[PATCH v4 24/28] KVM: arm64: nv: Expand ERET trap forwarding to handle FGT

[Marc Zyngier]

We already handle ERET being trapped from a L1 guest in hyp context.
However, with FGT, we can also have ERET being trapped from L2, and
this needs to be reinjected into L1.

Add the required exception routing.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/handle_exit.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 3b86d534b995..617ae6dea5d5 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -222,7 +222,22 @@ static int kvm_handle_eret(struct kvm_vcpu *vcpu)
 	if (kvm_vcpu_get_esr(vcpu) & ESR_ELx_ERET_ISS_ERET)
 		return kvm_handle_ptrauth(vcpu);
 
-	kvm_emulate_nested_eret(vcpu);
+	/*
+	 * If we got here, two possibilities:
+	 *
+	 * - the guest is in EL2, and we need to fully emulate ERET
+	 *
+	 * - the guest is in EL1, and we need to reinject the
+         *   exception into the L1 hypervisor.
+	 *
+	 * If KVM ever traps ERET for its own use, we'll have to
+	 * revisit this.
+	 */
+	if (is_hyp_ctxt(vcpu))
+		kvm_emulate_nested_eret(vcpu);
+	else
+		kvm_inject_nested_sync(vcpu, kvm_vcpu_get_esr(vcpu));
+
 	return 1;
 }
 
-- 
2.34.1