On 04/03/2025 06:01, Gavin Shan wrote:
> On 2/14/25 2:14 AM, Steven Price wrote:
>> From: Joey Gouly <joey.gouly@xxxxxxx>
>>
>> Forward RSI_HOST_CALLS to KVM's HVC handler.
>>
>> Signed-off-by: Joey Gouly <joey.gouly@xxxxxxx>
>> Signed-off-by: Steven Price <steven.price@xxxxxxx>
>> ---
>> 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 c785005f821f..4f7602aa3c6c 100644
>> --- a/arch/arm64/kvm/rme-exit.c
>> +++ b/arch/arm64/kvm/rme-exit.c
>> @@ -107,6 +107,26 @@ static int rec_exit_ripas_change(struct kvm_vcpu
>> *vcpu)
>> return -EFAULT;
>> }
>> +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;
>> +}
>> +
>
> I don't understand how a negative error can be returned from
> kvm_smccc_call_handler().
I don't believe it really can. However kvm_smccc_call_handler() calls
kvm_psci_call() and that has a documentation block which states:
* This function returns: > 0 (success), 0 (success but exit to user
* space), and < 0 (errors)
*
* Errors:
* -EINVAL: Unrecognized PSCI function
But I can't actually see code which returns the negative value...
> Besides, SMCCC_RET_NOT_SUPPORTED has been set to GPR[0 - 3] if the
> request can't be
> supported. Why we need to set GPR[0] to ~0UL, which corresponds to
> SMCCC_RET_NOT_SUPPORTED
> if I'm correct. I guess change log or a comment to explain the questions
> would be
> nice.
I'll add a comment explaining we don't expect negative codes. And I'll
expand ~0UL to SMCCC_RET_NOT_SUPPORTED which is what it should be.
Thanks,
Steve
>> static void update_arch_timer_irq_lines(struct kvm_vcpu *vcpu)
>> {
>> struct realm_rec *rec = &vcpu->arch.rec;
>> @@ -168,6 +188,8 @@ 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
>
