[Intel-gfx] [PATCH v9 16/25] iommufd/device: Add iommufd_access_detach() API

[Jason Gunthorpe]

On Tue, Apr 04, 2023 at 04:45:12PM -0600, Alex Williamson wrote:
> On Sat,  1 Apr 2023 08:18:24 -0700
> Yi Liu <yi.l.liu at intel.com> wrote:
> 
> > From: Nicolin Chen <nicolinc at nvidia.com>
> > 
> > Previously, the detach routine is only done by the destroy(). And it was
> > called by vfio_iommufd_emulated_unbind() when the device runs close(), so
> > all the mappings in iopt were cleaned in that setup, when the call trace
> > reaches this detach() routine.
> > 
> > Now, there's a need of a detach uAPI, meaning that it does not only need
> > a new iommufd_access_detach() API, but also requires access->ops->unmap()
> > call as a cleanup. So add one.
> > 
> > However, leaving that unprotected can introduce some potential of a race
> > condition during the pin_/unpin_pages() call, where access->ioas->iopt is
> > getting referenced. So, add an ioas_lock to protect the context of iopt
> > referencings.
> > 
> > Also, to allow the iommufd_access_unpin_pages() callback to happen via
> > this unmap() call, add an ioas_unpin pointer, so the unpin routine won't
> > be affected by the "access->ioas = NULL" trick.
> > 
> > Reviewed-by: Kevin Tian <kevin.tian at intel.com>
> > Tested-by: Terrence Xu <terrence.xu at intel.com>
> > Tested-by: Yanting Jiang <yanting.jiang at intel.com>
> > Signed-off-by: Nicolin Chen <nicolinc at nvidia.com>
> > Signed-off-by: Yi Liu <yi.l.liu at intel.com>
> > ---
> >  drivers/iommu/iommufd/device.c          | 76 +++++++++++++++++++++++--
> >  drivers/iommu/iommufd/iommufd_private.h |  2 +
> >  include/linux/iommufd.h                 |  1 +
> >  3 files changed, 74 insertions(+), 5 deletions(-)
> 
> Does this need to go in via iommufd first?  There seems to be quite a
> bit of churn in iommufd/device.c vs the vfio_mdev_ops branch (ie. it
> doesn't apply). Thanks,

I think it is best to stay with this series, Yi has to rebase it

Jason