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

[Jason Gunthorpe <jgg@nvidia.com>]

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?

Jason