Description:
Boot up a RHEL 6.1 geust with a vf and with a memory close to or more than free memory in host, it will caused an oom and qemu process will be killed with oom. This will happen even the memory of guest is close to the free memory in host. Boot up the same guest with the same cmd line just remove the "-device pci-assign,host=03:10.0,id=test,iommu=1" option will not cause oom.

Version-Release number of selected component (if applicable):
kernel: 
2.6.32-211.el6.x86_64
kvm&qemu: 
qemu-img-0.12.1.2-2.200.el6.x86_64
gpxe-roms-qemu-0.9.7-6.9.el6.noarch
qemu-kvm-debuginfo-0.12.1.2-2.200.el6.x86_64
qemu-kvm-0.12.1.2-2.200.el6.x86_64
qemu-kvm-tools-0.12.1.2-2.200.el6.x86_64


How reproducible:
Always

Steps to Reproduce:
1. Reload the kvm and igb module with options support for device assign and SRIOV
$ modprobe -r kvm_intel;modprobe -r kvm; modprrobe -r igb
$ modprobe kvm allow_unsafe_assigned_interrupts=1
$ modprobe kvm_intel
$ modprobe igb max_vfs=7
2. Unbind device from host kernel driver. 
$ lspci |grep 82576
$ lspci -n -s 03:10.0
$ echo "8086 10ca" > /sys/bus/pci/drivers/pci-stub/new_id
$ echo 0000:03:10.0 > /sys/bus/pci/devices/0000\:03\:10.0/driver/unbind 
$ echo 0000:03:10.0 > /sys/bus/pci/drivers/pci-stub/bind 
3. Boot up guest with vf and memory close to free memory in host
$qemu -device pci-assign,host=03:10.0,id=test,iommu=1 -mem $free_memory or
$qemu -pcidevice host=03:10.0 -mem $free_memory

Actual results:
Host get oom and it kill qemu process sometimes make host kernel panic
Expected results:
Can boot up a guest normally

Additional info:
1. cmdline:
qemu-kvm -name 'vm1' -chardev socket,id=qmp_monitor_id_qmpmonitor1,path=/tmp/monitor-qmpmonitor1-20111024-135253-EMnq,server,nowait -mon chardev=qmp_monitor_id_qmpmonitor1,mode=control -chardev socket,id=serial_id_20111024-135253-EMnq,path=/tmp/serial-20111024-135253-EMnq,server,nowait -device isa-serial,chardev=serial_id_20111024-135253-EMnq -drive file='/root/autotest-devel/client/tests/kvm/images/RHEL-Server-6.1-32-virtio.qcow2',index=0,if=none,id=drive-virtio-disk1,media=disk,cache=none,format=qcow2,aio=native -device virtio-blk-pci,bus=pci.0,addr=0x4,drive=drive-virtio-disk1,id=virtio-disk1 -net none -m 11957 -smp 2,cores=1,threads=1,sockets=2 -cpu cpu64-rhel6,+sse2,+x2apic -spice port=8000,disable-ticketing -vga qxl   -rtc base=utc,clock=host,driftfix=slew -boot order=cdn,once=c,menu=off    -no-kvm-pit-reinjection  -M rhel6.2.0 -usb -device usb-tablet -enable-kvm -device pci-assign,host=03:10.0,id=test,iommu=1