Re: [PATCH v1 1/4] iommu/arm-smmu-v3: Pass in vmid to arm_smmu_make_s2_domain_ste()

[Pranjal Shrivastava <praan@google.com>]

On Wed, Mar 05, 2025 at 09:44:30AM -0800, Nicolin Chen wrote:
> On Wed, Mar 05, 2025 at 08:50:17AM +0000, Shameerali Kolothum Thodi wrote:
> > > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> > > b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> > > index bd9d7c85576a..e08c4ede4b2d 100644
> > > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> > > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> > > @@ -887,7 +887,7 @@ struct arm_smmu_entry_writer_ops {
> > >  void arm_smmu_make_abort_ste(struct arm_smmu_ste *target);
> > >  void arm_smmu_make_s2_domain_ste(struct arm_smmu_ste *target,
> > >  				 struct arm_smmu_master *master,
> > > -				 struct arm_smmu_domain *smmu_domain,
> > > +				 struct arm_smmu_domain *smmu_domain,
> > > u16 vmid,
> > >  				 bool ats_enabled);
> > 
> > Now that vmid is an input, do we need some kind of validation here as
> > at least vmid = 0 is reserved I guess for bypass STEs.
> 
> Perhaps it should do a WARN_ON_ONCE(!vmid), as it doesn't make
> sense for a caller to make an S2-bypass STE with this function.
> 

+1, a warning should suffice as the caller isn't expected to call this
with vmid = 0. For the s2 bypass case, we already set vmid field to 0 in
make_cdtable_ste for clients who *really* want the vmid = 0.

> Thanks
> Nicolin
> 

Thanks
Praan