Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

# gpg: Signature made Fri 30 Jun 2017 12:46:17 BST
# gpg:                using RSA key 0x9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <[email protected]>"
# gpg:                 aka "Stefan Hajnoczi <[email protected]>"
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  virtio-pci: use ioeventfd even when KVM is disabled
  tests: fix virtio-net-test ISR dependence
  tests: fix virtio-blk-test ISR dependence
  tests: fix virtio-scsi-test ISR dependence
  libqos: add virtio used ring support
  libqos: fix typo in virtio.h QVirtQueue->used comment
  virtio-blk: trace vdev so devices can be distinguished

Signed-off-by: Peter Maydell <[email protected]>