[ubuntu-studio-devel] Disabling KPTI

[Ralf Mardorf]

Has anybody already compared the DSP load/audio real-time performance,
when booting linux-lowlatency with and without the "nopti" option?

[root at archlinux rocketmouse]# systemd-nspawn -qD /mnt/moonstudio lsb_release -a
LSB Version:	core-9.20160110ubuntu0.2-amd64:core-9.20160110ubuntu0.2-noarch:security-9.20160110ubuntu0.2-amd64:security-9.20160110ubuntu0.2-noarch
Distributor ID:	Ubuntu
Description:	Ubuntu 16.04.4 LTS
Release:	16.04
Codename:	xenial
[root at archlinux rocketmouse]# systemd-nspawn -qD /mnt/moonstudio apt list -a linux-lowlatency
Listing... Done
linux-lowlatency/xenial-updates,xenial-security,now 4.4.0.116.122 amd64 [installed]
linux-lowlatency/xenial 4.4.0.21.22 amd64

I already booted my Ubuntu install with and without "nopti", but had no
time to test performance.

Depending on booting with or without "nopti" the command
"cat /sys/devices/system/cpu/vulnerabilities/meltdown" either shows
"Mitigation: PTI" or "Vulnerable".