Host cpu_match attr is ignored if Global cpu_mode attr is set

[tcooper]

If the global attribute, cpu_mode, is set then the host attribute, cpu_match, is ignored/overwritten when generating the libvirt XML configuration for a KVM guest.

• List the default cpu related attributes for a KVM guest (set here)...

[root@cluster config]# rocks list host attr vcn-1-11 | egrep "cpu_m"
vcn-1-11: cpu_mode      host-passthrough                                               G

• Report the default XML configuration for a KVM guest...

[root@cluster config]# rocks report host vm config vcn-1-11 | grep "cpu mode" -B1 -A1
  <vcpu>24</vcpu>
  <cpu mode='host-passthrough'/>
  <cputune>

• Add a host cpu_match attribute to the KVM guest...

[root@cluster config]# rocks add host attr vcn-1-11 cpu_match \
    value="host-passthrough:<topology sockets='2' cores='12' threads='1'/>"

• List host attributes of the KVM guest...

[root@cluster config]# rocks list host attr vcn-1-11 | egrep "cpu_m"
vcn-1-11: cpu_match     host-passthrough:<topology sockets='2' cores='12' threads='1'/> 
                                                                                       H
vcn-1-11: cpu_mode      host-passthrough                                               G

• Report the libvirt XML configuration of the KVM guest...

[root@cluster config]# rocks report host vm config vcn-1-11 | grep "cpu mode" -B1 -A1
  <vcpu>24</vcpu>
  <cpu mode='host-passthrough'/>
  <cputune>

NOTE: The topology configuration is not there.

• Remove global cpu_mode attribute

[root@cluster config]# rocks remove attr cpu_mode

• List host attributes of the KVM guest...

[root@cluster config]# rocks list host attr vcn-1-11 | egrep "cpu_m"
vcn-1-11: cpu_match     host-passthrough:<topology sockets='2' cores='12' threads='1'/>
                                                                                       H

• Report xml config of the KVM guest...

[root@cluster config]# rocks report host vm config vcn-1-11 | grep "cpu mode" -B1 -A2
  <vcpu>24</vcpu>
  <cpu mode='host-passthrough'>
<topology sockets='2' cores='12' threads='1'/>
  </cpu>

NOTE: The topology configuration is now reported

[lclementi]

On Sat, Dec 20, 2014 at 8:00 PM, Trevor Cooper [email protected] wrote:

If the global attribute, cpu_mode, is set then the host attribute, cpu_match, is ignored/overwritten when generating the libvirt XML configuration for a KVM guest.

List the default cpu related attributes for a KVM guest (set here)...

[root@cluster config]# rocks list host attr vcn-1-11 | egrep "cpu_m"
vcn-1-11: cpu_mode host-passthrough G

Report the default XML configuration for a KVM guest...

[root@cluster config]# rocks report host vm config vcn-1-11 | grep "cpu mode" -B1 -A1
24

Add a host cpu_match attribute to the KVM guest...

[root@cluster config]# rocks add host attr vcn-1-11 cpu_match
value="host-passthrough:"

List host attributes of the KVM guest...

[root@cluster config]# rocks list host attr vcn-1-11 | egrep "cpu_m"
vcn-1-11: cpu_match host-passthrough:
H
vcn-1-11: cpu_mode host-passthrough G

Report the libvirt XML configuration of the KVM guest...

[root@cluster config]# rocks report host vm config vcn-1-11 | grep "cpu mode" -B1 -A1
24

NOTE: The topology configuration is not there.

Remove global cpu_mode attribute

[root@cluster config]# rocks remove attr cpu_mode

List host attributes of the KVM guest...

[root@cluster config]# rocks list host attr vcn-1-11 | egrep "cpu_m"
vcn-1-11: cpu_match host-passthrough:
H

Report xml config of the KVM guest...

[root@cluster config]# rocks report host vm config vcn-1-11 | grep "cpu mode" -B1 -A2
24

NOTE: The topology configuration is now reported

That's somehow expected.

The cpu_mode has precedence over the cpu_match, and it doesn't matter
if attributes are declared with global, appliance, or host scope the
one which wins count.

In your case since you have both cpu_match and cpu_mode declared :

[root@cluster config]# rocks list host attr vcn-1-11 | egrep "cpu_m"
vcn-1-11: cpu_match host-passthrough: H
vcn-1-11: cpu_mode host-passthrough
G

cpu_mode wins and set the cpu tag.

I think we can make this a little easier and leave some of the
(useless) complexity out.

My idea is to leave only 1 attribute (let's say cpu_mode) then if its
value does not contain a colon, nothing change (it works exactly like
now) if there is a colon it will behave like cpu_match does now.
So at least we have only 1 attribute to think about and the
documentation gets also easier.

What do you think? Does it sounds easier to you?

Luca

[tcooper]

Can't think of any down-sides as this isn't in production anywhere yet...

• Easy application 👍
• Solves problem 👍
• Makes documentation easier 👍

I'd say add it before release of 6.2 if at all possible.

[lclementi]

4c123a0

fixed