Bug 773032

Summary: make sure xen-netfront defaults to copying
Product: Red Hat Enterprise Linux 7 Reporter: Laszlo Ersek <lersek>
Component: kernelAssignee: Xen Maintainance List <xen-maint>
Status: CLOSED NOTABUG QA Contact: Virtualization Bugs <virt-bugs>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 7.0CC: bfan, drjones, leiwang, qwan, wshi
Target Milestone: rc   
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Hardware: Unspecified   
OS: Unspecified   
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Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2013-11-26 14:20:00 UTC Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Laszlo Ersek 2012-01-10 17:48:54 UTC 
Upstream is working on reintroducing flipping to netback:

http://lists.xen.org/archives/html/xen-devel/2012-01/msg00557.html

Presumably they will re-enable flipping in xen-netfront as well once the above effort is complete. We should make sure that a RHEL-7 xen domU still uses copying (at least in combination with a RHEL-5 dom0). There seem to be two possibilities: (a) change the host side to advertise lack of flipping support (ie. only copying available), (b) make the guest ask for copying per default.

Option (b) was chosen for the RHEL-4 and RHEL-5 domU. RHEL-6 xen-netfront doesn't support flipping at all. We could choose (b) for the RHEL-7 guest again (if by the time of final forking xen-netfront will have flipping enabled at all), or try to cover it once for all in the host (option (a)). The latter could cause more regressions FWIW, Paolo mentions problems with migration.

This BZ is filed for option (b).
Comment 1 Laszlo Ersek 2012-01-12 14:35:15 UTC 
http://lwn.net/Articles/474791/