Re: [Qemu-devel] segmentation fault in qemu-kvm-0.14.0

[Michael Tokarev <mjt@tls.msk.ru>]

09.03.2011 10:26, Stefan Weil wrote:
> Am 08.03.2011 23:53, schrieb Peter Lieven:
>> Hi,
>>
>> during testing of qemu-kvm-0.14.0 i can reproduce the following
>> segfault. i have seen similar crash already in 0.13.0, but had no time
>> to debug.
>> my guess is that this segfault is related to the threaded vnc server
>> which was introduced in qemu 0.13.0. the bug is only triggerable if a vnc
>> client is attached. it might also be connected to a resolution change
>> in the guest. i have a backtrace attached. the debugger is still
>> running if someone
>> needs more output
>>
[]
> Hi Peter,
> 
> did you apply this patch which fixes one of the known vnc problems
> (but is still missing in qemu git master):
> 
> http://lists.nongnu.org/archive/html/qemu-devel/2011-03/msg00256.html

This patch is not suitable for 0.14 since in current qemu/master quite
alot of stuff were changed in this area (bitmaps added), there's no
similar infrastructure in 0.14.

> Then you can read this thread:
> 
> http://lists.nongnu.org/archive/html/qemu-devel/2011-03/msg00313.html
> 
> And finally the following modifications of ui/vnc.c might help to see
> whether you experience the same kind of crash as I get here in
> my environment. They add assertions for bad memory access
> which occurs sometimes when a vnc client-server connection exists and
> the screen is refreshed after a resolution change.
> The code line with the //~ comment also includes a fix which
> works for me.

The same is true for this patch, but of a less extent: it can be applied
manually (the bitmap_empty context line).

I wonder if something similar actually exists in 0.13/0.14 too and needs
to be backported to -stable.

> Regards,
> Stefan W.

Thanks!

/mjt