On Tue, Jan 09, 2018 at 04:37:10PM +0100, Jiri Denemark wrote:
On Tue, Jan 09, 2018 at 15:32:54 +0100, Kashyap Chamarthy wrote:
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But doesn't tell *what* the default value is. It is check='partial'. Mention it so.
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NACK
As I said on IRC, the default differs with guest architecture ('partial' for x86_64, 'none' for all others).
Yep, I missed to distinguish that detail.
Moreover this only applies to QEMU driver. Oh and it even changes based on the mode attribute to make not make it easy. But this is really an implementation detail. Libvirt will just use a suitable default to stay compatible with older releases.
That's all good. If you think nothing needs to be clarified here, that's OK. (Some admins who operate a lot of VMs with libvirt will disagree with you, though.) And as we saw on IRC, `virt-install` muddies the water in this case by gratuitously adding a CPU parameter with check='full' (even if a user didn't explicitly specify it) when you simply import an image and look at the run-time guest XML: $> virt-install --name vm1 --ram 2048 \ --disk path=./vm1.qcow2,format=qcow2 --nographics \ --import --os-variant fedora27 $> virsh dumpxml vm1 | grep check <cpu mode='custom' match='exact' check='full'> (You might, fairly, argue here that: "Well, that's a bug in `virt-install`, go complain there.") It all comes across as messy to an unsuspecting admin. (If a competent admin finds it confusing, good luck to new admins who want to wrap their head around this.) - - - Background for others reading: The admin who reported this was confused when he was creating guests with `virt-install`, which adds check='full' (as noted earlier), and the guest throws: error: Failed to start domain foo.org error: operation failed: guest CPU doesn't match specification: extra features: vme,arat So "somehow" QEMU added the CPU features 'vme' and 'arat' by itself, now you have to specify them in libvirt. So the admin ended up with a `sed` one-liner that updates the guest XML with the missing features: sed -i -e "s-</cpu>-<feature policy='require' name='vme'/></cpu>-" sed -i -e "s-</cpu>-<feature policy='require' name='arat'/></cpu>-" Versions: libvirt 3.2 and QEMU 2.9