Merge remote-tracking branch 'remotes/mst/tags/for_upstream' into staging

Merge remote-tracking branch 'remotes/mst/tags/for_upstream' into staging

virtio, vhost: fixes, features

IOTLB support in vhost-user.
A bunch of fixes all over the place.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
# gpg: Signature made Fri 02 Jun 2017 17:33:25 BST
# gpg:                using RSA key 0x281F0DB8D28D5469
# gpg: Good signature from "Michael S. Tsirkin <mst@kernel.org>"
# gpg:                 aka "Michael S. Tsirkin <mst@redhat.com>"
# Primary key fingerprint: 0270 606B 6F3C DF3D 0B17  0970 C350 3912 AFBE 8E67
#      Subkey fingerprint: 5D09 FD08 71C8 F85B 94CA  8A0D 281F 0DB8 D28D 5469

* remotes/mst/tags/for_upstream:
  spec/vhost-user spec: Add IOMMU support
  vhost-user: add slave-req-fd support
  vhost-user: add vhost_user to hold the chr
  vhost: rework IOTLB messaging
  vhost: propagate errors in vhost_device_iotlb_miss()
  virtio-serial: fix segfault on disconnect
  virtio: add virtqueue_alloc_element tracepoint
  virtio-serial-bus: Unset hotplug handler when unrealize

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>