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

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

vhost: bugfix

This fixes a regression in vhost.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
# gpg: Signature made Mon 16 Apr 2018 17:12:59 BST
# gpg:                using RSA key 281F0DB8D28D5469
# 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:
  vhost: do not verify ring mappings when IOMMU is enabled

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