Re: [PATCH 0/2] iommufd: Only enforce_cache_coherency when allocating hwpt

[Baolu Lu]

On 10/23/23 10:55 AM, Tian, Kevin wrote:
> > From: Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx>
> > Sent: Saturday, October 21, 2023 9:33 AM
> >
> > On 2023/10/21 8:37, Nicolin Chen wrote:
> > > https://lore.kernel.org/linux-
> > iommu/20231020135501.GG3952@xxxxxxxxxx/
> > > The conversation above concluded that a hwpt should only enforce cache
> > > coherency per device at the stage of its allocation, and it should not
> > > be changed or updated in the attach/replace routines.
> > >
> > > Add two patches dropping the enforce_cache_coherency calls from attach
> > > and replce routines respectively, since they were introduced with two
> > > different commits.
> > >
> > > Nicolin Chen (2):
> > >     iommufd/device: Drop enforce_cache_coherency in
> > >       iommufd_device_do_replace
> > >     iommufd/device: Drop enforce_cache_coherency in
> > >       iommufd_hw_pagetable_attach
> > >
> > >    drivers/iommu/iommufd/device.c          | 19 ++-----------------
> > >    drivers/iommu/iommufd/hw_pagetable.c    |  2 +-
> > >    drivers/iommu/iommufd/iommufd_private.h |  1 -
> > >    3 files changed, 3 insertions(+), 19 deletions(-)
> >
> > Hi Kevin and Jason,
> >
> > With these two fixes, there's no issue in the intel driver any more. Do
> > I understand it right?
>
> But code-wise it's still good to explicitly disallow enforce-cc on a
> non-empty domain if there is no plan to support it. Just no Fix to
> stable.

Yes. Make sense. The device driver implementation should be self-
contained.

Best regards,
baolu