Re: [libvirt-users] os/type/machine/pc-xxxx meaning ? following live migration issue after an upgrade

On Fri, Jul 04, 2014 at 11:04:53AM +0200, Benoit Rousselle wrote: > Dear All, > > I have upgrade my hypervisors: > qemu-kvm 0.12.5 => 1.1.2 > libvirt-bin 0.8.3-5 => 0.9.12.3 > (debian6 to debian7) > > After that upgrade, i noticed that live migration was most of the time > failing (freeze) (not always) > I also noticed that creating a machine with the updated hypervisor was > always working. > > After some days of investigation mainly on network side, i found this > setting that seems to fix the issue in the xml: > > <os> > <type arch='x86_64' machine='pc-0.12'>hvm</type> > <boot dev='hd'/> > </os> > > replacing pc-0.12 with pc-1.1 seems to fix the issue. > > Here are my questions : > 1) what is the meaning/purpose of that setting ? (i guess it is somehow > linked to the version of kvm ;) ) It encodes a specific guest machine ABI. > 2) can i just change it in all xmls ? ( i have plenty of linux/windows > flavors running in my vms) If you change it, the guest machine ABI will have changes. Usually fairly minor, but changes none the less. This is not a problem for most guest OS. Sometimes though, a change will be enough to cause Windows to want todo license re-activation. > 3) is it possible to put a more generic value? So we don't have the same > issue on next upgrade. We use a fixed version in an attempt to prevent windows re-activation. > 4) Is there a script/doc that explains what needs to be done on the vm > itself (xml or other) when we upgrade libvirt/kvm ? Not really. If you don't mind the risk of Windows re-activation then just delete the machine attribute and libvirt will re-add it using the newest machine type version. Regards, Daniel