Re: qemu-kvm-1.1.0 crashing with kernel 3.5.0-rc6

[Chris Clayton <chris2553@googlemail.com>]

On 07/19/12 13:17, Avi Kivity wrote:
> On 07/19/2012 03:14 PM, Chris Clayton wrote:
>
>>> Change of diagnostics, unfortunately. qemu-kvm-1.0.1 can, in fact, crash
>>> on 3.5.0-rc6 (and rc7). I didn't get it earlier because it takes many
>>> times more invocations before the crash occurs with 1.0.1 and I haven't
>>> used qemu-kvm much in the past few weeks.
>>>
>>> I'm now checking whether I can get crashes (with 1.0.1 and/or 1.1.0) on
>>> linux-3.4.4. I'll report back in a day or two.
>>
>> I've started up qemu-kvm on kernel 3.4.4 many times and not see a crash.
>> That would indicate that the problem is in the kernel. However, I pulled
>> the latest and greatest from Linus yesterday evening and I now can't get
>> the crash there either, so whatever it was seems to have been fixed. If
>> I checkout and build 3.5.0-rc[1..7], I can get the crash pretty quickly,
>> so it's been fixed in the last few days.
>
> There were no kvm changes post-rc7.
>
Yes, I'm aware of that, Avi. This thread started because I was getting a 
crash in qemu-kvm, which I thought was only in v1.1.0. Later it turned 
out the the problem was also present in v1.0.1, but much harder to hit. 
However, it only ever happened with 3.5.0 kernels. 3.4.4, with either 
version of qemu-kvm, was stable. So then it seemed that the problem was 
in the kernel, (but not necessarily in the kvm code).

Something that's changed since rc7 has either fixed the problem or made 
it much harder to hit. With rc7 and earlier I can recreate the crash 
quite easily with qemu-kvm-1.1.0 and with enough runs of 1.0.1. With 
rc7+, I haven't been able to get a crash at all.

I'm not inclined to bisect to find out which patch provided the fix, but 
this mail should at least close the mail thread down tidily.

Chris