Re: [PATCH v5 1/9] xen/arm: smccc: add support for SMCCCv1.2 extended input/output registers

[Jens Wiklander <jens.wiklander@xxxxxxxxxx>]

Hi,

On Thu, Aug 18, 2022 at 7:31 PM Julien Grall <julien@xxxxxxx> wrote:
>
> Hi Bertrand,
>
> On 18/08/2022 16:55, Bertrand Marquis wrote:
> >> On 18 Aug 2022, at 15:31, Julien Grall <julien@xxxxxxx> wrote:
> >>>> +/*
> >>>> + * void arm_smccc_1_2_smc(const struct arm_smccc_1_2_regs *args,
> >>>> + *                        struct arm_smccc_1_2_regs *res)
> >>>> + */
> >>>> +ENTRY(arm_smccc_1_2_smc)
> >>>> +    /* Save `res` and free a GPR that won't be clobbered */
> >>> The comment here should be fixed, you are clobbering x19 hence you need 
> >>> to save it.
> >>
> >> The comment is correct. x19 is one of the few registers that will not be 
> >> clobbered by the SMC call. But we still need a register below to store 
> >> 'args', so we need to free it (what you call clobber).
> >
> > Adding “by SMC call" would make this more clear
>
> I would be fine with that.

I'll update the comment.

Thanks,
Jens

>
> Cheers,
>
> --
> Julien Grall