Re: [Qemu-devel] Qemu 2.0 regression with xen: qemu crash on any domUs S.O. start

[Fabio Fantoni <fabio.fantoni@m2r.biz>]

Il 01/04/2014 18:24, Laszlo Ersek ha scritto:
> On 04/01/14 17:01, Fabio Fantoni wrote:
>> Today I tried latest qemu 2.0 compiled from git (commit
>> 63678e17cf399ff81b93417fe7bee8d6ef6b6b1b) on this dom0:
>> Debian 7 (Wheezy) 64 bit with kernel from package
>> linux-image-3.2.0-4-amd64 version 3.2.54-2 and all dependency packages
>> for xen, spice and usb redirection.
>> Seabios 1.7.3-3, spice 0.12.4-0nocelt2 and usbredir 0.6-2 compiled from
>> debian unstable sources.
>> The xen-unstable upstream commit is
>> 4787f667bcee205c56a27da59b766a53e1e929eb, plus these patches not upstream:
>> tools: various things just to build test
>> tools: Improve make debball
>> libxl: Add qxl vga interface support for upstream qemu
>> libxl: add basic spice support for pv domUs
>>
>> Qemu crashes always on domU S.O. start, on both pv and hvm domUs.
>>
>> Same dom0 with qemu 1.6 from xen-unstable repository used for some tests
>> yesterday and was full working.
>> I also update seabios to 1.7.4-4 compiled from debian unstable sources
>> but the problem persists.
>>
>> I looked on dom0 logs, qemu logs and xl dmesg and I found only a qemu
>> segfault related on each domU in dom0 syslog, for example the latest:
>> [  844.273170] qemu-system-i38[3545]: segfault at 8 ip 00007fa905dcc4c1
>> sp 00007fff41220810 error 4 in qemu-system-i386[7fa905ad5000+598000]
>>
>> If you need more informations, tests and/or logs tell me and I'll post
>> them.
> Whoever looks into this would be greatly helped:
> - if you bisected the issue (between 1.6 and 2.0-rcX),

I tried time ago qemu 1.7 and qemu 2.0 on start of development without 
problem on domUs start but I'll retry.

> - if you posted qemu's backtrace at the sigsegv.

I tried to use gdb following this old post:
https://lists.gnu.org/archive/html/qemu-devel/2011-12/msg02575.html
but with same changes:

/usr/lib/xen/bin# vi qemu-system-i386
#!/bin/sh
exec gdbserver 0.0.0.0:1234 /usr/lib/xen/bin/qemu-system-i386.bak "$@"

gdb /usr/lib/xen/bin/qemu-system-i386.bak
target remote localhost:1234

This command with gdb on qemu fails:
xl -vvv create /etc/xen/wheezy.cfg
...
libxl: error: libxl_dm.c:1378:device_model_spawn_outcome: domain 13 
device model: spawn failed (rc=-3)
libxl: error: libxl_create.c:1207:domcreate_devmodel_started: device 
model did not start: -3
libxl: debug: libxl_dm.c:1485:kill_device_model: Device Model signaled
...

the dom0 syslog show segfault also in this case and the qemu log is 
different on first lines (probably for gdbserver):
less /var/log/xen/qemu-dm-wheezy.log
Process /usr/lib/xen/bin/qemu-system-i386.bak created; pid = 8238
Listening on port 1234
Remote debugging from host 127.0.0.1
xc: error: linux_gnttab_set_max_grants: ioctl SET_MAX_GRANTS failed (22 
= Invalid argument): Internal error
xen be: qdisk-51712: xc_gnttab_set_max_grants failed: Invalid argument


gdb on xl create show:
(gdb) target remote localhost:1234
Remote debugging using localhost:1234
Reading symbols from /lib64/ld-linux-x86-64.so.2...(no debugging symbols 
found)...done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
0x00007ffff7dddaf0 in ?? () from /lib64/ld-linux-x86-64.so.2
(gdb)

(gdb) bt full
#0  0x00007ffff7dddaf0 in ?? () from /lib64/ld-linux-x86-64.so.2
No symbol table info available.
#1  0x0000000000000013 in ?? ()
No symbol table info available.
#2  0x00007fffffffe871 in ?? ()
No symbol table info available.
#3  0x00007fffffffe897 in ?? ()
No symbol table info available.
#4  0x00007fffffffe8a2 in ?? ()
No symbol table info available.
#5  0x00007fffffffe8a5 in ?? ()
No symbol table info available.
#6  0x00007fffffffe8ae in ?? ()
No symbol table info available.
#7  0x00007fffffffe8ef in ?? ()
No symbol table info available.
#8  0x00007fffffffe8f4 in ?? ()
No symbol table info available.
#9  0x00007fffffffe913 in ?? ()
No symbol table info available.
#10 0x00007fffffffe91f in ?? ()
No symbol table info available.
#11 0x00007fffffffe92b in ?? ()
No symbol table info available.
#12 0x00007fffffffe931 in ?? ()
---Type <return> to continue, or q <return> to quit---

the qemu include debug and is not stripped:
file /usr/lib/xen/bin/qemu-system-i386.bak
/usr/lib/xen/bin/qemu-system-i386.bak: ELF 64-bit LSB shared object, 
x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for 
GNU/Linux 2.6.26, 
BuildID[sha1]=0x5aa043b5524d74d166ead62527343080384d586b, not stripped
and I also tried:
aptitude install libc6-dbg
but same result.

I not understand what I missed for correct xl create and/or gdb 
informations.
Can someone help me please?

Thanks for any reply

>
> Laszlo
>
>