Writes to the Device Status field race with DEVICE_NEEDS_RESET

[Olivier Delande <olivier.delande@gmail.com>]

As far as I understand the Virtio 1.1 spec, a driver must not clear
any bit in the Device Status field when it writes a non-zero value.
How can it comply with this requirement, when the device may be
concurrently setting DEVICE_NEEDS_RESET? There does not seem to be any
facility to atomically set some bits and leave the others unchanged.