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

This is a must before get virtqueue indexes (base) for live migration,
since the device could modify them after userland gets them. There are
individual ways to perform that action for some devices
(VHOST_NET_SET_BACKEND, VHOST_VSOCK_SET_RUNNING, ...) but there was no
way to perform it for any vhost device (and, in particular, vhost-vdpa).

Comments are welcome.

Eugenio Pérez (4):
  vdpa: Add stop operation
  vhost-vdpa: introduce STOP backend feature bit
  vhost-vdpa: uAPI to stop the device
  vdpa_sim: Implement stop vdpa op

 drivers/vdpa/vdpa_sim/vdpa_sim.c     | 21 +++++++++++++++++++
 drivers/vdpa/vdpa_sim/vdpa_sim.h     |  1 +
 drivers/vdpa/vdpa_sim/vdpa_sim_net.c |  3 +++
 drivers/vhost/vdpa.c                 | 31 ++++++++++++++++++++++++++++
 include/linux/vdpa.h                 |  6 ++++++
 include/uapi/linux/vhost.h           |  3 +++
 include/uapi/linux/vhost_types.h     |  2 ++
 7 files changed, 67 insertions(+)

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2.27.0