Re: [libvirt] inconsistent handling of "qemu64" CPU model
On Wed, May 25, 2016 at 11:13:24PM -0600, Chris Friesen wrote:
[...]
However, if I explicitly specify a custom CPU model of
"qemu64" the
instance refuses to boot and I get a log saying:
[Not a direct answer to the exact issue you're facing, but a related
issue that is being investigated presently...]
Currently there's a related (regression) in upstream libvirt 1.3.4:
The crux of the issue here is: the libvirt custom 'gate64' model is not
being translated into a CPU definition that QEMU can recognize
(which you can find from `qemu-system-x86 -cpu \?`).
See this bug (it has reproducer, and discussion):
https://bugzilla.redhat.com/show_bug.cgi?id=1339680 -- libvirt CPU
driver fails to translate a custom CPU model into something that
QEMU recognizes
The bug (regression) is bisected, by Jiri Denemark, to this commit:
v1.2.9-31-g445a09b "qemu: Don't compare CPU against host for TCG".
libvirtError: unsupported configuration: guest and host CPU are not
compatible: Host CPU does not provide required features: svmlibvirtError:
unsupported configuration: guest and host CPU are not compatible: Host CPU
does not provide required features: svm
When this happens, some of the XML for the domain looks like this:
<os>
<type arch='x86_64'
machine='pc-i440fx-utopic'>hvm</type>
....
<cpu mode='custom' match='exact'>
<model fallback='allow'>qemu64</model>
<topology sockets='1' cores='1' threads='1'/>
</cpu>
Of course "svm" is an AMD flag and I'm running an Intel CPU. But why does
it work when I just rely on the default virtual CPU? Is
kvm_default_unset_features handled differently when it's implicit vs
explicit?
If I explicitly specify a custom CPU model of "kvm64" then it boots, but of
course I get a different virtual CPU from what I get if I don't specify
anything.
Following some old suggestions I tried turning off nested kvm, deleting
/var/cache/libvirt/qemu/capabilities/*, and restarting libvirtd. Didn't
help.
So...anyone got any ideas what's going on? Is there no way to explicitly
specify the model that you get by default?
Thanks,
Chris
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