Description of problem:
boot a guest with the image located on NFS storage and virtio-scsi-pci, run iozone tool in the guest, and then disconnect the NFS server to generate a EIO, after that reconnect NFS, and resume the paused guest by running "cont" in QEMU monitor, but the QEMU core dump, fail to resume.

Version-Release number of selected component (if applicable):
host info:
# uname -r && rpm -q qemu-kvm-rhev
2.6.32-274.el6.x86_64
qemu-kvm-rhev-0.12.1.2-2.295.el6.x86_64
guest info:
guest name: RHEL-6.3-Snapshot-5-20120523.1-x86_64
application: iozone

How reproducible:
100%

Steps to Reproduce:
1.configure the NFS and mount it.
# cat /etc/exports 
/home *(rw,no_root_squash,sync)
...
# mount -o soft,timeo=15,retrans=3,nosharecache $ip_nfs_server:/home/ /mnt/
2.boot a guest with the image located on NFS storage and virtio-scsi-pci.
eg: <qemu-kvm-commands>-drive file=/mnt/RHEL-6.3-Snapshot-5-20120523.1-x86_64.qcow2,if=none,id=scsi_drive,format=qcow2,aio=native,cache=none,werror=stop,rerror=stop -device virtio-scsi-pci,id=scsi0 -device scsi-hd,drive=scsi_drive,scsi-id=1,lun=0,id=blk_image,bootindex=1
3.run iozone in the guest. <-----NOTE: It's very important
eg: # iozone -a
4.disconnect the NFS server to generate a EIO and check status.
# service nfs stop

(qemu) block I/O error in device 'scsi_drive': Input/output error (5)
block I/O error in device 'scsi_drive': Input/output error (5)
block I/O error in device 'scsi_drive': Input/output error (5)
block I/O error in device 'scsi_drive': Input/output error (5)
...
(qemu) info status
VM status: paused (io-error)
5.reconnect NFS server.
# service nfs restart
6.resume the paused guest by running "cont" in monitor.
(qemu) cont
  
Actual results:
after the step 6, the QEMU core dump.
(qemu) cont
(qemu) qemu-kvm: /builddir/build/BUILD/qemu-kvm-0.12.1.2/hw/scsi-disk.c:369: scsi_write_data: Assertion `r->req.aiocb == ((void *)0)' failed.

Program received signal SIGABRT, Aborted.
0x00007ffff57768a5 in raise () from /lib64/libc.so.6

(gdb) bt
#0  0x00007ffff57768a5 in raise () from /lib64/libc.so.6
#1  0x00007ffff5778085 in abort () from /lib64/libc.so.6
#2  0x00007ffff576fa1e in __assert_fail_base () from /lib64/libc.so.6
#3  0x00007ffff576fae0 in __assert_fail () from /lib64/libc.so.6
#4  0x00007ffff7e5ec51 in scsi_write_data (req=0x7fff4767d170) at /usr/src/debug/qemu-kvm-0.12.1.2/hw/scsi-disk.c:369
#5  0x00007ffff7e5e246 in scsi_dma_restart_bh (opaque=<value optimized out>) at /usr/src/debug/qemu-kvm-0.12.1.2/hw/scsi-bus.c:53
#6  0x00007ffff7e1ccd1 in qemu_bh_poll () at async.c:70
#7  0x00007ffff7dea6c9 in main_loop_wait (timeout=1000) at /usr/src/debug/qemu-kvm-0.12.1.2/vl.c:4032
#8  0x00007ffff7e0bdfa in kvm_main_loop () at /usr/src/debug/qemu-kvm-0.12.1.2/qemu-kvm.c:2244
#9  0x00007ffff7ded09c in main_loop (argc=20, argv=<value optimized out>, envp=<value optimized out>)
    at /usr/src/debug/qemu-kvm-0.12.1.2/vl.c:4202
#10 main (argc=20, argv=<value optimized out>, envp=<value optimized out>) at /usr/src/debug/qemu-kvm-0.12.1.2/vl.c:6427
(gdb)

Expected results:
VM resumed successfully without any error, and the guest can work correctlly.

Additional info:
my host cpuinfo:
# lscpu 
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                8
On-line CPU(s) list:   0-7
Thread(s) per core:    2
Core(s) per socket:    4
CPU socket(s):         1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 42
Stepping:              7
CPU MHz:               1600.000
BogoMIPS:              6782.72
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              8192K
NUMA node0 CPU(s):     0-7