Description of problem:
fail to detect the hotpluging disk in guest under pci bridge on q35 machine type

Version-Release number of selected component (if applicable):
[root@jinzhao pci-bridge]# uname -r
3.10.0-509.el7.x86_64
[root@jinzhao pci-bridge]# rpm -qa |grep qemu-kvm-rhev
qemu-kvm-rhev-debuginfo-2.6.0-26.el7.x86_64
qemu-kvm-rhev-2.6.0-26.el7.x86_64


How reproducible:
3/3

Steps to Reproduce:
1.Boot guest with pci bridge on q35 machine type
/usr/libexec/qemu-kvm \
-M q35 \
-cpu SandyBridge \
-nodefaults -rtc base=utc \
-m 4G \
-smp 2,sockets=2,cores=1,threads=1 \
-enable-kvm \
-name rhel7.3 \
-uuid 990ea161-6b67-47b2-b803-19fb01d30d12 \
-smbios type=1,manufacturer='Red Hat',product='RHEV Hypervisor',version=el6,serial=koTUXQrb,uuid=feebc8fd-f8b0-4e75-abc3-e63fcdb67170 \
-k en-us \
-nodefaults \
-serial unix:/tmp/serial0,server,nowait \
-boot menu=on \
-bios /usr/share/seabios/bios.bin \
-chardev file,path=/home/pci-bridge/seabios.log,id=seabios \
-device isa-debugcon,chardev=seabios,iobase=0x402 \
-qmp tcp:0:6666,server,nowait \
-device i82801b11-bridge,bus=pcie.0,id=bridge0 \
-device pci-bridge,bus=bridge0,id=bridge1,chassis_nr=1 \
-drive file=/home/pci-bridge/big.img,if=none,id=drive-virtio-disk0,format=qcow2,cache=none,werror=stop,rerror=stop \
-device virtio-blk-pci,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 \
-device virtio-net-pci,netdev=tap10,mac=9a:6a:6b:6c:6d:6e,bus=bridge1,addr=0x2.0 -netdev tap,id=tap10 \
-drive file=/home/pci-bridge/block1.qcow2,if=none,id=drive-virtio-disk1,format=qcow2,cache=none,werror=stop,rerror=stop \
-device virtio-blk-pci,drive=drive-virtio-disk1,id=virtio-disk1,bus=bridge1,addr=0x1.0 \
-device VGA,id=video,bus=bridge1,addr=0x3.0 \
-vnc :2 \
-monitor stdio \

2. Hot plug disk on qmp
{"execute":"__com.redhat_drive_add", "arguments": {"file":"/home/pci-bridge/block2.qcow2","format":"qcow2","id":"test2"
}}
{"return": {}}
{"execute":"device_add","arguments":{"driver":"virtio-blk-pci","drive":"test2","id":"test2","bus":"bridge1","addr":"0x4.0"}}
{"return": {}}
{"execute":"__com.redhat_drive_add", "arguments": {"file":"/home/pci-bridge/test.raw","format":"raw","id":"drive_datadisk0"}}
{"return": {}}
{"execute":"device_add","arguments":{"driver":"virtio-scsi-pci","id":"scsi1","bus":"bridge1","addr":"0x5.0"}}
{"return": {}}
{"execute":"device_add","arguments":{"driver":"scsi-hd","drive":"drive_datadisk0","id":"device_datadisk0","bus":"scsi1.0"}}
{"return": {}}

3.check the block in hmp
(qemu) info block
drive-virtio-disk0 (#block138): /home/pci-bridge/big.img (qcow2)
    Cache mode:       writeback, direct

drive-virtio-disk1 (#block361): /home/pci-bridge/block1.qcow2 (qcow2)
    Cache mode:       writeback, direct

test2 (#block511): /home/pci-bridge/block2.qcow2 (qcow2)
    Cache mode:       writeback

drive_datadisk0 (#block747): /home/pci-bridge/test.raw (raw)
    Cache mode:       writeback

4. check the block in guest

Actual results:
Block devices didn't be found in guest
[root@localhost ~]# lsblk
NAME          MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda           252:0    0  30G  0 disk 
├─vda1        252:1    0   1G  0 part /boot
└─vda2        252:2    0  29G  0 part 
  ├─rhel-root 253:0    0  26G  0 lvm  /
  └─rhel-swap 253:1    0   3G  0 lvm  [SWAP]
vdb           252:16   0   5G  0 disk 
└─vdb1        252:17   0   5G  0 part 

Expected results:
Guest can be found in guest

Additional info: