Fwd: Re: kvm-31 seg fault

Fwd: Re: kvm-31 seg fault

[Chris Clayton]

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.

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

Chris

-------------------------------------------------------

-------------------------------------------------------------------------
This SF.net email is sponsored by: Splunk Inc.
Still grepping through log files to find problems?  Stop.
Now Search log events and configuration files using AJAX and a browser.
Download your FREE copy of Splunk now >>  http://get.splunk.com/

Re: Fwd: Re: kvm-31 seg fault

[Avi Kivity]

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.


-------------------------------------------------------------------------
This SF.net email is sponsored by: Splunk Inc.
Still grepping through log files to find problems?  Stop.
Now Search log events and configuration files using AJAX and a browser.
Download your FREE copy of Splunk now >>  http://get.splunk.com/

Re: Fwd: Re: kvm-31 seg fault

[Chris Clayton]

On Wednesday 25 July 2007, Avi Kivity wrote:
> 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?
>

Thanks Avi, that was it. The distro is (was) Peanut LInux, a Slackware 
derivative. But I've been adding, replacing and upgrading software for three 
or four years now, so it looks very little like the original. Anyway, it was 
glibc. Although it was a version (2.3.6) capable of supporting thread local 
storage (TLS), it wasn't compiled to actually do so. I've taken the 
opportunity to perform another upgrade and am now running glibc 2.5 with TLS 
support and kvm versions 31 and 33 each run fine.

Thanks for your help.

> > 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.

-- 
Beer is proof that God loves us and wants us to be happy - Benjamin Franklin

-------------------------------------------------------------------------
This SF.net email is sponsored by: Splunk Inc.
Still grepping through log files to find problems?  Stop.
Now Search log events and configuration files using AJAX and a browser.
Download your FREE copy of Splunk now >>  http://get.splunk.com/

Re: Fwd: Re: kvm-31 seg fault

[Gregory Haskins]

On Tue, 2007-07-24 at 22:02 +0000, Chris Clayton wrote:

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

If you can, run your failing setup under valgrind.  Its great for
finding stuff like that.

Regards,
-Greg



-------------------------------------------------------------------------
This SF.net email is sponsored by: Splunk Inc.
Still grepping through log files to find problems?  Stop.
Now Search log events and configuration files using AJAX and a browser.
Download your FREE copy of Splunk now >>  http://get.splunk.com/