Re: segfault at start with latest qemu-kvm.git

[Jan Kiszka <jan.kiszka@web.de>]

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Jan Kiszka wrote:
> David S. Ahern wrote:
>> On 03/03/2010 04:20 PM, Jan Kiszka wrote:
>>> David S. Ahern wrote:
>>>>
>>>> On 03/03/2010 04:08 PM, Jan Kiszka wrote:
>>>>> David S. Ahern wrote:
>>>>>> With latest qemu-kvm.git I am getting a segfault at start:
>>>>>>
>>>>>> /tmp/qemu-kvm-test/bin/qemu-system-x86_64 -m 1024 -smp 2 \
>>>>>>   -drive file=/images/f12-x86_64.img,if=virtio,cache=none,boot=on
>>>>>>
>>>>>> kvm_create_vcpu: Invalid argument
>>>>>> Segmentation fault (core dumped)
>>>>>>
>>>>>>
>>>>>> git bisect points to:
>>>>>>
>>>>>> Bisecting: 0 revisions left to test after this (roughly 0 steps)
>>>>>> [52b03dd70261934688cb00768c4b1e404716a337] qemu-kvm: Move
>>>>>> kvm_set_boot_cpu_id
>>>>>>
>>>>>>
>>>>>> $ git show
>>>>>> commit 7811d4e8ec057d25db68f900be1f09a142faca49
>>>>>> Author: Marcelo Tosatti <mtosatti@redhat.com>
>>>>>> Date:   Mon Mar 1 21:36:31 2010 -0300
>>>>>>
>>>>>>
>>>>>> If I manually back out the patch it will boot fine.
>>>>>>
>>>>> Problem persists after removing the build directory and doing a fresh
>>>>> configure && make? I'm asking before taking the bug (which would be
>>>>> mine, likely) as I recently spent some hours "debugging" a volatile
>>>>> build system issue.
>>>>>
>>>>> Jan
>>>>>
>>>> Before sending the email I pulled a fresh clone in a completely
>>>> different directory (/tmp) to determine if it was something I
>>>> introduced. I then went back to my usual location, unapplied the patch
>>>> and it worked fine.
>>> OK, that reason can be excluded. What's your host kernel kvm version?
>>>
>>> (Of course, the issue does not show up here. But virtio currently does
>>> not boot for me - independent of my patch.)
>>>
>>> Jan
>>>
>> Fedora Core 12,
>>
>> Linux daahern-lx 2.6.31.12-174.2.22.fc12.x86_64 #1 SMP Fri Feb 19
>> 18:55:03 UTC 2010 x86_64 x86_64 x86_64 GNU/Linux
>>
> 
> Reproduced after switching back to kvm-kmod-2.6.31, will debug.
> 

Subtle memory corruption: qemu_malloc is returning a pointer that
happens to become kvm_state twice. I bet my patch just exchanges some of
the involved parties and exposes the issue more prominently. Trying to
understand malloc's issue now...

Jan


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