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

root@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=true,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 .

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 .

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 .