Re: [PATCH v13 34/48] arm64: RMI: support RSI_HOST_CALL

Suzuki K Poulose
2026-03-30T10:58:09Z

On 18/03/2026 15:53, Steven Price wrote:
> From: Joey Gouly <joey.gouly@arm.com>
>
> Forward RSI_HOST_CALLS to KVM's HVC handler.

Minor nit: Please could we add a line or two, explaining what
RSI_HOST_CALL is ? e.g.:

Realm's can talk to the hypervisor using the RSI_HOST_CALL, which
the RMM forwards to the KVM. Handle them as regular hypercalls.

Suzuki

>
> Signed-off-by: Joey Gouly <joey.gouly@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> ---
> Changes since v7:
> * Avoid turning a negative return from kvm_smccc_call_handler() into a
> error response to the guest. Instead propogate the error back to user
> space.
> Changes since v4:
> * Setting GPRS is now done by kvm_rec_enter() rather than
> rec_exit_host_call() (see previous patch - arm64: RME: Handle realm
> enter/exit). This fixes a bug where the registers set by user space
> were being ignored.
> ---
> arch/arm64/kvm/rmi-exit.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/arch/arm64/kvm/rmi-exit.c b/arch/arm64/kvm/rmi-exit.c
> index b4843f094615..7eff6967530c 100644
> --- a/arch/arm64/kvm/rmi-exit.c
> +++ b/arch/arm64/kvm/rmi-exit.c
> @@ -116,6 +116,19 @@ static int rec_exit_ripas_change(struct kvm_vcpu *vcpu)
> return -EFAULT;
> }
>
> +static int rec_exit_host_call(struct kvm_vcpu *vcpu)
> +{
> + int i;
> + struct realm_rec *rec = &vcpu->arch.rec;
> +
> + vcpu->stat.hvc_exit_stat++;
> +
> + for (i = 0; i < REC_RUN_GPRS; i++)
> + vcpu_set_reg(vcpu, i, rec->run->exit.gprs[i]);
> +
> + return kvm_smccc_call_handler(vcpu);
> +}
> +
> static void update_arch_timer_irq_lines(struct kvm_vcpu *vcpu)
> {
> struct realm_rec *rec = &vcpu->arch.rec;
> @@ -183,6 +196,8 @@ int handle_rec_exit(struct kvm_vcpu *vcpu, int rec_run_ret)
> return rec_exit_psci(vcpu);
> case RMI_EXIT_RIPAS_CHANGE:
> return rec_exit_ripas_change(vcpu);
> + case RMI_EXIT_HOST_CALL:
> + return rec_exit_host_call(vcpu);
> }

Probably we should move the RMI_EXIT_HOST_CALL case addition in
kvm_rec_pre_enter() to this hunk to keep all in one place ?

Otherwise, looks good to me.

Suzuki

>
> kvm_pr_unimpl("Unsupported exit reason: %u\n",