Re: [PATCH v1 4/4] iommu/arm-smmu-v3-iommufd: Allow a shared s2_parent to allocate vSMMU

[Jason Gunthorpe]

On Wed, Mar 05, 2025 at 09:01:40AM +0000, Shameerali Kolothum Thodi wrote:

> >  	if (!(smmu->features & ARM_SMMU_FEAT_NESTING))
> >  		return ERR_PTR(-EOPNOTSUPP);
> > 
> > -	if (s2_parent->smmu != master->smmu)
> > -		return ERR_PTR(-EINVAL);
> > -
> 
> Not sure we can just relax this like this. What if the two physical SMMUs are different in
> functionality/features? Do we need some kind of sanity check here?

Yes, a function to check if a domain's iopgtbl config is compatible
with the instance is required.

Jason