[libvirt] [PATCH] qemu: Fix shutdown regression

[Daniel P. Berrange]

On Tue, Sep 20, 2011 at 02:06:49PM -0400, Dave Allan wrote:
> On Tue, Sep 20, 2011 at 07:39:15PM +0200, Jiri Denemark wrote:
> > The commit that prevents disk corruption on domain shutdown
> > (96fc4784177ecb70357518fa863442455e45ad0e) causes regression with QEMU
> > 0.14.* and 0.15.* because of a regression bug in QEMU that was fixed
> > only recently in QEMU git. With affected QEMU binaries, domains cannot
> > be shutdown properly and stay in a paused state. This patch tries to
> > avoid this by sending SIGKILL to 0.1[45].* QEMU processes. Though we
> > wait a bit more between sending SIGTERM and SIGKILL to reduce the
> > possibility of virtual disk corruption.
> 
> IMO, SIGKILL should only be sent at the explicit direction of the
> user, saying in effect, I'm ok with possible data corruption, I want
> the VM killed unconditionally.  I would rather leave VMs paused than
> risk corrupting data.  Let's get as much input as we can from the qemu
> folks before we go down this path.

If we want that, then we need to have a different way to deal with
this shutdown problem. Leaving VMs in a paused state is not
acceptable behaviour - our IRC channel has already been flooded
with people complaining about this and we've only released this
2 days ago.

This patch of Jiri's attempts to minimise the liklihood of hitting
a problem. If people want an absolute guarantee then they have the
option to update to a version of QEMU that has the fix, or distros
can backport the fix to QEMU and disable this bit in libvirt.

Daniel
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