> From: Liu, Yi L <yi.l.liu@xxxxxxxxx> > Sent: Monday, December 19, 2022 4:47 PM > > Allow the vfio_device file to be in a state where the device FD is > opened but the device is not opened. This inbetween state is not used 'but the device cannot be used by userspace (i.e. its .open_device() hasn't been called)" > when the device FD is spawned from the group FD, however when we create > the device FD directly by opening a cdev it will be opened in the > blocked state. > > In the blocked state, currently only the bind operation is allowed, > other device accesses are not allowed. Completing bind will allow user > to further access the device. > > This is implemented by adding a flag in struct vfio_device_file to mark > the blocked state and using a simple smp_load_acquire() to obtain the > flag value and serialize all the device setup with the thread accessing > this device. > > Due to this scheme it is not possible to unbind the FD, once it bound it > remains bound until the FD is closed. Could you elaborate why it's impossible to unbind the fd with this scheme? > > + /* Paired with smp_store_release() in vfio_device_open/close() */ > + access = smp_load_acquire(&df->access_granted); > + if (!access) > + return -EINVAL; > + -EPERM?
