Comment # 11 on bug 1092035 from Fei Li

Hi magist3r,
I do the same tests on a Ivy Bridge machine today. Also can not see much host
CPU performance degradation after starting one/two guest vm; and the host CPU
performance returns back after I destroy the guest vm, although not so obvious
as it is not down much after starting the vm.

My test results:
- on host without any guests started:
https://browser.geekbench.com/v4/cpu/8296205
- one opensuse42.3 vm is running: 8296600
- destroy the opensuse42.3 vm: 8296638
- two opensuse42.3 vm are running: 8296710
- destroy two opensuse42.3 vm: 8296805

One thing to note is that my data for "Single-Core Score" are all about 2000,
but I see one of your data is about 4000, that is no guests running on the
host. So one suggestion is to check whether ucode-intel/qemu/libvirt is also
the latest. :)

FYI:
The mitigation I have on both host and guest for the Ivy Bridge machine are as
below:
grep -H . /sys/devices/system/cpu/vulnerabilities/*
/sys/devices/system/cpu/vulnerabilities/meltdown:Mitigation: PTI
/sys/devices/system/cpu/vulnerabilities/spectre_v1:Mitigation: __user pointer
sanitization
/sys/devices/system/cpu/vulnerabilities/spectre_v2:Mitigation: Full generic
retpoline + IBPB