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

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@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