[Intel-gfx] [PATCH v4 09/19] vfio/pci: Accept device fd for hot reset

[Liu, Yi L]

> From: Tian, Kevin <kevin.tian at intel.com>
> Sent: Friday, February 24, 2023 10:48 AM
> 
> > From: Jason Gunthorpe
> > Sent: Friday, February 24, 2023 10:36 AM
> >
> > On Fri, Feb 24, 2023 at 02:21:33AM +0000, Tian, Kevin wrote:
> >
> > > Yi, while you are incorporating this change please also update the
> > > uapi header. Rename 'group_fds[]' to 'fds[]' and add comment to
> > > explain that it could be an array of group fds or a single iommufd.
> >
> > Upon reflection we can probably make it even simpler and just have a 0
> > length fd array mean to use the iommufd the vfio_device is already
> > associated with
> >
> > And the check for correctness can be simplified to simply see if each
> > vfio_device in the dev_set is attached to the same iommufd ctx
> > pointer instead of searching the xarray.

How about the hot reset info path? We can still keep reporting the
current information to userspace. Isn't it?

another tricky question. If user passess iommufd down for reset
in the vfio iommufd compatible mode, should we support it as
well?

> yes, this is simpler
> 
> >
> > Would need to double check that the locking is OK but seems doable
> >
> 
> Locking is fine since dev_set->lock is already held in the reset path.

dev_set->lock is held prior to call bind_iommufd, so I agree locking
is ok.

Regards,
Yi Liu