[libvirt-users] LibVirt query CPU Model support and restore operation

[Martin Kletzander]

On Tue, Jan 24, 2017 at 04:21:14PM +0530, akhilesh rawat wrote:
>hi,
>
>yes we are talking about same host here.
>
>You could've just used -cpu host-model-only
>>> I dont want to host model ( it is working with host model) .
>
>AS KVM seems to allow support Haswell with native commands . Does this mean
>in my case KVM is allowing software emulated cpu model.
>

I don't remember if it gets emulated or just dropped.  Do you remember
if you saw those in /proc/cpuinfo in the guest?  Maybe QEMU just dropped
them on startup.  I believe that was why we added the code that checks
for it.

>Can libvirt allow  software-emulated for non host model ?  if yes how .
>

You can force each feature, that way it could work, but I'm not sure
with all the refactoring that was there.

>thanks
>
>
>
>
>
>On Tue, Jan 24, 2017 at 1:32 PM, Martin Kletzander <mkletzan at redhat.com>
>wrote:
>
>> On Tue, Jan 24, 2017 at 10:08:12AM +0530, akhilesh rawat wrote:
>>
>>> Hello ,
>>>
>>> It was working good working with kvm management tools using libvirt .
>>> virsh/virt-manager .
>>>
>>> But then i got annoyed when management tool did not allow me to change the
>>> CPU model while creating new virtual machine .
>>> error
>>>
>>>
>> Are we talking about the same host?
>>
>> root at kvm-server qemu]# virt-install --virt-type kvm --name compute-2 --cpu
>>> Haswell-noTSX --ram=61440 --vcpus=20 --os-type=linux --os-variant=generic
>>> --disk
>>> compute2-disk0.qcow2,device=disk,bus=ide,size=300,sparse=tru
>>> e,format=qcow2
>>> --pxe --network bridge=virbr0,model=e1000 --network
>>> bridge=virbr0,model=e1000 --network bridge=virbr0,model=virtio --network
>>> bridge=virbr0,model=virtio --graphics vnc,port=5906 --noautoconsole
>>>
>>> Starting install...
>>> ERROR    unsupported configuration: guest and host CPU are not compatible:
>>> Host CPU does not provide required features: invpcid, erms, bmi2, smep,
>>> avx2, bmi1, fsgsbase, movbe, fma
>>> Domain installation does not appear to have been successful.
>>>
>>> I could not resolve this error .
>>>
>>>
>> You could've just used -cpu host-model-only.
>>
>> Finally i came across the post which say that libvirt cross verifies  flags
>>> under CPU model present in
>>> /usr/share/libvirt/cpu_map.xml and cat /proc/cpuinfo .
>>>
>>> An yes the flag complained were not present in host proc/cpuinfo.
>>>
>>> Question 1: Is it really needed for Libvirt to do this check .
>>>
>>>
>> It is, otherwise users might not get what they asked for.  Or it might
>> be software-emulated.
>>
>> AS KVM seems to allow support Haswell with native commands . Why libvirt is
>>> doing this check then ?
>>>
>>> As i was not sure where the problem lies and i was using libvirt 2.0.0
>>> version i upgraded to 2.5.0 by compiling form source .
>>> But then i faces issue using virsh/virt-manager as seem it was not
>>> compatilble with upgarded version of libvirt.
>>>
>>> Now my system is little messed  around libvirt . I did reinstall/reboot
>>> Quite many things not working .
>>>
>>> Question 2 : How can i restore original Libvirt 2.0.0 .
>>>
>>>
>> Depends on your distro.  You can just uninstall and install the older
>> version if your package managed doesn't support downgrading.  But try to
>> keep on the newer one and fix your workflow.
>>
>>
>>> br aki
>>>
>>
>> _______________________________________________
>>> libvirt-users mailing list
>>> libvirt-users at redhat.com
>>> https://www.redhat.com/mailman/listinfo/libvirt-users
>>>
>>
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