[libvirt-users] setvcpus --guest on windows

Thomas Stein himbeere at meine-oma.de
Wed Nov 5 13:49:12 UTC 2014

Am 05.11.14 14:44, schrieb Eric Blake:
> On 11/05/2014 10:50 AM, Thomas Stein wrote:
>> Am 04.11.14 17:55, schrieb Thomas Stein:
>>> Hello.
>>> Just a quick question. Is "setvcpus $windowsVM --guest 4" supposed to
>>> work? I have qemu-guest-agent (1.6.something) running inside a windows7
>>> vm but all i get is:
>>> virsh # setvcpus windows7 --guest 4
>>> error: invalid argument: requested vcpu count is greater than the count
>>> of enabled vcpus in the domain: 4 > 1
> I'm not exactly sure how well setvcpus --guest will work (or not) with
> windows guests.  But the way it works for Linux guest is by telling the
> guest to treat an available cpu as offline; for this to work, the host
> must provide that cpu.  So the error message makes sense.
>>> The xml file looks like this:
>>> <vcpu placement='static' current='1'>4</vcpu>
> For --guest to have any chance of changing cpus from the guest
> perspective, you need something like <vcpu current='4'>4</vcpu> as your
> starting point, then tell the guest to offline 3 cpus shortly after
> boot, then later tell the guest to turn the cpus back on when you are
> ready to give it more power.

Okay. Now i understand. Thanks.

>> Another question regarding qemu-guest-agent. What if i have more then
>> one VM running on a host? Is the configuration for any of them the same
>> or do i have to adjust some settings?
>>     <channel type='unix'>
>>       <source mode='bind' path='/var/lib/libvirt/qemu/f16x86_64.agent'/>
>>       <target type='virtio' name='org.qemu.guest_agent.0'/>
>>       <address type='virtio-serial' controller='0' bus='0' port='1'/>
>>     </channel>
>> I mean, do i have to use a different port or something for each VM?
> The <address> element of a guest XML is related to what the _guest_
> sees, not what the host provides.  So it is perfectly fine for multiple
> guests to see the same <address> (each sees their own virtual hardware,
> and could care less if some other guest has similar virtual hardware).
> Similarly for the name of the <target> element - each guest will see
> their own guest-agent channel at the name 'org.qemu.guest_agent.0'; this
> is a guest view, so it doesn't matter whether other guests happen to
> also pick the same name.

Very understandable too. Thank you again.


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