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Bug 725625 - Hot unplug one virtio balloon device cause another balloon device unavailable
Summary: Hot unplug one virtio balloon device cause another balloon device unavailable
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: qemu-kvm
Version: 6.2
Hardware: Unspecified
OS: Unspecified
medium
medium
Target Milestone: rc
: ---
Assignee: Amit Shah
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2011-07-26 06:30 UTC by Qunfang Zhang
Modified: 2013-01-10 00:09 UTC (History)
9 users (show)

Fixed In Version: qemu-kvm-0.12.1.2-2.179.el6
Doc Type: Bug Fix
Doc Text:
It was possible to expose multiple balloon devices to the guest. This could cause undefined behaviour when the various balloon devices were given different commands. The fix is to not allow more than one balloon device.
Clone Of:
Environment:
Last Closed: 2011-12-06 15:54:36 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2011:1531 0 normal SHIPPED_LIVE Moderate: qemu-kvm security, bug fix, and enhancement update 2011-12-06 01:23:30 UTC

Description Qunfang Zhang 2011-07-26 06:30:27 UTC 
Description of problem:
Boot guest with 2 virtio balloon devices, and then balloon the memory to a smaller value, it works. Then hot unplug one virtio balloon device, something unexpected happens:
(1) For windows guest, balloon value will change to the original as configured in qemu command line. Then ballooning the memory to another value, nothing changes.
(2) For RHEL guest, balloon the memory from 2048 to 2000 for example. And then hot unplug one virtio balloon device and leave another one. Checked the memory, it is still 2000M. Then ballooning the memory to a new one, such as 1900(M), nothing happens.

Version-Release number of selected component (if applicable):
kernel-2.6.32-171.el6.x86_64
qemu-kvm-0.12.1.2-2.171.el6.x86_64

How reproducible:
Always

Steps to Reproduce:
1.Boot a guest with two virtio balloon devices:
/usr/libexec/qemu-kvm -m 16G -smp 4 -cpu cpu64-rhel6,+x2apic -usbdevice tablet -drive file=win7-64-virtio.qcow2,format=qcow2,if=none,id=drive-ide0-0-0,werror=stop,rerror=stop,cache=none -device virtio-blk-pci,drive=drive-ide0-0-0,id=ide0-0-0 -netdev tap,id=hostnet0,script=/etc/qemu-ifup -device e1000,netdev=hostnet0,mac=00:10:1a:20:06:28,bus=pci.0,addr=0x6 -boot dc -uuid bea9c85e-0a47-4030-979d-5d94bb3d6161 -rtc-td-hack -no-kvm-pit-reinjection -monitor stdio -qmp tcp:0:4444,server,nowait -name win7-64-balloon -spice disable-ticketing,port=5931 -vga qxl -device virtio-balloon-pci,bus=pci.0,id=balloon0 -device virtio-balloon-pci,bus=pci.0,id=balloon1

2.{"execute":"query-balloon"}
{"return": {"actual": 17179869184}}

{"execute":"balloon","arguments":{"value":16106127360}}
{"return": {}}

{"execute":"query-balloon"}
{"return": {"actual": 16552820736}}

{"execute":"query-balloon"}
{"return": {"actual": 16106127360}}


3. Hot unplug one virtio balloon device.

{"execute":"device_del","arguments":{"id":"balloon1"}}
{"return": {}}

4. Check the memory
{"execute":"query-balloon"}
{"return": {"actual": 17179869184}}

{"execute":"query-balloon"}
{"return": {"actual": 17179869184}}

5. {"execute":"balloon","arguments":{"value":16106127360}}
{"return": {}}

{"execute":"query-balloon"}
{"return": {"actual": 17179869184}}

  
Actual results:
Hot unplug one virtio balloon device cause another balloon device unavailable

Expected results:
Another virtio balloon device should work after hot unplug the first one.

