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

[Jing Zhang]

Hi Marc,

On Tue, Aug 15, 2023 at 11:47 AM Marc Zyngier <maz at kernel.org> wrote:
>
> 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
>

Reviewed-by: Jing Zhang <jingzhangos at google.com>

Jing