[Qemu-devel] how to dynamically add a block device using qmp?

[Ken Chiang]

Hello,

I am trying to add a block device dynamically using qmp and are having some 
issues.

After successfully adding the block device using "blockdev-add" and verifying 
that it has been added using "query-block", I am unable to see the block device 
in the VM under /dev/sdXX

I am using ubuntu14.04LTS: qmp version: 
{"QMP": {"version": {"qemu": {"micro": 0, "minor": 0, "major": 2}, "package": " 
(Debian 2.0.0+dfsg-2ubuntu1.2)"}, "capabilities": []}}

Here's what I am doing:
1.  /usr/bin/kvm-spice -hda kvmimages/ubuntu.image -m 768 -usbdevice tablet 
-vnc :5 -qmp tcp:localhost:,server,nowait

2.  telnet localhost 

3.  In the telnet session run:
{"execute":"qmp_capabilities"}
{"return": {}}
{ "execute": "blockdev-add",
   "arguments": { "options" : {
"id": "disk1",
"driver": "qcow2",
"file": { "driver": "file",
"filename": "testvm.qc2" } } } }
{"return": {}}

{ "execute": "query-block" }

4. query-block returns the device "disk1", but when I check the vm:
   # vncviewer :5
   
there are no new devices.

I thought that maybe it is a hotplug SATA bug detailed here: 
http://ubuntuforums.org/showthread.php?t=1998055

but running:
#rescan-scsi-bus resulted in no new block devices.

Thanks for any help!

Ken

Re: [Qemu-devel] [EXTERNAL] Re: how to dynamically add a block device using qmp?

[Ken Chiang]

I also tried to add a virt io device to the frontend but still no disc in the 
VM.  Am I missing anything else?


{"QMP": {"version": {"qemu": {"micro": 0, "minor": 0, "major": 2}, "package": " 
(Debian 2.0.0+dfsg-2ubuntu1.2)"}, "capabilities": []}}
{"execute":"qmp_capabilities"}
{"return": {}}
{ "execute": "blockdev-add",
   "arguments": { "options" : {
"id": "tc1",
"driver": "qcow2",
"file": { "driver": "file",
"filename": "test.qc2" } } } }

{"return": {}}
{ "execute": "device_add", "arguments": {
"driver": "virtio-blk-pci", "id": "vda", "drive": "tc1"  } }
{"return": {}}

Thanks!

Ken



--- Begin Message ---
Markus,

Nevermind my previous question, I see now that you add a scsi bus prior to 
adding the scsi disk.  

However, I did this and qmp returned {[]} in both cases and I am still not 
seeing the disk in the vm.


here's the qmp session:

{"execute":"qmp_capabilities"}
{"return": {}}
{ "execute": "blockdev-add",
   "arguments": { "options" : { 
"id": "tc1",
"driver": "qcow2",  
"file": { "driver": "file", 
"filename": "/home/kchiang/kvmimages/xpsp2_b-0012.qc2" } } } } 
{"return": {}}
{ "execute": "device_add", "arguments": {
"driver": "virtio-scsi-pci", "id": "vs-hba" } }
{"return": {}}
{ "execute": "device_add", "arguments": {
"driver": "scsi-disk", "id": "sdb", "drive": "tc1",
"bus": "vs-hba.0"  } }
{"return": {}}
{ "execute": "query-block" }
{"return": [{"io-status": "ok", "device": "ide0-hd0", "locked": false, 
"removable": false, "inserted": {"iops_rd": 0, "image": {"virtual-size": 
551872, "filename": "kvmimages/vts-6g-u12-inetsim.image", "format": "raw", 
"actual-size": 555968, "dirty-flag": false}, "iops_wr": 0, "ro": false, 
"backing_file_depth": 0, "drv": "raw", "iops": 0, "bps_wr": 0, "encrypted": 
false, "bps": 0, "bps_rd": 0, "file": "kvmimages/vts-6g-u12-inetsim.image", 
"encryption_key_missing": false}, "type": "unknown"}, {"io-status": "ok", 
"device": "ide1-cd0", "locked": false, "removable": true, "tray_open": false, 
"type": "unknown"}, {"device": "floppy0", "locked": false, "removable": true, 
"tray_open": false, "type": "unknown"}, {"device": "sd0", "locked": false, 
"removable": true, "tray_open": false, "type": "unknown"}, {"io-status": "ok", 
"device": "tc1", "locked": false, "removable": false, "inserted": {"iops_rd": 
0, "image": {"virtual-size": 5368709120, "filename": 
"/home/kchiang/kvmimages/xpsp2_b-0012.qc2", "cluster-size": 65536, 
"format": "qcow2", "actual-size": 1550454784, "format-specific": {"type": 
"qcow2", "data": {"compat": "0.10"}}, "dirty-flag": false}, "iops_wr": 0, "ro": 
false, "backing_file_depth": 0, "drv": "qcow2", "iops": 0, "bps_wr": 0, 
"encrypted": false, "bps": 0, "bps_rd": 0, "file": 
"/home/kchiang/kvmimages/xpsp2_b-0012.qc2", "encryption_key_missing": 
false}, "type": "unknown"}]}

am I missing anything else?

I've also tried rebooting the VM and running rescan-scsi-bus to no avail.

Ken

On Sat