On Fri, Oct 10, 2014 at 03:42:41PM +0530, Prerna Saxena wrote:
From 7228aacaa4b24907b1cbf33838ada8fb81890419 Mon Sep 17 00:00:00 2001 From: Prerna Saxena <prerna@linux.vnet.ibm.com> Date: Tue, 7 Oct 2014 10:53:08 +0530
PowerISA allows processors to run VMs in binary compatibility ("compat") mode supporting an older version of ISA. QEMU has recently added support to explicitly denote a VM running in compatibility mode through commit 6d9412ea & 8dfa3a5e85. Now, a "compat" mode VM can be run by invoking this qemu commandline on a POWER8 host: -cpu host,compat=power7.
If this is using 'host'
This patch allows libvirt to extend the "fallback" semantics of cpu model to describe this new mode for PowerKVM guests. As an example: When a user wants to request a power7 vm to run in compatibility mode on a Power8 host, this can be described in XML as follows : <cpu mode='custom' match='exact'> <model fallback='compat'>power7</model> </cpu>
Then I don't think this should be using mode='custom', but rather it should be 'host-passthrough'. We would use the <model> to denote the compatibility mode for the host passthrough. IOW, it feels like this is better described as <cpu mode='host-passthrough' match='exact'> <model>power7</model> </cpu> Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|