Re: [patch V2 31/33] iommu/vt-d: Enable PCI/IMS

Thomas Gleixner
2022-11-24T13:21:08Z

On Thu, Nov 24 2022 at 09:14, Jason Gunthorpe wrote:
> On Thu, Nov 24, 2022 at 10:37:53AM +0100, Thomas Gleixner wrote:
>> Jason said, that the envisioned Mellanox use case does not depend on the
>> IOMMU because the card itself has one which takes care of the
>> protections.
>
> Right, but that doesn't mean we need the physical iommu turned
> off. Setting the mlx pci device to identity mode is usually enough to
> get back to full performance.

Ok.

>> How are we going to resolve that dilemma?
>
> The outcome is we don't have a strategy right now to make IMS work in
> VMs. This series is all about making it work on physical machines,
> that has to be a good first step.
>
> I'm hoping the OCP work stream on SIOV will tackle how to fix the
> interrupt problems. Some of the ideas I've seen could be formed into
> something that would work in a VM.

Fair enough.

Let me put the limitation into effect then.

Thanks,

tglx