[Qemu-devel] [Bug 722311] Re: Segmentation fault if started without -enable-kvm parameter

[Bug Reporter]

It is a bit weird that www.qemu.org tells me to report my bugs on
launchpad, but replies to my bug report then appear ONLY on the
developer mailing list. How shall a lowly end-user know that he must
look there, too?

Anyway. On the developer mailing list, Markus Armbruster (Mon, 21 Feb
2011 09:00:25 +0100) requested:

> Stack backtrace, please!

When recompiling qemu 0.14.0 with "--enable-debug" for that purpose I
also played a bit with the CFLAGS. It turns out that qemu segfaults when
compiled with "-Os" in the CFLAGS, but not when compiled without
"-O<whatever>" in the CFLAGS. The GCC version is 4.5.2.

I have now probably lost the audience. But nevermind, here is the stack
backtrace from qemu compiled with "-Os":

root [~/sandbox] gdb qemu
GNU gdb (GDB) 7.2
Copyright (C) 2010 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 "i686-pc-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/bin/qemu...done.
(gdb) r
Starting program: /usr/bin/qemu 
[Thread debugging using libthread_db enabled]

Program received signal SIGSEGV, Segmentation fault.
raise_interrupt (intno=13, is_int=0, error_code=8, next_eip_addend=0)
    at /root/sandbox/stage4/qemu-0.14.0/target-i386/op_helper.c:1340
1340        env->exception_index = intno;
(gdb) bt
#0  raise_interrupt (intno=13, is_int=0, error_code=8, next_eip_addend=0)
    at /root/sandbox/stage4/qemu-0.14.0/target-i386/op_helper.c:1340
#1  0x08146e13 in raise_exception_err (exception_index=13, error_code=8)
    at /root/sandbox/stage4/qemu-0.14.0/target-i386/op_helper.c:1351
#2  0xda9abe00 in ?? ()
#3  0x00000000 in ?? ()
(gdb) 


and for comparison, the stack backtrace after compiling qemu with no CFLAGS at 
all:

root [~/sandbox] gdb qemu
GNU gdb (GDB) 7.2
Copyright (C) 2010 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 "i686-pc-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/bin/qemu...done.
(gdb) r
Starting program: /usr/bin/qemu 
[Thread debugging using libthread_db enabled]

Program exited normally.
(gdb) bt
No stack.
(gdb)

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https://bugs.launchpad.net/bugs/722311

Title:
  Segmentation fault if started without -enable-kvm parameter

Status in QEMU:
  New

Bug description:
  I start qemu (Linux) from the same USB memory stick on several
  computers. Up to and including qemu 0.12.5, I could use or not use
  qemu's "-enable-kvm" command line parameter as appropriate for the
  hardware, and qemu would run. In contrast, qemu 0.13.0 and 0.14.0
  segfault if started without "-enable-kvm". I get a black window
  appearing for fractions of a second, disappearing immediately, and
  then the error message "Segmentation fault".

  Hardware: Pentium 4, and Core 2 Duo.
  Command line: either "qemu" or "qemu -enable-kvm" (after manually loading the 
kvm-intel module on the Core 2 Duo).
  Reproducible: always.