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SubjectRe: [PATCH v3 3/5] vfio/iommu_type1: Remove the domain->ops comparison
On Fri, Jun 24, 2022 at 03:28:33PM -0300, Jason Gunthorpe wrote:
> On Thu, Jun 23, 2022 at 01:00:27PM -0700, Nicolin Chen wrote:
> > The domain->ops validation was added, as a precaution, for mixed-driver
> > systems.
> >
> > Per Robin's remarks,
> > * While bus_set_iommu() still exists, the core code prevents multiple
> > drivers from registering, so we can't really run into a situation of
> > having a mixed-driver system:
> > https://lore.kernel.org/kvm/6e1280c5-4b22-ebb3-3912-6c72bc169982@arm.com/
> >
> > * And there's plenty more significant problems than this to fix; in future
> > when many can be permitted, we will rely on the IOMMU core code to check
> > the domain->ops:
> > https://lore.kernel.org/kvm/6575de6d-94ba-c427-5b1e-967750ddff23@arm.com/
> >
> > So remove the check in VFIO for simplicity.
>
> As discussed we can't remove this check, multiple iommus on different
> busses are allowed today and VFIO does not restrict its attempts to
> attach a pre-existing domain to a single group or bus.
>
> Please go back to the original version with the ops check in the core
> code.

Robin convinced me, so never mind :)

Jason

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