Re: Fwd: Re: kvm-31 seg fault

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Chris Clayton wrote:
> Forgot to cc this to the list, sorry
> ----------  Forwarded Message  ----------
>
> Subject: Re: [kvm-devel] kvm-31 seg fault
> Date: Tuesday 24 July 2007
> From: Chris Clayton <chris2553-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>
> To: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
>
> Hi again Avi,
>
> On Sunday 22 July 2007, you wrote:
>   
>> Chris Clayton wrote:
>>     
>>> On Sunday 22 July 2007, you wrote:
>>>       
>>>> Chris Clayton wrote:
>>>>         
>>>>> Hi,
>>>>>
>>>>> I'm getting a seg fault running kvm-31 on linux-2.6.22.1-cfs-v19 and
>>>>> linux-2.6.22-git17.
>>>>>
>>>>> If I use the kvm-31 kernel modules with qemu from kvm-29, all is OK
>>>>> Also, running "non-kvm" guests, such as Windows ME, works fine with
>>>>> kvm-31.
>>>>>
>>>>> I have an strace log but its over 99 Kilobytes, so I haven't attached
>>>>> it to this mail. More than happy to compress it and send it by private
>>>>> mail, if required.
>>>>>
>>>>> I'm not subscribed, so please cc me.
>>>>>           
>>>> Please send it to me.  What guest are you running?  Is the host 32-bit
>>>> or 64-bit?
>>>>         
>>> Attached is the log from 2.6.22-git17
>>>
>>> The host is 32bit and the guest is freebsd-6.2 although I get the same
>>> seg fault with slackware 10.2 and damn small linux 3.1 (all 32 bit).
>>>       
>> Unfortunately that doesn't help.  Can you generate a core ('ulimit -c
>> unlimited' may help) and get a stacktrace from gdb?
>>     
>
> I've been doing some more digging around here and thought I'd report my 
> findings. I've found that under kvm 31 and 33, qemu-system-x86_64 always 
> fails with a seg fault when the (__thread) variable vcpu_env (declared at 
> line 33 of qemu-kvm.c) is accessed in kvm_update_interrupt_request(). I've 
> inserted useless statements (printf()s and assignments) at the head of the 
> function, and always get the seg fault at the first access to the variable.
>
> I'm building qemu with gcc-3.4.6, but to eliminate a fault in that compiler, 
> I've also built the application on my laptop with gcc-3.3.6 and copied the 
> binary over to my desktop machine. I still get the seg fault.
>   

What's the host distro and glibc version?  Perhaps they're too old to
support __thread?


> Sorry if this is just noise on your line, but I thought I'd send it just in 
> case it's useful.
>
>   

It isn't noise, this is helping us getting kvm better.



-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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