Re: [Intel-gfx] [PATCH v2 4/7] vfio/mdev: Pass in a struct vfio_device * to vfio_dma_rw()

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Apr 22, 2022 at 01:50:00AM +0000, Tian, Kevin wrote:
> > From: Jason Gunthorpe <jgg@nvidia.com>
> > Sent: Friday, April 22, 2022 12:29 AM
> > 
> > Every caller has a readily available vfio_device pointer, use that instead
> > of passing in a generic struct device. The struct vfio_device already
> > contains the group we need so this avoids complexity, extra refcountings,
> > and a confusing lifecycle model.
> 
> Using the same description as last patch leaves the impression that
> the two patches do the exactly same type of change. But this
> patch actually includes one more change to grab a reference on the
> container. This is worth an explanation.

How about this:

Every caller has a readily available vfio_device pointer, use that instead
of passing in a generic struct device. Change vfio_dma_rw() to take in the
struct vfio_device and move the container users that would have been held
by vfio_group_get_external_user_from_dev() to vfio_dma_rw() directly, like
vfio_pin/unpin_pages().

Thanks,
Jason