Additional info:
Comment 2 Amit Shah 2011-08-01 11:44:25 UTC 
Multiple balloon devices don't make sense.  This will be fixed by making sure we cannot hot-plug more than one balloon device.
Comment 7 FuXiangChun 2011-08-18 09:30:37 UTC 
verify on qemu-kvm-0.12.1.2-2.182.el6.x86_64
kernel 2.6.32-189.el6.x86_64

steps to verification
1.# /usr/libexec/qemu-kvm -enable-kvm -m 6G -smp 4 -name rhel6 -uuid ddcbfb49-3411-1701-3c36-6bdbc00bedb9 -rtc base=utc,clock=host,drdev/migrate/data3,if=none,id=drive-ide0-0-0,boot=on,format=qcow2,cache=none -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,physical_block_size=4096,logical_block_size=4096 -netdev tap,id=hostnet0 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:50:a4:c2:c2 -chardev pty,id=serial0 -device isa-serial,chardev=serial0 -usb -device usb-tablet,id=input0 -spice id=on,disable-ticketing,port=5911 -monitor stdio -device virtio-balloon-pci,bus=pci.0,id=balloon0 -device virtio-balloon-pci,bus=pci.0,id=balloon1

actual result:
qemu-kvm: -device virtio-balloon-pci,bus=pci.0,id=balloon1: Another balloon device already registered
qemu-kvm: -device virtio-balloon-pci,bus=pci.0,id=balloon1: Device 'virtio-balloon-pci' could not be initialized

2./usr/libexec/qemu-kvm -enable-kvm -m 6G -smp 4 -name rhel6 -uuid ddcbfb49-3411-1701-3c36-6bdbc00bedb9 -rtc base=utc,clock=host,drdev/migrate/data3,if=none,id=drive-ide0-0-0,boot=on,format=qcow2,cache=none -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,physical_block_size=4096,logical_block_size=4096 -netdev tap,id=hostnet0 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:50:a4:c2:c2 -chardev pty,id=serial0 -device isa-serial,chardev=serial0 -usb -device usb-tablet,id=input0 -spice id=on,disable-ticketing,port=5911 -monitor stdio -device virtio-balloon-pci,bus=pci.0,id=balloon0 

3.(qemu) device_del balloon0

actual result:

can not delete balloon device from monitor

base on above result.  this bug has been fixed.
Comment 8 langfang 2011-09-01 03:04:44 UTC 
Reproduced this issue with qemu-kvm-0.12.1.2-2.178.el6.x86_64,kernel
2.6.32-171.el6.x86_64:
Steps:
1)boot guest with two balloons
-device virtio-balloon-pci,bus=pci.0,id=balloon0 -device
virtio-balloon-pci,bus=pci.0,id=balloon1
2)(qemu)info balloon
balloon: actual=3000
3)Hot unplug one virtio balloon device:
(qemu)device_del balloon1
4)(qemu) balloon 2900
5)(qemu) info balloon
   balloon: actual=3000

Result: The balloon device does not function well after hot unplug
another balloon.


Verified pass on qemu-kvm-0.12.1.2-2.184.el6.x86_64,kernel
2.6.32-191.el6.x86_64:
I test 3 scenarios:

1)boot guest with two balloons
Result: QEMU gives the friendly prompts:
qemu-kvm: -device virtio-balloon-pci,bus=pci.0,id=balloon1: Another
balloon device already registered
qemu-kvm: -device virtio-balloon-pci,bus=pci.0,id=balloon1: Device
'virtio-balloon-pci' could not be initialized


2)boot guest with one balloon, and then hot plug the second one:
(qemu)device_add driver=virtio-balloon-pci,id=balloon2

Result: QEMU gives the friendly tip:
Another balloon device already registered
Device 'virtio-balloon-pci' could not be initialized
(qemu)

3)Boot guest with none balloon and then hot plug 2 balloon devices:

(qemu)device_add driver=virtio-balloon-pci,id=balloon1
(qemu)device_add driver=virtio-balloon-pci,id=balloon2

Results: Can not hot plug the 2nd balloon, QEMU gives the friendly tip:
Another balloon device already registered
Device 'virtio-balloon-pci' could not be initialized


So, According to Amit's patch, don't allow multiple balloon handler
registrations.
this bug is verified pass.
Comment 10 Amit Shah 2011-11-18 12:08:32 UTC 
    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
It was possible to expose multiple balloon devices to the guest.  This could cause undefined behaviour when the various balloon devices were given different commands.  The fix is to not allow more than one balloon device.
Comment 11 errata-xmlrpc 2011-12-06 15:54:36 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2011-1531.html
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