The -1 assumes that cvq device model is accounted in data_queue_pairs,
if cvq does not exists, but it's actually the opposite: Devices with
!cvq are ok but devices with cvq does not add the last queue to
data_queue_pairs.

This is not a problem to vhost-net, but it is to vhost-vdpa:
* Devices with cvq gets initialized at last data vq device model, not
at cvq one.
* Devices with !cvq never gets initialized, since last_index is the
first queue of the last device model.

Tested with vp_vdpa with host's vhost=on and vhost=off, and ctrol_vq
on and off.

v4:
* Rename last_index to index_end

v3:
* Recover cvq devices.
* Rename last_index to last_vq_index

v2:
* Delete all the conditional code instead of ROUND_DOWN in a
  deinitely too-bit-tricky way.

Eugenio Pérez (2):
  vhost: Rename last_index to vq_index_end
  vhost: Fix last vq queue index of devices with no cvq

 include/hw/virtio/vhost.h |  4 ++--
 hw/net/vhost_net.c        | 12 ++++++------
 hw/virtio/vhost-vdpa.c    |  2 +-
 3 files changed, 9 insertions(+), 9 deletions(-)

-- 
2.27.0