Re: kvm-85rc5 Segmentation fault for m >= 2046 GB

[Donald Parsons <dparsons@brightdsl.net>]

On Mon, 2009-04-13 at 01:42 -0300, Marcelo Tosatti wrote:
> On Sun, Apr 12, 2009 at 06:14:12PM -0400, Donald Parsons wrote:
> > Required info:
> >  Intel Core 2 Duo E6600
> >  kvm version kvm-85rc5 seg faults (rc[13] fine; rc[24]?)
> >  Host kernel version: 2.6.29.1 SMP x86_64 (on Fedora 10)
> >  Guest: Fedora 11 beta x86_64 (host and guest updated)
> >  qemu cmd line:
> >   /usr/local/kvm/bin/qemu-system-x86_64 fc11Beta.img -m 2048 &
> >  Problem still present with either of -no-kvm-irqchip or
> >     -no-kvm-pit switch
> >  Problem also appears with the -no-kvm switch
> > 
> > In trying to make the core file smaller I found the
> > seg fault disappeared for anything less than 2048
> > and still appeared for other values above 2048.
> > (Interesting thing, m=2046 and 2047 got a little further, window
> > changed size before seg fault).  Everything up to 2045
> > worked.
> > Seg fault occurs quite early, last thing seen is:
> >   "Press F12 for boot menu"
> > followed by segfault about 3.5 to 4 seconds later.
> > 
> > Seems to be a problem with http://www.linux-kvm.org/page/Bugs
> > where it says about core files "Then get a backtrace of
> > the error with"  followed by nothing?
> 
> # gdb -c core.xxx qemu/x86_64-softmmu/qemu-system-x86_64
> 
> (gdb) bt 
> 
> Yes, the page is missing information, will be fixed.
> 
> > 
> > dmesg shows:
> > 
> > (these for m>=2048)
> > qemu-system-x86[9392] general protection ip:43c8e9 sp:7fffdfd955d0
> > error:0 in qemu-system-x86_64[400000+1f2000]
> > qemu-system-x86[9394] general protection ip:43c8e9 sp:7fffee13e970
> > error:0 in qemu-system-x86_64[400000+1f2000]
> > qemu-system-x86[9462] general protection ip:43c8e9 sp:7fff21ce3510
> > error:0 in qemu-system-x86_64[400000+1f2000]
> > qemu-system-x86[9522] general protection ip:43c8e9 sp:7fff7b4d4d10
> > error:0 in qemu-system-x86_64[400000+1f2000]
> > qemu-system-x86[9525] general protection ip:43c8e9 sp:7fff11aba2f0
> > error:0 in qemu-system-x86_64[400000+1f2000]
> > 
> > (next one  m=2046)
> > qemu-system-x86[9540] general protection ip:43c8f4 sp:7fffd6020850
> > error:0 in qemu-system-x86_64[400000+1f2000]
> > (next one  m=2047)
> > qemu-system-x86[9314] general protection ip:43c8f4 sp:7fffdcfe1810
> > error:0 in qemu-system-x86_64[400000+1f2000]

Okay, here is the backtrace:

Core was generated by `/usr/local/kvm/bin/qemu-system-x86_64
fc11Beta.img -m 2048 -no-quit'.
Program terminated with signal 11, Segmentation fault.
#0  0x000000000043c8e9 in fprintf ()
(gdb) bt
#0  0x000000000043c8e9 in fprintf ()
#1  0x00000000004951fa in fprintf ()
#2  0x000000000040861e in fprintf ()
#3  0x00000000004096ca in fprintf ()
#4  0x000000000052302a in fprintf ()
#5  0x000000000040df05 in fprintf ()
#6  0x0000003fa421e576 in __libc_start_main () from /lib64/libc.so.6
#7  0x0000000000406c69 in fprintf ()
#8  0x00007fff8e91ee58 in ?? ()
#9  0x000000000000001c in ?? ()
#10 0x0000000000000005 in ?? ()
#11 0x00007fff8e91f81d in ?? ()
#12 0x00007fff8e91f843 in ?? ()
#13 0x00007fff8e91f850 in ?? ()
#14 0x00007fff8e91f853 in ?? ()
#15 0x00007fff8e91f858 in ?? ()
#16 0x0000000000000000 in ?? ()

and dmesg shows for this same segfault:
loaded kvm module (kvm-85rc5)
qemu-system-x86[4551] general protection ip:43c8e9 sp:7fff8e91e100
error:0 in qemu-system-x86_64[400000+1f2000]

Don