[libvirt] CPU compare and baseline

[Daniel P. Berrange]

On Mon, Mar 21, 2011 at 06:34:40PM +0100, Edouard Thuleau wrote:
> Hi,
> I try to understand the compare and baseline CPU commands with libvirt.
> This functions are useful for the migration ? Before migrate a domain to
> other host, libvirt verifies the CPU compatibility, that's right ?
> 
> I've got two 64bits hosts, one with an Intel CPU :

[snip]

> But if I try to migrate a domain from a host to another, the CPU compare
> says there are incompatible.
> I don't understand, I've done live migration manually (*migrate -d tcp:
> 192.168.1.10:4444*) with KVM and it's works nicely. Why it's not possible
> trough libvirt ?

You have left out the one important piece of information...

What is the <cpu> block configured for your *guest* XML.
I expect that your guest XML has set an explicit vendor
model name, and so libvirt will be refusing to migrate
from Intel to AMD even though the flags look compatible.

You can use the 'virsh cpu-compare' command, giving it the <cpu>
XML from your *guest*, and it will tell you if it is compatible
with that host.

Daniel
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