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

Glauber Costa
2009-09-03T22:18:22Z

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

--
Glauber Costa.
"Free as in Freedom"
http://glommer.net

"The less confident you are, the more serious you have to act."