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

virtio, pc: fixes

Some fixes to fallback from using virtio caching,
pls a minor vm gen id fix.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
# gpg: Signature made Wed 15 Mar 2017 17:59:25 GMT
# 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:
  virtio-pci: reset modern vq meta data
  Revert "virtio: unbreak virtio-pci with IOMMU after caching ring translations"
  pci: introduce a bus master container
  virtio: validate address space cache during init
  virtio: destroy region cache during reset
  virtio: guard against NULL pfn
  Bugfix: Handle error if VM Generation ID device not present

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