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

Jason Gunthorpe
2023-10-21T16:39:19Z

On Sat, Oct 21, 2023 at 09:32:32AM +0800, Baolu Lu wrote:
> 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?

I think so, as long as it is an allocation only time flag there isn't
much trouble for the driver.

VFIO, I think, still does the old algorithm however.

Jason