Re: [PATCH v1 2/8] firmware: arm_rmm: Add VSMMU commands and fields

[Nicolin Chen <nicolinc@nvidia.com>]

On Wed, Oct 28, 2026 at 09:35:09AM -0300, Jason Gunthorpe wrote:
> On Wed, Oct 28, 2026 at 09:49:53AM +0000, Shameer Kolothum Thodi wrote:
> > > +static inline unsigned long rsi_arch_dev_activate(phys_addr_t base,
> > > +						  unsigned long dev_type)
> > > +{
> > > +	struct arm_smccc_res res;
> > > +
> > > +	arm_smccc_1_1_invoke(SMC_RSI_ARCH_DEV_ACTIVATE, base,
> > > dev_type, &res);
> > 
> > These calls leave unused input registers unspecified, whereas
> > DEN0137 bet3 B1.2 marks them SBZ. Could we explicitly zero them?
> > 
> > "On calling an RMI or RSI command, any of X1- X16 which are not
> >  specified as input values in the command definition SBZ"
> 
> That seems too broad, Linux doesn't even support the x8-x16 inputs in
> the macros. I think the spec has errd here.
> 
> Requiring zeroing of x0-x7 is sort of reasonable. Any future use of
> x8-x16 (including outputs) should require a direct opt in of the OS to
> indicate it supports this bank of registers.
> 
> Otherwise you probably need a new macro helper for this protocol..

We could probably replace it with:
	arm_smccc_smc(SMC_RSI_ARCH_DEV_ACTIVATE, base, dev_type, 0, 0, 0, 0, 0,
		      &res);

This should specify those unused inputs.

Nicolin