[libvirt] CPU compare and baseline

[Edouard Thuleau]

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 :

> *<cpu>*

* **<arch>x86_64</arch>*

* **<model>Penryn</model>*

* **<vendor>Intel</vendor>*

* **<topology sockets='1' cores='2' threads='1'/>*

* **<feature name='xtpr'/>*

* **<feature name='tm2'/>*

* **<feature name='est'/>*

* **<feature name='vmx'/>*

* **<feature name='ds_cpl'/>*

* **<feature name='monitor'/>*

* **<feature name='pbe'/>*

* **<feature name='tm'/>*

* **<feature name='ht'/>*

* **<feature name='ss'/>*

* **<feature name='acpi'/>*

* **<feature name='ds'/>*

* **<feature name='vme'/>*

*</cpu>*


and one with an AMD CPU

> *<cpu>*

* **<arch>x86_64</arch>*

* **<model>Opteron_G2</model>*

* **<vendor>AMD</vendor>*

* **<topology sockets='1' cores='2' threads='1'/>*

* **<feature name='3dnowprefetch'/>*

* **<feature name='cr8legacy'/>*

* **<feature name='extapic'/>*

* **<feature name='cmp_legacy'/>*

* **<feature name='3dnow'/>*

* **<feature name='3dnowext'/>*

* **<feature name='fxsr_opt'/>*

* **<feature name='mmxext'/>*

* **<feature name='ht'/>*

* **<feature name='vme'/>*

*</cpu>*


Baseline output :
AMD to intel:

> *$ virsh cpu-baseline cpu_gargamel.xml *

*<cpu match='exact'>*

*  <model>Opteron_G2</model>*

*  <vendor>AMD</vendor>*

*  <feature policy='require' name='3dnowprefetch'/>*

*  <feature policy='require' name='cr8legacy'/>*

*  <feature policy='require' name='extapic'/>*

*  <feature policy='require' name='cmp_legacy'/>*

*  <feature policy='require' name='3dnow'/>*

*  <feature policy='require' name='3dnowext'/>*

*  <feature policy='require' name='fxsr_opt'/>*

*  <feature policy='require' name='mmxext'/>*

*  <feature policy='require' name='ht'/>*

*  <feature policy='require' name='vme'/>*

*</cpu>*


Intel to AMD:

> *$ virsh cpu-baseline cpu_azrael.xml *

*<cpu match='exact'>*

*  <model>Penryn</model>*

*  <vendor>Intel</vendor>*

*  <feature policy='require' name='xtpr'/>*

*  <feature policy='require' name='tm2'/>*

*  <feature policy='require' name='est'/>*

*  <feature policy='require' name='vmx'/>*

*  <feature policy='require' name='ds_cpl'/>*

*  <feature policy='require' name='monitor'/>*

*  <feature policy='require' name='pbe'/>*

*  <feature policy='require' name='tm'/>*

*  <feature policy='require' name='ht'/>*

*  <feature policy='require' name='ss'/>*

*  <feature policy='require' name='acpi'/>*

*  <feature policy='require' name='ds'/>*

*  <feature policy='require' name='vme'/>*

*</cpu>*


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 ?

I use libvirt 0.7.5 with KVM on an Ubuntu LTS 10.04.

Regards,
Doude.
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