Re: [PATCH v20 07/14] KVM: arm64: Forward GCS exceptions to nested guests

For nested guests where HFGITR_EL2.nGCSSTR_EL1 is clear or when there are
L2 GCS data check exceptions we need to forward the exception to the guest.
Add handling to do so.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/kvm/handle_exit.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index db37678dcb05..a8198e96fcb4 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c

@@ -304,12 +304,24 @@ static int handle_svc(struct kvm_vcpu *vcpu)
 	return 1;
 }
 
+/*
+ * We might get GCS exceptions that need to be forwarded to the
+ * hypervisor when a nested guest has HFGITR_EL2.nGCSSTR_EL1 clear, or
+ * for a GCS data check exception for a L2 guest.
+ */
 static int kvm_handle_gcs(struct kvm_vcpu *vcpu)
 {
-	/* We don't expect GCS, so treat it with contempt */
-	if (kvm_has_feat(vcpu->kvm, ID_AA64PFR1_EL1, GCS, IMP))
-		WARN_ON_ONCE(1);
+	if (!kvm_has_gcs(vcpu->kvm)) {
+		kvm_inject_undefined(vcpu);
+		return 1;
+	}
 
+	if (vcpu_has_nv(vcpu)) {
+		kvm_inject_nested_sync(vcpu, kvm_vcpu_get_esr(vcpu));
+		return 1;
+	}
+
+	WARN_ON_ONCE(1);
 	kvm_inject_undefined(vcpu);
 	return 1;
 }