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

Tian, Kevin
2023-10-23T02:55:53Z

> From: Baolu Lu <baolu.lu@linux.intel.com>
> 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@nvidia.com/
> > 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.