Re: [PATCH v7 13/14] iommu/arm-smmu-v3: Report events that belong to devices attached to vIOMMU

Pranjal Shrivastava
2025-02-25T16:50:52Z

On Mon, Feb 24, 2025 at 07:35:05PM -0400, Jason Gunthorpe wrote:
> On Mon, Feb 24, 2025 at 01:56:46PM -0800, Nicolin Chen wrote:
>
> > > Just thinking out loud here:
> > > I understand the goal here is to "emulate" an IOMMU. But I'm just
> > > wondering if we could report struct events instead of the raw event?
> > >
> > > For example, can't we have something like arm_smmu_event here with the
> > > sid changed to vsid?
> > >
> > > Are we taking the raw event since we want to keep the `u64 event_data[]`
> > > field within `struct iommufd_vevent` generic to all architectures?
> >
> > The ABIs for vSMMU are defined in the HW languange, e.g. cmd, ste.
> > Thus, here evt in raw too.
>
> Right, the point is that it gives as a safe uABI that is effectively
> being managed by ARM.
>
> If we make our own thing then we have to take the responsiblity to
> make it safe and extensible. I don't see a justification to do that..
>
> It is the same discussion we had around the vSTE as input, the raw
> invalidation command and the IDRs. Since we've already done 'follow
> the SMMU spec' so many times already now we should keep doing it.

Ack. Undertsood. Thanks for the explanation :)

-Praan