Re: [PATCH] qemu-kvm: fix segfault when running kvm without /dev/kvm, falling back to non-accelerated mode

Dustin Kirkland
2009-09-04T16:06:46Z

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On Fri, 2009-09-04 at 08:22 +0100, Mark McLoughlin wrote:
> On Thu, 2009-09-03 at 19:18 -0300, Glauber Costa wrote:
> > On Thu, Sep 3, 2009 at 6:48 PM, Dustin Kirkland<kirkland@canonical.com> wrote:
> > > On Thu, Sep 3, 2009 at 3:01 PM, Mark McLoughlin<markmc@redhat.com> wrote:
> > >> On Thu, 2009-09-03 at 12:31 -0500, Dustin Kirkland wrote:
> > >>> qemu-kvm: fix segfault when running kvm without /dev/kvm, falling back
> > >>> to non-accelerated mode
> > >>>
> > >>> We're seeing segfaults on systems without access to /dev/kvm. It
> > >>> looks like the global kvm_allowed is being set just a little too late
> > >>> in vl.c. This patch moves the kvm initialization a bit higher in the
> > >>> vl.c main, just after options processing, and solves the segfaults.
> > >>> We're carrying this patch in Ubuntu 9.10 Alpha. Please apply
> > >>> upstream, or advise if and why this might not be the optimal solution.
> > >>
> > >> Ah discussion about an alternative fix for this fizzled out recently:
> > >>
> > >> http://www.mail-archive.com/kvm@vger.kernel.org/msg19890.html
> > >
> > > Ah, thanks Mark. In that thread, I found Daniel's suggestion the most
> > > reasonable, and user-friendly:
> > >
> > > On Mon, Jul 27, 2009 at 1:44 PM, Daniel P. Berrange<berrange@redhat.com> wrote:
> > >> Well, we could go for logic like:
> > >>
> > >> * No arg given => try kvm, try kqemu, try tcg
> > >> * --accelmode arg given => try $arg, and fail if unavailable
> > >>
> > >> then libvirt would simply always supply --accelmode for all VMs,
> > >> while people running qemu manually would get best available
> > I sent some patches to do that, but they were incomplete, and I was
> > preempted by something else.
> > If you want, you can wait for my cycles to come back, or pick from where I left

Thanks for the pointer, Glauber. My cycles a bit constrained too, but
I'll have a look when I get a chance.

> In the meantime, can we commit to stable-0.11 either Dustin's fix or
> this:
>
> http://git.et.redhat.com/?p=qemu-fedora.git;a=commitdiff;h=aa1620047b

+1. We're looking for something agreeable in stable-0.11, that solves
the segfault and proceeds without VT acceleration.

--
:-Dustin

Dustin Kirkland
Canonical, LTD
kirkland@canonical.com
GPG: 1024D/83A61194

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