[PATCH v4 0/2] vduse: Add suspend

["Eugenio Pérez" <eperezma@redhat.com>]

Implement suspend operation for vduse devices, so vhost-vdpa will offer
that backend feature and userspace can effectively suspend the device.

This is a must before get virtqueue indexes (base) for live migration,
since the device could modify them after userland gets them.

This patch does not implement resume, so VMM resets the whole device
to recover from a live migration failure.  Resume optimization can be
implemented on top of these patches, as other vDPA devices have done in
the past.

This series applies on top of e372c4ca7931cadb5cbee1cd9124cfad38fa2391,
replacing all the previous patches.

v4:
* Add preparatory patch to not flush the kick and irq works under rwsem
  (MST).
* Fix jump over a semaphore guard (Nathan Chancellor).
* Fix take the device semaphore in the vq spinlock context (MST).
* Add suspend guard at vq_signal_irqfd so the device will not send an
  IRQ after suspend.

v3:
* Expand the patch message with information about resume operation.

v2:
* Take the rwsem only before the actual kick, not in vduse_vdpa_kick_vq.
  This assures that we're not in a critical section.

Eugenio Pérez (2):
  vduse: do not take rwsem at reset work flush
  vduse: Add suspend

 drivers/vdpa/vdpa_user/vduse_dev.c | 164 +++++++++++++++++++++--------
 include/uapi/linux/vduse.h         |   4 +
 2 files changed, 127 insertions(+), 41 deletions(-)

-- 
2.54.0