arm64: Add override for ID_AA64MMFR4_EL1.NV_frac

Browse source

In a very unsurprising turn of events, there is a large class of
firmware that is totally unable to deal with FEAT_NV3, and doesn't
set the required SCR2_EL3.NV3En bit, leading to an UNDEF exception
or an unhandled trap to EL3, depending on the implementation.

Allow the unfortunate user to override ID_AA64MMFR4_EL1.NV_frac
and get a working system. Hopefully firmware will be fixed before
actually HW ships, but I have been there before... :-/

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://patch.msgid.link/20260730071022.296811-30-maz@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>

...

This commit is contained in:

Marc Zyngier 2026-07-30 08:10:22 +01:00 • committed by Oliver Upton

parent 1f4a10ff90

commit 13c164acef

4 changed files with 15 additions and 1 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

1

arch/arm64/include/asm/cpufeature.h

View file

4

arch/arm64/kernel/cpufeature.c

View file

1

arch/arm64/kernel/image-vars.h

View file

10

arch/arm64/kernel/pi/idreg-override.c

View file