for some reason, neither virt-manager nor virsh will allow you to change the number of cpus or memory allocated to kvm guests. virt-manager: You can pull up the details page, make changes and hit 'apply'. Nothing happens. If you close the details window and re-open it all values are back to their old settings. virsh: virsh # setvcpus fedora8-x86_64 4 libvir: error : this function is not supported by the hypervisor: virDomainGetMaxVcpus virsh # setmaxmem fedora8-x86_64 1024000 libvir: error : this function is not supported by the hypervisor: virDomainSetMaxMemory error: Unable to change MaxMemorySize While kvm doesn't support changing these on a running guest, it should allow you to do so on a inactive guest. (At least I think thats the case, it would be lovely to change them on the fly too if possible). Manually editing the guests xml file and restarting libvirt gets the new values working fine.
Just retested this on F9. setvcpus seems to behave the same. setmaxmem seems to now accept the values, but it's not reflected in dumpxml or the guest. :(
*** Bug 441653 has been marked as a duplicate of this bug. ***
*** Bug 444206 has been marked as a duplicate of this bug. ***
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Same retesting from comment #1, still happens in f10.
I'm the reporter of 441653, a duplicate for this one. Now that I made a reinstall (not upgrade) fc9 -> fc10, cpu setting works for me.
Sorry about the lack of communication on this issue, I did the original dupes and thought I updated the bug with status info, but I didn't :( Apologies. Since libvirt 0.4.6, libvirt reports the correct max vcpu value for KVM. Since a while before that, the setvcpu and setmem/maxmem commands have been hooked up, so this bug is fully resolved. 0.5.0 is now in F9 and F10. Kevin, in regards to Comment #1 and Comment #6, none of these commands will take effect on a running VM. That is a separate issue though: I don't think cpu hotplug is supported for kvm yet, though memory hotplug/ballooning is (I think), but we don't support it in libvirt. Please file a separate bug for those issues. Closing as CURRENTRELEASE.