Red Hat Bugzilla – Bug 616659
mrg buffers: migration breaks between systems with/without vhost
Last modified: 2013-01-09 17:54:50 EST
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
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.
move to verified based on comment#7
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.
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