unmapping of persistent grants in qemu

I have just uploaded a modified version of qemu to my testing PPA[1]. I assumed your primary environment is Trusty. As soon as that is build you can get the updated qemu by adding that PPA. If you need packages for a different release, let me know.

[1] https://launchpad.net/~smb/+archive/ubuntu/xen?field.series_filter=trusty

This bug was fixed in the package qemu - 2.1+dfsg-7ubuntu2

---------------
qemu (2.1+dfsg-7ubuntu2) vivid; urgency=low

  * d/p/upstream-xen_disk-fix-unmapping-of-persistent-grants.patch:
    Cherry-pick of qemu-upstream patch to fix issues with persistent
    grants and the PV backend (Qdisk) (LP: #1394327).
 -- Stefan Bader <email address hidden> Fri, 28 Nov 2014 13:14:37 +0100

SRU justification:

Impact: As soon as dom0 starts qemu it will try to locally attach QCOW(2) images in case a PV guest is using those. This results in the described errors and sometimes the whole host is rendered unusable.

Fix: Cherry picking an upstream patch (which was done already for Vivid) resolves the issues.

Testcase: Prepare a PV guest that uses a QCOW2 image and try to start it. Depends on Xen starting dom0 (bug #1396068).

Hello Xing, or anyone else affected,

Accepted qemu into trusty-proposed. The package will build now and be available at http://launchpad.net/ubuntu/+source/qemu/2.0.0+dfsg-2ubuntu1.10 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

Hello Xing, or anyone else affected,

Accepted qemu into utopic-proposed. The package will build now and be available at http://launchpad.net/ubuntu/+source/qemu/2.1+dfsg-4ubuntu6.4 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

Hi,

I am pretty busy this week. I shall be able to do the test this weekend or
next week. Thanks,

-Xing

On Tue, Dec 16, 2014 at 7:18 AM, Chris J Arges <email address hidden>
wrote:

> Hello Xing, or anyone else affected,
>
> Accepted qemu into utopic-proposed. The package will build now and be
> available at http://launchpad.net/ubuntu/+source/qemu/2.1+dfsg-
> 4ubuntu6.4 in a few hours, and then in the -proposed repository.
>
> Please help us by testing this new package. See
> https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to
> enable and use -proposed. Your feedback will aid us getting this update
> out to other Ubuntu users.
>
> If this package fixes the bug for you, please add a comment to this bug,
> mentioning the version of the package you tested, and change the tag
> from verification-needed to verification-done. If it does not fix the
> bug for you, please add a comment stating that, and change the tag to
> verification-failed. In either case, details of your testing will help
> us make a better decision.
>
> Further information regarding the verification process can be found at
> https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in
> advance!
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1394327
>
> Title:
> unmapping of persistent grants in qemu
>
> Status in qemu package in Ubuntu:
> Fix Released
> Status in qemu source package in Trusty:
> Fix Committed
> Status in qemu source package in Utopic:
> Fix Committed
> Status in Debian GNU/Linux:
> Fix Released
>
> Bug description:
> A patch was discussed in xen-devel mailing list, to deal with unmapping
> of persistent grants in qemu for Xen on 12 Nov 2014. This patch is not
> included in any stable qemu release (including 2.0.2, 2.1.2 and 2.2.0-rc2 )
> yet. The patch is available here.
>
> http://lists.xenproject.org/archives/html/xen-devel/2014-11/msg01112.html
>
> Without this patch, when creating a xen guest from OpenStack, using
> the Xen+libvirt approach, it will result in dom0 kernel crashes, with
> dmesg as following.
>
>
> [ 9443.130600] blkfront: xvda: flush diskcache: enabled; persistent
> grants: enabled; indirect descriptors: disabled;
> [ 9443.132818] xvda: xvda1
> [ 9444.604489] xen:grant_table: WARNING: g.e. 0x30 still in use!
> [ 9444.604496] deferring g.e. 0x30 (pfn 0xffffffffffffffff)
> [ 9444.604499] xen:grant_table: WARNING: g.e. 0x31 still in use!
> [ 9444.604502] deferring g.e. 0x31 (pfn 0xffffffffffffffff)
> [ 9444.604505] xen:grant_table: WARNING: g.e. 0x32 still in use!
> [ 9444.604508] deferring g.e. 0x32 (pfn 0xffffffffffffffff)
> ==== lots of them====
> [ 9444.604719] xen:grant_table: WARNING: g.e. 0xe still in use!
> [ 9444.604721] deferring g.e. 0xe (pfn 0xffffffffffffffff)
> [ 9444.604723] xen:grant_table: WARNING: g.e. 0xd still in use!
> [ 9444.604725] deferring g.e. 0xd (pfn 0xffffffffffffffff)
> [ 9448.325408] ------------[ cut here ]------------
> [ 9448.325421] WARNING: CPU: 5 PID: 19902 at
> /build/buildd/linux-3.13.0/arch/x86/xen/multicalls.c:129 xen_mc_flush+0x
> ...

Upgraded a Trusty and Utopic host with qemu from proposed (after also upgrading xen for bug #1396068). After that defined a PV guest using a qcow2 image and booted that. No errors in dmesg and both VMs started.

thanks for verifying it, Stefan!

This bug was fixed in the package qemu - 2.0.0+dfsg-2ubuntu1.10

---------------
qemu (2.0.0+dfsg-2ubuntu1.10) trusty; urgency=low

  * Apply an upstream qemu patch to fix issues with persistent grants
    on qcow images accessed by dom0 (LP: #1394327).
 -- Stefan Bader <email address hidden> Mon, 15 Dec 2014 09:56:34 +0100

The verification of the Stable Release Update for qemu has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

This bug was fixed in the package qemu - 2.1+dfsg-4ubuntu6.4

---------------
qemu (2.1+dfsg-4ubuntu6.4) utopic; urgency=low

  * Apply an upstream qemu patch to fix issues with persistent grants
    on qcow images accessed by dom0 (LP: #1394327).
 -- Stefan Bader <email address hidden> Mon, 15 Dec 2014 09:49:17 +0100