Re: [PATCH v2 14/18] iommu/arm-smmu-v3: Support domains with shared CDs

[Michael Shavit]

On Wed, Jun 14, 2023 at 5:57 PM Robin Murphy <robin.murphy@xxxxxxx> wrote:
>
> In practice it would be entirely reasonable to only support
> cross-instance attach between instances with matching capabilities such
> that they *can* share the pagetable directly.

On Wed, Jun 14, 2023 at 8:10 PM Jason Gunthorpe <jgg@xxxxxxxxxx> wrote:
> When we talk about multi instance support, it means the iommu_domain -
> in whatever fixed IO page table format it uses - can be attached to
> any SMMU instance that supports it as a compatible page table format.
>
> ARM doesn't quite reach this model, but once it passes the finalize
> step it does. The goal is to move finalize to allocate. So for your
> purposes you can ignore the difference.

Got you. Failing the atach when the page table format is incompatible
with the smmu device is a lot easier to handle. I didn't notice that
SVA was already checking this elsewhere.
I can give the multi-instance support a try (with the rest of these
patches on top) and send it out as a follow-up series to this one.

> I think it is good to make progress, it looked to me like the first
> part stood alone fairly well and was an improvement on its own.

Sorry for the noobie question; it's not 100% obvious to me what the
next step is here. Is there anything I should do to progress that
first part forward?