Re: HVM pvops failures (one more qemu-dm.strace obtained)

[Jeremy Fitzhardinge <jeremy@goop.org>]

Andrew Lyon wrote:
> On Tue, Feb 24, 2009 at 11:38 AM, Boris Derzhavets
> <bderzhavets@yahoo.com> wrote:
>   
>> I fixed error in hvm profile and got a similar qemu-dm.strace (
>> /usr/lib64/.../qemu-dm).
>>
>> --- On Mon, 2/23/09, Jeremy Fitzhardinge <jeremy@goop.org> wrote:
>>
>> From: Jeremy Fitzhardinge <jeremy@goop.org>
>> Subject: Re: [Xen-devel] HVM pvops failures
>> To: "Ian Jackson" <Ian.Jackson@eu.citrix.com>
>> Cc: "Andrew Lyon" <andrew.lyon@gmail.com>, "xen-devel@lists.xensource.com"
>> <xen-devel@lists.xensource.com>, "Ian Campbell" <Ian.Campbell@citrix.com>
>> Date: Monday, February 23, 2009, 7:12 PM
>>
>> Ian Jackson wrote:
>>     
>>> Andrew Lyon writes ("Re: [Xen-devel] HVM guest question (was Re:
>>>       
>> [PATCH] ioemu: Cleanup the code of PCI passthrough.)"):
>>     
>>>> On Mon, Feb 23, 2009 at 2:53 PM, Ian
>>>>         
>>  Jackson
>> <Ian.Jackson@eu.citrix.com> wrote:
>>     
>>>>> These messages are not very surprising.  Is it working ?
>>>>>
>>>>>           
>>>> No, when try to start HVM on Xen unstable with pv_ops kernel I get
>>>>         
>> this error:
>>     
>>> Ah.  This is rather odd.  Normally I would hope that xend would report
>>> an exit status.  (I haven't tried pvops with qemu.)
>>>
>>>
>>>       
>> Hm, I'm getting:
>> [2009-02-23 15:26:18 4380] WARNING (image:482) domain win7: device model
>> failure: pid 5409: died due to signal 7; see /var/log/xen/qemu-dm-win7.log
>>
>> Hm, signal 7 - SIGBUS.  I wonder if
>>
>> Using stub domains doesn't work either.
>>
>>     
>>> I would suggest running qemu-dm under strace.  This can be done easily
>>> enough with a simple wrapper script, something like:
>>>   #!/bin/sh
>>>   set -e
>>>   exec strace -vvs500 -f -o /root/qemu-dm.strace \
>>>
>>>       
>>  /usr/lib/xen/bin/qemu-dm "$@"
>>     
>>> and then give the name of the script as device_model in your config file.
>>>       
>
>
> Is there anything more I can do to help debug this problem? I am eager
> to do more testing with pv_ops and I have time to do it at the moment,
> but hvm support is currently broken so there is little I can do with
> my test box.
>   

I was hoping Ian J would pop up and say "Its broken like this!  Fix it 
like this!".

There does appear to be some incompatibility between the pvops dom0 and 
qemu which is causing this SIGBUS; it would be really useful to know 
what page qemu is trying to access.  It might be a problem in the pvops 
/proc/xen/privcmd implementation, or it could be a bug in qemu which 
happens to work with 2.6.18.

The alternative is to try stubdom, which should avoid the issue.  I 
haven't had much success in making it work, but it looks like I was not 
starting fs-backend.  I'll try again shortly.

    J