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



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




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