Am 05.11.14 11:48, schrieb Martin Kletzander:> On Wed, Nov 05, 2014 at 11:35:37AM +0100, Thomas Stein wrote: >>Hello. >> >>I'm struggeling a little bit with the setvcpus command. I'm trying now >>to get this running for a linux VM. Here is what i have: >> >> <vcpu placement='auto' current='2'>4</vcpu> >> >>Now the VM is starting with 2 CPUs. When i try to increase the number of >>CPUs i get: >> >>setvcpus dev --guest 4 >>error: invalid argument: requested vcpu count is greater than the count >>of enabled vcpus in the domain: 4 > 2 >> > > This sets the current number of cpus and that cannot be changed liveI'm not quite sure i understand what you mean. What would be a common use case for this setting? <vcpu placement='auto' current='2'>4</vcpu>> (unless you have cpu hot(un)plug).What is neccessary to have that? thanks and cheers t.>>Strange thing is when i set in the xml file: >> >> <vcpu placement='auto' current='4'>4</vcpu> >> >>the VM starts with 4CPUs and setting the CPUs works. >> > > Because the max is 4 and you're setting the "current" number. > >>I can do: >> >>setvcpus dev --guest 2 >> >>and: >> >>setvcpus dev --guest 4 >> >>Is this a bug? Should i try to upgrade to 1.2.10? There seem to be a lot >>of changes in it regarding setvcpus. >> >>thanks and cheers >>t. >> >>_______________________________________________ >>libvirt-users mailing list >>libvirt-users@redhat.com >>https://www.redhat.com/mailman/listinfo/libvirt-users >
On 11/05/2014 01:20 PM, Thomas Stein wrote:> Am 05.11.14 11:48, schrieb Martin Kletzander: >> On Wed, Nov 05, 2014 at 11:35:37AM +0100, Thomas Stein wrote: >>> Hello. >>> >>> I'm struggeling a little bit with the setvcpus command. I'm trying now >>> to get this running for a linux VM. Here is what i have: >>> >>> <vcpu placement='auto' current='2'>4</vcpu>This is one case where xen may be a bit more powerful than current qemu support. Xen supports booting a guest with a promise of a maximum cpu larger than what it boots with; but I don't know that qemu does that well yet. For now, with qemu, you pretty much have to boot with all cpus enabled, then after the guest is up and running, disable the cpus you don't plan to use right away. CPU hotplug/hot-unplug is still a work in progress in qemu (for example, some versions of qemu support hotplug but not hot-unplug). I haven't played much with it myself to know what minimum version of libvirt and qemu will do what you want, so you may have to do some experimentation. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
Am 05.11.14 14:48, schrieb Eric Blake:> On 11/05/2014 01:20 PM, Thomas Stein wrote: >> Am 05.11.14 11:48, schrieb Martin Kletzander: >>> On Wed, Nov 05, 2014 at 11:35:37AM +0100, Thomas Stein wrote: >>>> Hello. >>>> >>>> I'm struggeling a little bit with the setvcpus command. I'm trying now >>>> to get this running for a linux VM. Here is what i have: >>>> >>>> <vcpu placement='auto' current='2'>4</vcpu> > > This is one case where xen may be a bit more powerful than current qemu > support. Xen supports booting a guest with a promise of a maximum cpu > larger than what it boots with; but I don't know that qemu does that > well yet. For now, with qemu, you pretty much have to boot with all > cpus enabled, then after the guest is up and running, disable the cpus > you don't plan to use right away. CPU hotplug/hot-unplug is still a > work in progress in qemu (for example, some versions of qemu support > hotplug but not hot-unplug). I haven't played much with it myself to > know what minimum version of libvirt and qemu will do what you want, so > you may have to do some experimentation.Thanks. I let you know if my experiments lead to some discoveries. cheers t.