[Intel-gfx] [PATCH v1 1/5] iommufd: Create access in vfio_iommufd_emulated_bind()

[Jason Gunthorpe]

On Mon, Mar 20, 2023 at 11:11:51PM +0800, Yi Liu wrote:
> 
> 
> On 2023/3/20 22:49, Jason Gunthorpe wrote:
> > On Wed, Mar 15, 2023 at 02:03:09AM -0700, Nicolin Chen wrote:
> > > Hi,
> > > 
> > > On Wed, Mar 15, 2023 at 06:50:53AM +0000, Tian, Kevin wrote:
> > > 
> > > > > So, this preparatory series will add a pair of simple attach()
> > > > > and detach() APIs. Then the cdev series will add the locking
> > > > > and the ioas_unpin stuff as a rework of the detach() API.
> > > 
> > > > > I think they can be something mingled... the sample code that
> > > > > I sent previously could take care of those conditions. But, I
> > > > > am also thinking a bit that maybe attach() does not need the
> > > > > locking? I can do a separate replace() function in this case.
> > > > > 
> > > > 
> > > > w/o locking then you need smp_store_release() and its pair.
> > > > 
> > > > anyway it's not in perf critical path. Keeping lock for attach
> > > > is simpler and safe.
> > > 
> > > OK. Basically I followed what Jason suggested by having three
> > > APIs and combined Kevin's inputs about the difference between
> > > the attach/replace(). I also updated the replace changes, and
> > > rebased all nesting (infrastructure, VT-d and SMMU):
> > > https://github.com/nicolinc/iommufd/commits/wip/iommufd_nesting-03142023
> > > 
> > > The major three changes for those APIs:
> > > [1] This adds iommufd_access_attach() in this series:
> > >      "iommufd: Create access in vfio_iommufd_emulated_bind()"
> > >      https://github.com/nicolinc/iommufd/commit/34fba7509429380f828fb23dcca5ceaeb40e22b5
> > > [2] This adds iommufd_access_detach() in the cdev series:
> > >      "iommufd/device: Add iommufd_access_detach() API"
> > >      https://github.com/nicolinc/iommufd/commit/4110522146ca1fc0d5321c04a097e2c9d9e26af4
> > > [3] This adds iommufd_access_replace() in the replace series:
> > >      "iommufd: Add iommufd_access_replace() API"
> > >      https://github.com/nicolinc/iommufd/commit/36507fa9f0f42cf1a5bebe7c9bc2bf319b7654a8
> > > 
> > > Please check if they look okay, so that Yi can integrate them
> > > accordingly to the emulated/cdev series.
> > 
> > I don't understand why this is being put in front of the cdev series?
> 
> because we want to make emulated devices have iommufd_access in the
> bind, then it can return iommufd_access->obj.id to userspace when
> adding cdev.

Ah OK

Jason