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Re: armhf kernels on arm64 hardware

On 7/15/22 12:16, Wookey wrote:
On 2022-07-15 18:42 +0800, Paul Wise wrote:
On Fri, 2022-07-15 at 12:04 +0200, Arnd Bergmann wrote:

If you see /other/ problems with the 64-bit kernel (using the
same user space, kernel source and kernel config as the 32-bit
kernel), please report those to the respective upstream kernel
maintainers so we can fix those as well.
Gene's complaint is unrelated to this thread, but it is that Debian
refuses to support running the 32-bit ARMMP kernel on 64-bit hardware,
specifically on the RaspberryPi 4b. There wasn't any justification from
Debian given in the bug reports, but it sounds like only build config
options are needed to be enabled, but Debian refuses to do that:

Ah thanks Paul. I was wondering why we were being accused of 'Debian
abandonning armhf' when it was news to me, and I'm just writing the
'ARM ports status' talk for Debconf next week.

Clearly one normally does not run foreign-arch kernels on hardware so
we don't have to support it, and Ben is right to say 'this is not a

On the other hand, if the armhf kernel does work on RPi4 with a few
config options, and there is an actual use case, then the question is
what is the downside of enabling the config options?
It, LinuxCNC, does indeed run on an armhf kernel built right on the pi
and has been since Jessie on a rpi3b.
Does this only work for the RPi4, or does it enable/prevent 32-bit kernels on other 64-bit machines?
No. It runs with the same armhf kernel on an rpi3b, but the 3b is dragging its
tongue on the floor where the 4b has some leftover zip.

I'm driving an 80 yo Sheldon lathe with it, and a 3 axis Mazak mill is under
construction/conversion by another person out on the left coast as we're
discussing this. But the lack of armhf in Debian is why we're both running
raspian, I built his boot cards.

Because our latency-test results are better on armhf than on arm64, we use armhf
for its performance.
Do i386 kernels work on amd64 machines?
Different architecture. No relevance here.

Sounds like something that might be worth discussion at debconf next week. I'll mention it in the talk.


Cheers, Gene Heskett.
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>

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