Merge remote-tracking branch 'remotes/sstabellini/tags/xen-20170627-tag' into staging

Xen 2017/06/27

# gpg: Signature made Tue 27 Jun 2017 23:02:43 BST
# gpg:                using RSA key 0x894F8F4870E1AE90
# gpg: Good signature from "Stefano Stabellini <stefano.stabellini@eu.citrix.com>"
# gpg:                 aka "Stefano Stabellini <sstabellini@kernel.org>"
# Primary key fingerprint: D04E 33AB A51F 67BA 07D3  0AEA 894F 8F48 70E1 AE90

* remotes/sstabellini/tags/xen-20170627-tag:
  xen-disk: add support for multi-page shared rings
  xen-disk: only advertize feature-persistent if grant copy is not available
  xen/disk: don't leak stack data via response ring

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