Re: [PATCH] vfio: mlx5, pds: add IOMMU_SUPPORT dependency

Jason Gunthorpe
2023-10-23T13:25:21Z

On Mon, Oct 23, 2023 at 02:55:13PM +0200, Arnd Bergmann wrote:
> On Mon, Oct 23, 2023, at 14:37, Joao Martins wrote:
> > On 23/10/2023 13:04, Jason Gunthorpe wrote:
> >> On Mon, Oct 23, 2023 at 01:55:03PM +0200, Arnd Bergmann wrote:
> >
> > Right -- IOMMU drivers need really IOMMUFD (as its usage is driven by IOMMUFD),
> > whereby vfio pci drivers don't quite need the iommufd support, only the helper
> > code support, as the vfio UAPI drives VF own dirty tracking.
> >
> >> I think it means IOMMUFD_DRIVER should be lifted out of the
> >> IOMMU_SUPPORT block somehow. I guess just move it into the top of
> >> drivers/iommu/Kconfig?
> >
> > iommufd Kconfig is only included in the IOMMU_SUPPORT kconfig if clause; so
> > moving it out from the iommufd kconfig out into iommu kconfig should fix it.
> > Didn't realize that one can select IOMMU_API yet have IOMMU_SUPPORT unset/unmet.
> > I'll make the move in v6
>
> Are there any useful configurations with IOMMU_API but
> not IOMMU_SUPPORT though? My first approach was actually

IOMMU_SUPPORT is just the menu option in kconfig, it doesn't actually
do anything functional as far as I can tell

But you can have IOMMU_API turned on without IOMMU_SUPPORT still on
power

I think the right thing is to combine IOMMU_SUPPORT and IOMMU_API into
the same thing.

Since VFIO already must depend on IOMMU_API it would be sufficient for
this problem too.

Jason