Re: [Xen-devel] Using debug-key 'o: Dump IOMMU p2m table, locks up machine

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Hello Jan,

Tuesday, September 4, 2012, 9:46:27 AM, you wrote:

>>>> On 04.09.12 at 09:08, Sander Eikelenboom <linux@xxxxxxxxxxxxxx> wrote:
>>> This one
>> 
>>>>(XEN) [2012-09-02 00:55:02] traps.c:3156: GPF (0060): ffff82c48015c9ee -> 
>> ffff82c480224b13
>> 
>>> also worries me. While Xen gracefully recovers from it, these
>>> messages still generally indicate a problem somewhere. Could
>>> you resolve the addresses to file:line tuples? And, assuming
>>> this happens in the context of doing something on behalf of
>>> the guest in the context of a guest vCPU, could you also
>>> check what guest side action triggers this (e.g. by adding a
>>> call to show_execution_state() alongside the printing of the
>>> message)?
>> 
>> Hope i have done it right:

> Yes.

>> Gives (complete dmesg attached:
>> 
>> (XEN) [2012-09-03 21:20:49] AMD-Vi: IO_PAGE_FAULT: domain = 14, device id = 
>> 0x0700, fault address = 0xa8ee82c0
>> (XEN) [2012-09-03 21:20:49] AMD-Vi: IO_PAGE_FAULT: domain = 14, device id = 
>> 0x0700, fault address = 0xa8ee8320
>> (XEN) [2012-09-04 03:00:34] traps.c:3156: GPF (0060): ffff82c48015c9ee -> 
>> ffff82c480224b73
>> (XEN) [2012-09-04 03:00:34] traps.c:3157:  show_execution_state(regs): 
>> (XEN) [2012-09-04 03:00:34] ----[ Xen-4.2.0-rc4-pre  x86_64  debug=y  Not 
>> tainted ]----
>> (XEN) [2012-09-04 03:00:34] CPU:    3
>> (XEN) [2012-09-04 03:00:34] RIP:    e008:[<ffff82c48015c9ee>] 
>> context_switch+0x394/0xeeb

> Now that - in the middle of context switch code - almost certainly
> wants to be fixed, but we first need to understand what it is (and
> how it gets triggered by the guest). I.e. once again this requires
> resolving to file/line - care to do the conversion yourself, or send
> (or make available somewhere) the very xen-syms?

> Jan

Hmm don't know how to get the file/line, only thing i have found is:

serveerstertje:/boot# gdb xen-syms-4.2.0-rc4-pre
GNU gdb (GDB) 7.0.1-debian
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /boot/xen-syms-4.2.0-rc4-pre...done.
(gdb) x/i 0xffff82c48015c9ee
0xffff82c48015c9ee <context_switch+916>:        mov    %edx,%gs
(gdb)


How to resolve the RIP could be a nice addition to the 
http://wiki.xen.org/wiki/Debugging_Xen, so one could easily refer to that on 
how to do it :-)

--
Sander


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