Patching gentoo-sources with RT patch

[audiodef]

I went looking for info about patching gentoo-sources with the RT patch, and found exactly what I was looking for. I prefer a step-by-step guide, so I wrote one of my own. Hope it's useful.

(Why? Well, it made sense to me to want a kernel patched with Gentoo patches and the RT patch. Why does it have to be either a Gentoo-patched kernel or a vanilla kernel patched with RT? Turns out it was a pretty simple thing to do.)

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Exact versions must match. Check https://cdn.kernel.org/pub/linux/kernel/projects/rt/ and compare with eix gentoo-sources.
Example: As of 20 Feb 2024, there is both gentoo-sources-6.6.15 and patch-6.6.15-rt22.patch.xz.

Notes:
* Make sure your portage is up-to-date and your system has been depcleaned.
* rm -rf unused kernel dirs in /usr/src - but double check that they are unused (unmerged or depcleaned).
* rm .old stuff in /boot if not needed.

1. First, make sure the unpatched kernel works on your computer. While it most likely will work with genkernel, this is not a 100% safe assumption. As a general reminder of procedures:

a. Emerge the sources
b. eselect the version
c. make sure /boot is mounted
d. genkernel all
e. grub-mkconfig
f. reboot. If it fails to find your root device, you either need to find which driver was not compiled in by default, and/or check to make sure nvme is compiled in, not compiled as module(s).

2. emerge =gentoo-sources-6.6.15 (no use flags enabled)

3. eselect kernel list

4. eselect kernel set (number corresponding to linux-6.6.15-gentoo)

5. cd /usr/src/linux

6. cp .config .config-working (or whatever identifier you prefer)

7. wget https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.6/patch-6.6.15-rt22.patch.xz

8. xzcat patch-6.6.15-rt22.patch.xz | patch -p1

9. genkernel --menuconfig all

10. Select General setup ---> Configure standard kernel features (expert users)

11. Select General setup ---> Preemption Model (Fully Preemptible Kernel (Real Time))

12. Deselect Mitigations for speculative execution vulnerabilities

13. Select Power management and ACPI options ---> CPU Frequency scaling ---> Default CPUFreq governor (performance)

14. Any other kernel config options you need, if you know you need them.

15. Exit out of menuconfig, chose Yes to save config, and let genkernel work. This will create new kernel images with "rt" in the filenames, so no need to worry about overwriting your working existing images.

16. grub-mkconfig -o /boot/grub/grub.cfg

17. Reboot

18. Test by running Cadence or similar software that identifies your system's RT status.
_________________
decibel Linux: https://decibellinux.org
Github: https://github.com/Gentoo-Music-and-Audio-Technology
Facebook: https://www.facebook.com/decibellinux
Discord: https://discord.gg/73XV24dNPN

[grknight]

[Suicidal]

[audiodef]

[CaptainBlood]

[CaptainBlood]

Using patch-xxxxx here too instead of patches-xxxxx.
I've never understood how to work with patches-xxxxx, which failed when applied in a straight forward way.

Thks 4 ur attention, interest & support.
_________________
USE="-* ..." in /etc/portage/make.conf here.
LT: "I've been doing a passable imitation of the Fontana di Trevi, except my medium is mucus. Sooo much mucus. "

[audiodef]

I tried patches myself, and I suspect all of the patches need to be directly in /etc/portage/patches/sys-kernel/gentoo-sources-x.y.z/ instead of in a subdir called "patches", which is what you get when you unpack the patches archive.
_________________
decibel Linux: https://decibellinux.org
Github: https://github.com/Gentoo-Music-and-Audio-Technology
Facebook: https://www.facebook.com/decibellinux
Discord: https://discord.gg/73XV24dNPN

[CaptainBlood]

Do you have any idea of an advantage of patches-xxxx over patch-xxxx, as patches is much bigger, iirc?

Thks 4 ur attention, interest & support.
_________________
USE="-* ..." in /etc/portage/make.conf here.
LT: "I've been doing a passable imitation of the Fontana di Trevi, except my medium is mucus. Sooo much mucus. "

[szatox]

Bonus point, if you omit version number in the directory name, emerge will attempt to apply those patches to all versions of the package (gentoo-sources in this case).
Obviously, this may or may not result in conflicts, but it is a nice feature when it works.
_________________
Make Computing Fun Again

[CaptainBlood]

[CaptainBlood]