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

[Julien Grall <julien@xxxxxxx>]

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.

Cheers,

--
Julien Grall