 	/* Clear any indication that the vCPU is in a type of AP Reset Hold */
@@ -3570,18 +3584,11 @@ void sev_es_unmap_ghcb(struct vcpu_svm *svm)
 		svm->sev_es.ghcb_sa_sync = false;
 	}
 
-	if (svm->sev_es.ghcb_sa_free) {
-		kvfree(svm->sev_es.ghcb_sa);
-		svm->sev_es.ghcb_sa = NULL;
-		svm->sev_es.ghcb_sa_free = false;
-	}
-
 	trace_kvm_vmgexit_exit(svm->vcpu.vcpu_id, svm->sev_es.ghcb);
 
 	sev_es_sync_to_ghcb(svm);
 
-	kvm_vcpu_unmap(&svm->vcpu, &svm->sev_es.ghcb_map);
-	svm->sev_es.ghcb = NULL;
+	__sev_es_unmap_ghcb(svm);
 }
 
 void sev_free_vcpu(struct kvm_vcpu *vcpu)
@@ -3611,8 +3618,7 @@ void sev_free_vcpu(struct kvm_vcpu *vcpu)
 	__free_page(virt_to_page(svm->sev_es.vmsa));
 
 skip_vmsa_free:
-	if (svm->sev_es.ghcb_sa_free)
-		kvfree(svm->sev_es.ghcb_sa);
+	__sev_es_unmap_ghcb(svm);
 }
 
 int pre_sev_run(struct vcpu_svm *svm, int cpu)
-- 
2.54.0