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26 February 2021

Patching the kernel on Fedora

by Arjen P. de Vries

My desktop has run Fedora Core ever since I joined CWI in 1999 (and I remember being excited that a real institute ran all its desktops on Linux!).

Things usually run perfectly fine, aside the occasional struggle with SELinux, GNOME and Wayland to make those do what I want. Not that long after my update to Fedora Core 33 (FC33), but not right away, the graphical drivers started to misbehave. Luckily, I was not the first to encounter this problem, and after a few searches I discovered that the Red Hat team had already been working toward a solution for [Bug 1925346] (Screen glitches after updating to Kernel 5.10.10).

Red Hat’s Hans de Goede has created koji kernels as a workaround, that seem to resolve the problem, but these do not go well together with UEFI BIOSes (those are unsigned). Kindly, Hans has shared a patch, so off we go! Back to the times predating Red Hat and Ubuntu, when we had to build our own kernels on a regular basis…

Note: You do not have to compile a kernel any longer, since the proposed update is already available in the Red Hat testing repo.


Fedora Core has a handy kernel build system that is however not that well documented (although there is some info on the wiki).

Depending on the size of the partition that contains your home directory, it may be wise to select a location on a different disk for the intermediate files that are created during the building process:


Move the package repository to this new location:

mkdir -p ${MYRPMROOT}

echo %_topdir ${MYRPMROOT} >> ${HOME}/.rpmmacros

Clone the kernel tree and switch to the FC33 release branch:

fedpkg clone -a kernel
cd kernel
fedpkg switch-branch f33


In kernel.spec set buildid to .i915p (or whatever you like); and set the signing certificate (creating your own kernel siging certificates is a nice topic for a companion post…).

%define buildid .i915p
%define pe_signing_cert {Tiqre BV}

Configure the kernel (modules) by modifying the kernel-local file, that will be picked up when you build; see also the kconfig.txt documentation.

cat >> kernel-local <<__EOF__

The options I chose here ensure that the kernel config file ends up in /proc/config.gz. An alternative approach would be to directly copy (and then edit) an existing kernel config file to .config:

cp kernel-x86_64-fedora.config .config

Add patches

Download the patch file provided and copy it into the kernel directory:

cp ~/Downloads/i915-fixes.patch .

Add the patch name to kernel.spec, at the bottom of the list of patches that should be applied (right above # END OF PATCH DEFINITIONS):

Patch9001: i915-fixes.patch

When building the kernel below, the logs include the results of applying the three individual patches to the Intel drivers that make up the i915-fixes patch:

Applying: drm/i915/gt: One more flush for Baytrail clear residuals
Applying: drm/i915/gt: Flush before changing register state
Applying: drm/i915/gt: Correct surface base address for renderclear

Build the kernel

Install kernel-specific dependencies and build a new kernel (assuming that you do not need the debug versions of kernel and modules):

sudo dnf builddep kernel.spec
make release

I think you can safely ignore the error: %changelog not in descending chronological order (seems to be a known problem with timezones in the rpm version that ships with FC33).

You can now build a complete kernel release with fedpkg local but I prefer the fast track approach that creates less packages, by for example not including the debug ones in the build:

fedpkg srpm
export MYKERNELVERSION=kernel-5.10.17-206.i915p
./scripts/ x86_64 ${MYKERNELVERSION}.fc33.src.rpm

Adapt the kernel version environment variable according to output!

Now, go make yourself a large cup of coffee, because no matter how powerful machines have become, building a kernel takes considerable time.

Install the kernel

Upon successful completion of the build, the new packages are created in the RPMS directory we created at the start. Install the files using dnf:

sudo dnf install $MYRPMROOT/RPMS/x86_64/*${MYKERNELVERSION}*

After rebooting, uname -sr shows the (expected) Linux 5.10.17-206.i915p.fc33.x86_64, and, no more problems with the Intel video card.


Hans de Goede has been so kind to share the composite patch that contains the exact three modifications on the Intel driver that we need. Also, I would never have understood the Fedora kernel compilation process without this very helpful post.

tags: linux