Re: [Xen-devel] DomU: kernel BUG at arch/x86/xen/enlighten.c:425

[James Sinclair <james.sinclair@xxxxxxxxxx>]

On 13/03/2013, at 9:56 AM, James Sinclair <james.sinclair@xxxxxxxxxx> wrote:

> On 12/03/2013, at 6:45 PM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
> 
>>>>> On 12.03.13 at 04:56, James Sinclair <james.sinclair@xxxxxxxxxx> wrote:
>> 
>> (re-adding xen-devel to Cc)
>> 
>>> I've done further testing and I have confirmed that I can trigger the bug 
>>> pretty reliably on several Xen versions:
>>> 
>>>   * xen-3.4.4
>>>   * xen-4.1.4
>>>   * xen-4.1.5-pre
>>> 
>>> Dom0 kernels range between 2.6.18 & 3.7.7-1. I've also tried quite a few 
>>> DomU 
>>> kernels and I can trigger it in everything I've tried between 2.6.39.1 and 
>>> 3.7.10. In the end, I haven't managed to find a combination of Xen, Dom0 & 
>>> DomU where I cannot trigger it.
>> 
>> Partly because you apparently never tried non-pvops DomU kernels.
>> But that's not the point here.
>> 
>>> As for the hypervisor log, I'm not seeing anything get logged at all. I 
>>> suspect that I'm not capturing them correctly. Using Xen 4.1.4 I added the 
>>> following to the command line:
>>> 
>>>   loglvl=all guest_loglvl=all sync_console console_to_ring earlyprintk=xen 
>>> debug loglevel=8
>> 
>> Now, this mixture of hypervisor and kernel options already
>> suggests that you don't look in the right place. Please put Xen
>> options on the Xen command line, and kernel ones on the kernel
>> line.
> 
> The documentation I found that mentioned using "earlyprintk=xen debug 
> loglevel=8" did not make it clear those are kernel options. I've corrected 
> that now:
> 
>    Hypervisor options: loglvl=all guest_loglvl=all sync_console 
> console_to_ring
>    Kernel options: earlyprintk=xen debug loglevel=8
> 
>> 
>>> I'm seeing extra logs from Xen during boot, but nothing when the bug is 
>>> triggered in the DomU. I'm assuming any extra logging will show up on the 
>>> console or in /var/log/xen/xend.log - is there somewhere else I should be 
>>> looking? Or something I'm not setting correctly?
>> 
>> They show up on the serial console (if in use) or in the output of
>> "xl dmesg" (or "xm dmesg" if xend is in use). Without extra
>> precautions, they _won't_ show up anywhere under /var/log.
> 
> I'm not seeing anything extra logged on the serial console nor in "xl dmesg" 
> when the bug hits. The only log entry I'm getting is a warning from 
> XendDomainInfo that the domain has crashed, and that's only logged when the 
> bug hits a critical process (usually init) that causes the domU kernel to 
> panic.
> 
> I'm working on building a hypervisor with "debug=y" enabled to see if that 
> gives me anything extra.

I've managed to set up a debug build of the 4.1.4 hypervisor and, with logging 
turned all the way up (as far as I can tell), nothing gets logged when the domU 
hits the kernel bug.

I'm not sure what to try next.

James
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