Description
The guest was crashed while detach the 82576 vf card from the guest which has been attached
the same vf twice.

Versions
kernel-3.10.0-18.el7.x86_64
libvirt-1.1.1-5.el7.x86_64
qemu-kvm-1.5.3-3.el7.x86_64

Steps
1.Prepare a runnig guest
# virsh list --all
 Id    Name                           State
----------------------------------------------------
 3     rhelnew3                       running

2.Prepare a vf's xml
# virsh nodedev-dumpxml pci_0000_0f_10_7
<device>
  <name>pci_0000_0f_10_7</name>
  <path>/sys/devices/pci0000:00/0000:00:1c.6/0000:0c:00.0/0000:0d:02.0/0000:0f:10.7</path>
  <parent>pci_0000_0d_02_0</parent>
  <driver>
    <name>igbvf</name>
  </driver>
  <capability type='pci'>
    <domain>0</domain>
    <bus>15</bus>
    <slot>16</slot>
    <function>7</function>
    <product id='0x10ca'>82576 Virtual Function</product>
    <vendor id='0x8086'>Intel Corporation</vendor>

# cat vf.xml
<hostdev mode='subsystem' type='pci' managed='yes'>
            <source>
              <address bus='15' slot='16' function='7'/>
            </source>
  </hostdev>

3.Attach the vf to the guest
# virsh attach-device rhelnew3 vf.xml
Device attached successfully

4.Attach it again
# virsh attach-device rhelnew3 vf.xml
error: Failed to attach device from vf.xml
error: Requested operation is not valid: PCI device 0000:0f:10.7 is in use by domain rhelnew3

5.Detach the vf from the guest, vf will be detached successfully, however, the guest was destroyed automatically
# virsh detach-device rhelnew3 vf.xml
Device detached successfully

Check the guest's status
# virsh list --all
 Id    Name                           State
----------------------------------------------------
 -     rhelnew3                       shut off



6.Check the log in libvirtd.log
2013-09-17 05:05:06.743+0000: 20588: error : qemuMonitorIORead:515 : Unable to read from monitor: Connection reset by peer

check the log in qemu's log
char device redirected to /dev/pts/4 (label charserial0)
qemu: hardware error: pci write failed, ret = -1 errno = 13

CPU #0:
RAX=0000000000000006 RBX=0000000000000000 RCX=00000000000010ae RDX=0000000000000cfc
RSI=0000000000000097 RDI=0000000080004004 RBP=ffff88003d4a3b48 RSP=ffff88003d4a3b20
R8 =0000000000000002 R9 =0000000000000006 R10=0000000000000040 R11=0000000000000001
R12=0000000000000002 R13=0000000000000000 R14=0000000000000006 R15=0000000000000040
RIP=ffffffff814d35a7 RFL=00000046 [---Z-P-] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0000 0000000000000000 ffffffff 00c00000
CS =0010 0000000000000000 ffffffff 00a09b00 DPL=0 CS64 [-RA]
SS =0018 0000000000000000 ffffffff 00c09300 DPL=0 DS   [-WA]
DS =0000 0000000000000000 ffffffff 00c00000
FS =0000 0000000000000000 ffffffff 00c00000
GS =0000 ffff88003fc00000 ffffffff 00c00000
LDT=0000 0000000000000000 ffffffff 00c00000
TR =0040 ffff88003fc11a00 00002087 00008b00 DPL=0 TSS64-busy
GDT=     ffff88003fc0a000 0000007f
IDT=     ffffffffff529000 00000fff
CR0=8005003b CR2=00007f0ccc648f84 CR3=000000003c29f000 CR4=000006f0
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
DR6=00000000ffff0ff0 DR7=0000000000000400
EFER=0000000000000d01
FCW=037f FSW=0000 [ST=0] FTW=00 MXCSR=00009fc0
FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
XMM00=6e69616d6f646c61636f6c2e74736f68 XMM01=ffffffffffffffffffffffffffffffff
XMM02=00000000000000000000000000000000 XMM03=00000000000000000000000000000000
XMM04=00000000000000000000000000000000 XMM05=40404040404040404040404040404040
XMM06=5b5b5b5b5b5b5b5b5b5b5b5b5b5b5b5b XMM07=20202020202020202020202020202020
XMM08=00000000000000200000002000000000 XMM09=ff000000000000ffff0000ffff000000
XMM10=00000000000000000000000000000000 XMM11=ffffffffffffffffffffffffffffffff
XMM12=00000000000000000000000000000000 XMM13=00000000000000000000000000000000
XMM14=00000000000000000000000000000000 XMM15=00000000000000000000000000000000
2013-09-17 05:05:06.744+0000: shutting down


Actual result
The guest was crashed  while detach the vf the from the guest

Expect result
The guest shouldn't be crashed while detach the vf from the guest