Re: [PATCH v10 10/13] iommu/arm-smmu-v3: Check for SVA features

Will Deacon
2020-12-09T20:09:07Z

On Wed, Dec 09, 2020 at 07:49:09PM +0000, Krishna Reddy wrote:
> > > Why is BTM mandated for SVA? I couldn't find this requirement in
> > > SMMU spec (Sorry if I missed it or this got discussed earlier). But
> > > if performance is the
> > only concern here,
> > > is it better just to allow it with a warning rather than limiting
> > > SMMUs without
> > BTM?
> >
> > It's a performance concern and requires to support multiple
> > configurations, but the spec allows it. Are there SMMUs without BTM
> > that need it?
>
> The Tegra Next Generation SOC uses arm-smmu-v3, but it doesn't have support for BTM.
> Do you have plan to get your earlier patch to handle invalidate
> notifications into upstream sometime soon?

Is that a limitation of the SMMU implementation, the interconnect or the
integration?

Will