[Bug 1576093] Re: [SRU] block migration fail with libvirt since version 1.2.17

[Rafael David Tinoco]

For Ubuntu Xenial (Mitaka), Yakkety (Newton), Zesty: Commit 0d34fbabc1
fixes the issue for vhost-net kernel. Vhost-net kernel doesn't use
shared log so the verification is not used and apparmor profiles won't
block the live migration. With customers using vhost-user that might
still cause migration problems, but, likely, those are the vast
minority.

commit 0d34fbabc13891da41582b0823867dc5733fffef
Author: Rafael David Tinoco <rafael.tinoco at canonical.com>
Date:   Mon Oct 24 15:35:03 2016 +0000

    vhost: migration blocker only if shared log is used

    Commit 31190ed7 added a migration blocker in vhost_dev_init() to
    check if memfd would succeed. It is better if this blocker first
    checks if vhost backend requires shared log. This will avoid a
    situation where a blocker is added inappropriately (e.g. shared
    log allocation fails when vhost backend doesn't support it).

    Signed-off-by: Rafael David Tinoco <rafael.tinoco at canonical.com>
    Reviewed-by: Marc-André Lureau <marcandre.lureau at redhat.com>
    Reviewed-by: Michael S. Tsirkin <mst at redhat.com>
    Signed-off-by: Michael S. Tsirkin <mst at redhat.com>

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 131f164..25bf67f 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1122,7 +1122,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
         if (!(hdev->features & (0x1ULL << VHOST_F_LOG_ALL))) {
             error_setg(&hdev->migration_blocker,
                        "Migration disabled: vhost lacks VHOST_F_LOG_ALL feature.");
-        } else if (!qemu_memfd_check()) {
+        } else if (vhost_dev_log_is_shared(hdev) && !qemu_memfd_check()) {
             error_setg(&hdev->migration_blocker,
                        "Migration disabled: failed to allocate shared memory");
         }

The "final" fix for upstream fix is being finished by me, but, might not
be suitable for SRU since it will add features in qemu (and likely to
libvirt) in order for the vhost log file to be passed (by using an
already opened file descriptor). This will require changes in libvirt
and nova-compute but this change will, finally, allow security driver to
apply rules to vhost log file for shared logs (mostly for vhost-user
drivers).

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https://bugs.launchpad.net/bugs/1576093

Title:
  [SRU] block migration fail with libvirt since version  1.2.17

Status in Ubuntu Cloud Archive:
  Invalid
Status in Ubuntu Cloud Archive mitaka series:
  Fix Released
Status in OpenStack Compute (nova):
  Fix Released
Status in nova package in Ubuntu:
  Fix Released
Status in nova source package in Xenial:
  Fix Released
Status in nova source package in Yakkety:
  Fix Released

Bug description:
  [Impact]

  Try to do block migration but fail and libvirt reports that

  "Selecting disks to migrate is not implemented for tunneled migration"

  Nova:  a4e15e329f9adbcfe72fbcd6acb94f0743ad02f8

  libvirt: 1.3.1

  [Test Case]

  reproduce:

  default devstack setting and do block migration (no shared
  instance_dir and shared instance storage used)

  [Regression Potential]

  Patch was cherry picked from upstream gerrit review, which was cherry
  picked with little change from master branch.

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