Bug 616659

Summary: mrg buffers: migration breaks between systems with/without vhost
Product: Red Hat Enterprise Linux 6 Reporter: Michael S. Tsirkin <mst>
Component: qemu-kvmAssignee: jason wang <jasowang>
Status: CLOSED ERRATA QA Contact: Virtualization Bugs <virt-bugs>
Severity: medium Docs Contact:
Priority: medium    
Version: 6.1CC: bcao, ddumas, ehabkost, llim, michen, mjenner, mkenneth, snagar, tburke, virt-maint
Target Milestone: beta   
Target Release: 6.1   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: qemu-kvm-0.12.1.2-2.129.el6 Doc Type: Bug Fix
Doc Text:
Cause: vhost_net does not have the feature of mergeable buffer. Consequence: Migrate a guest from src with userspace backend to a dest with vhost_net backend would break. Fix: Add the support of mergeable buffer support to vhost_net. Result: Migrate between userspace virtio-net and vhost_net backend would not fail.
 Story Points: ---
Clone Of:
: 616660 (view as bug list) Environment:
Last Closed: 2011-05-19 11:28:46 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 580951, 616660    

Description Michael S. Tsirkin 2010-07-21 04:53:38 UTC 
Description of problem:
vhost transparently disables mergeable buffers flag.
This causes migration to fail if it is attempted between
systems with/without this flag set.

Version-Release number of selected component (if applicable):
qemu-kvm-0.12.1.2-2.90.el6.x86_64

How reproducible:
always

Steps to Reproduce:
1. on system A remove vhost_net module
2. on system B leave it in
3. start qemu with virtio-net
4. attempt migration B->A
  
Actual results:
migration fails

Expected results:
migration passes
Comment 7 Mike Cao 2011-01-13 09:32:29 UTC 
note :should   migration from vhost off to vhost on
reproduced on
# uname -r
2.6.32-92.el6.x86_64
# rpm -q qemu-kvm
qemu-kvm-0.12.1.2-2.90.el6.x86_64

Actual Result:
Features 0x100fffe3 unsupported. Allowed features: 0x511f7fe3
load of migration failed


Verified on 
# uname -r
2.6.32-94.el6.x86_64
# rpm -q qemu-kvm
qemu-kvm-0.12.1.2-2.129.el6.x86_64

Actual result:
After migration ,guest works well.

Base on above ,this issue has been fixed already.
Comment 11 Miya Chen 2011-03-09 05:03:26 UTC 
move to verified based on comment#7
Comment 12 jason wang 2011-05-05 09:52:28 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:
Cause: vhost_net does not have the feature of mergeable buffer.

Consequence: Migrate a guest from src with userspace backend to a dest with vhost_net backend would break.

Fix: Add the support of mergeable buffer support to vhost_net.

Result: Migrate between userspace virtio-net and vhost_net backend would not fail.
Comment 13 errata-xmlrpc 2011-05-19 11:28:46 UTC 
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2011-0534.html
Comment 14 errata-xmlrpc 2011-05-19 12:46:32 UTC 
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2011-0534.html