Description of problem:
Have no idea. Came back to the machine and had the crash warning. It seems to have killed one of my kvm virtual machines temporarilly. Seems to have powered back on ok though.

Version-Release number of selected component:
qemu-system-x86-1.4.2-15.fc19

Additional info:
reporter:       libreport-2.1.12
backtrace_rating: 4
cmdline:        /usr/bin/qemu-system-x86_64 -machine accel=kvm -name DebWebServ -S -machine pc-1.2,accel=kvm,usb=off -cpu Opteron_G4,+nodeid_msr,+wdt,+skinit,+ibs,+osvw,+cr8legacy,+extapic,+cmp_legacy,+fxsr_opt,+mmxext,+osxsave,+fma,+monitor,+ht,+vme -m 4096 -smp 2,sockets=2,cores=1,threads=1 -uuid 7521faad-bf0f-04b8-88fd-41260faa4d04 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/DebWebServ.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 -drive if=none,id=drive-ide0-1-0,readonly=on,format=raw -device ide-cd,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -drive file=/var/lib/libvirt/images/WheezyWeb.img,if=none,id=drive-virtio-disk0,format=qcow2,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x6,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -netdev tap,fd=23,id=hostnet0,vhost=on,vhostfd=24 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:a6:b2:bc,bus=pci.0,addr=0x3 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -chardev spicevmc,id=charchannel0,name=vdagent -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=com.redhat.spice.0 -spice port=5900,tls-port=5901,addr=0.0.0.0,disable-ticketing,x509-dir=/etc/pki/libvirt-spice,seamless-migration=on -vga qxl -global qxl-vga.ram_size=67108864 -global qxl-vga.vram_size=67108864 -device intel-hda,id=sound0,bus=pci.0,addr=0x4 -device hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x7
crash_function: kvm_cpu_exec
executable:     /usr/bin/qemu-system-x86_64
kernel:         3.13.6-100.fc19.x86_64
runlevel:       N 5
type:           CCpp
uid:            0
var_log_messages: Apr  5 23:01:19 grim-desktop abrt-hook-ccpp[30062]: Saved core dump of pid 1529 (/usr/bin/qemu-system-x86_64) to /var/tmp/abrt/ccpp-2014-04-05-23:00:54-1529 (4710047744 bytes)

Truncated backtrace:
Thread no. 1 (2 frames)
 #2 kvm_cpu_exec at /usr/src/debug/qemu-1.4.2/kvm-all.c:1575
 #3 qemu_kvm_cpu_thread_fn at /usr/src/debug/qemu-1.4.2/cpus.c:759