[Intel-gfx] [PATCH v4 16/19] vfio: Add VFIO_DEVICE_BIND_IOMMUFD

[Yan Zhao]

On Wed, Feb 22, 2023 at 08:59:51AM -0400, Jason Gunthorpe wrote:
> On Wed, Feb 22, 2023 at 07:44:12AM +0000, Liu, Yi L wrote:
> > > From: Tian, Kevin <kevin.tian at intel.com>
> > > Sent: Wednesday, February 22, 2023 3:40 PM
> > > 
> > > > From: Liu, Yi L <yi.l.liu at intel.com>
> > > > Sent: Tuesday, February 21, 2023 11:48 AM
> > > >
> > > > +
> > > > +void vfio_device_cdev_close(struct vfio_device_file *df)
> > > > +{
> > > > +	struct vfio_device *device = df->device;
> > > > +
> > > > +	mutex_lock(&device->dev_set->lock);
> > > > +	if (!smp_load_acquire(&df->access_granted)) {
> > > 
> > > there is no contention with another one changing this flag at this
> > > point so directly accessing it is fine.
> > 
> > make sense. 
> 
> Have to use READ_ONCE though
>
Just a curious question:
given df->access_granted is now written with device->dev_set->lock held and
also read with this lock held in vfio_device_cdev_close(), is READ_ONCE
still required? And what about df->iommufd ?

Thanks
Yan