[PATCH v6 27/43] arm64: rme: support RSI_HOST_CALL

[Gavin Shan]

On 12/13/24 1:55 AM, Steven Price wrote:
> From: Joey Gouly <joey.gouly at arm.com>
> 
> Forward RSI_HOST_CALLS to KVM's HVC handler.
> 
> Signed-off-by: Joey Gouly <joey.gouly at arm.com>
> Signed-off-by: Steven Price <steven.price at arm.com>
> ---
> 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/rme-exit.c | 22 ++++++++++++++++++++++
>   1 file changed, 22 insertions(+)
> 
> diff --git a/arch/arm64/kvm/rme-exit.c b/arch/arm64/kvm/rme-exit.c
> index 8f0f9ab57f28..b2a367474d74 100644
> --- a/arch/arm64/kvm/rme-exit.c
> +++ b/arch/arm64/kvm/rme-exit.c
> @@ -103,6 +103,26 @@ static int rec_exit_ripas_change(struct kvm_vcpu *vcpu)
>   	return 0;
>   }
>   
> +static int rec_exit_host_call(struct kvm_vcpu *vcpu)
> +{
> +	int ret, 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]);
> +
> +	ret = kvm_smccc_call_handler(vcpu);
> +
> +	if (ret < 0) {
> +		vcpu_set_reg(vcpu, 0, ~0UL);
> +		ret = 1;
> +	}
> +
> +	return ret;
> +}
> +

It seems that the return value from kvm_smccc_call() won't be negative. Besides,
the host call requests are currently handled by kvm_psci_call(), which isn't
what we want. So I think a new helper is needed and called in kvm_smccc_call_handler().
The new helper simply push the error (NOT_SUPPORTED) to x0. Otherwise, a unexpected
return value will be seen by guest.

handle_rec_exit
   rec_exit_host_call
     kvm_smccc_call_handler

>   static void update_arch_timer_irq_lines(struct kvm_vcpu *vcpu)
>   {
>   	struct realm_rec *rec = &vcpu->arch.rec;
> @@ -164,6 +184,8 @@ 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);
>   	}
>   
>   	kvm_pr_unimpl("Unsupported exit reason: %u\n",

Thanks,
Gavin