Re: [RFC PATCH v3 14/15] Read and validate host SMMUv3 feature bits

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Jul 15, 2025 at 07:57:57PM -0700, Nicolin Chen wrote:
> > +    val = FIELD_EX32(s_accel->info.idr[5], IDR5, GRAN4K);
> > +    if (val < FIELD_EX32(s->idr[5], IDR5, GRAN4K)) {
> > +        s->idr[5] = FIELD_DP32(s->idr[5], IDR5, GRAN4K, val);
> > +    }
> > +    val = FIELD_EX32(s_accel->info.idr[5], IDR5, GRAN16K);
> > +    if (val < FIELD_EX32(s->idr[5], IDR5, GRAN16K)) {
> > +        s->idr[5] = FIELD_DP32(s->idr[5], IDR5, GRAN16K, val);
> > +    }
> > +    val = FIELD_EX32(s_accel->info.idr[5], IDR5, GRAN64K);
> > +    if (val < FIELD_EX32(s->idr[5], IDR5, GRAN64K)) {
> > +        s->idr[5] = FIELD_DP32(s->idr[5], IDR5, GRAN64K, val);
> 
> Unless there is some conflicts between the QEMU emulation and the
> SMMU HW, I think we should probably just override these fields to
> the HW values,

The qemu model should be fully independent of the underlying HW, it
should not override from HW.

It should check if the underlying supports the model and fail if it
doesn't.

Jason