Re: [PATCH v1 15/16] iommu/arm-smmu-v3: Add viommu cache invalidation support

Nicolin Chen
2024-08-19T18:38:53Z

On Mon, Aug 19, 2024 at 03:28:11PM -0300, Jason Gunthorpe wrote:
> On Mon, Aug 19, 2024 at 11:19:39AM -0700, Nicolin Chen wrote:
>
> > > But nesting enablment with out viommu is alot less useful than I had
> > > thought :(
> >
> > Actually, without viommu, the hwpt cache invalidate alone could
> > still support non-SVA case?
>
> That is what I thought, but doesn't the guest still have to invalidate
> the CD table entry # 0?

I recall it doesn't. The CD cache invalidation is required in the
viommu invalidation for an SVA case where we need a PASID number
to specify CD to the substream. But the CD to the default stream
is only changed during a vSTE setup, and the host knows the PASID
number (=0)?

> > Though we still have the blocker at the msi mapping... It still
> > requires a solution, even for viommu series.
>
> Yes, small steps. The point of this step was to get the nested paging
> only (without msi, pri, etc, etc)

Ack.

Thanks
Nicolin