Re: [PATCH v4 00/12] Initial support for SMMUv3 nested translation

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Nov 13, 2024 at 10:55:41AM +0800, Baolu Lu wrote:
> On 11/13/24 09:23, Jason Gunthorpe wrote:
> > > https://github.com/Linaro/linux-kernel-uadk/tree/6.12-wip
> > > https://github.com/Linaro/qemu/tree/6.12-wip
> > > 
> > > Still need this hack
> > > https://github.com/Linaro/linux-kernel-uadk/commit/
> > > eaa194d954112cad4da7852e29343e546baf8683
> > > 
> > > One is adding iommu_dev_enable/disable_feature IOMMU_DEV_FEAT_SVA,
> > > which you have patchset before.
> > Yes, I have a more complete version of that here someplace. Need some
> > help on vt-d but hope to get that done next cycle.
> 
> Can you please elaborate this a bit more? Are you talking about below
> change

I need your help to remove IOMMU_DEV_FEAT_IOPF from the intel
driver. I have a patch series that eliminates it from all the other
drivers, and I wrote a patch to remove FEAT_SVA from intel..

> +	ret = iommu_dev_enable_feature(idev->dev, IOMMU_DEV_FEAT_SVA);
> +	if (ret)
> +		return ret;
> 
> in iommufd_fault_iopf_enable()?
> 
> I have no idea about why SVA is affected when enabling iopf.

It is ARM not implementing the API correctly. Only SVA turns on the
page fault reporting mechanism.

In the new world the page fault reporting should be managed during
domain attachment. If the domain is fault capable then faults should
be delivered to that domain. That is the correct time to setup the
iopf mechanism as well.

So I fixed that and now ARM and AMD both have no-op implementations of
IOMMU_DEV_FEAT_IOPF and IOMMU_DEV_FEAT_SVA. Thus I'd like to remove it
entirely.

Jason