After I run a virtual machine using libvirt, the CPU performance is
significantly degraded (about 2 times). I double checked this using various
benchmarks.

This issue is only reproduced when I use 'IvyBridge-IBRS' CPU model. With
'IvyBridge' all works fine.

Performance degradation remains after VM shutdown. To reset CPU to original
performance, I need to reboot or suspend/resume my machine.

My system information:
  PROCESSOR:          Intel Core i7-3770 @ 4.10GHz (8 Cores)
  GRAPHICS:           NVIDIA GeForce GTX 660 Ti 2048MB
  MOTHERBOARD:        ASUS P8Z77-V LE PLUS
  OPERATING SYSTEM:   openSUSE 42.3 with latest updates