kernel-hwcap.h change causing full kernel rebuilds

[Joey Gouly]

Hi!

On Tue, Apr 21, 2026 at 06:52:55AM -0600, Jens Axboe wrote:
> Hi,
> 
> Maybe this has already been reported, but a quick search on lore did
> not find anything. So here goes... After commit:

Here you go!

https://lore.kernel.org/linux-arm-kernel/20260413-arm64-hwcap-gen-fix-v1-1-26c56aed6908@kernel.org/

and on it's in rc1 now:

https://lore.kernel.org/linux-arm-kernel/aeaDFH0-2zhOQTxy@arm.com/


Thanks,
Joey

> 
> commit abed23c3c44f565dc812563ac015be70dd61e97b
> Author: Mark Brown <broonie at kernel.org>
> Date:   Mon Mar 2 22:53:16 2026 +0000
> 
>     arm64/hwcap: Generate the KERNEL_HWCAP_ definitions for the hwcaps
> 
> arch/arm64/include/generated/asm/kernel-hwcap.h is generated for
> _every build_, which means that you can literally run make back to back
> without _any_ source changes and you are rewarded with a full kernel
> rebuild. Not sure how this ever got past any kind of testing, because
> it's very noticeable.
> 
> For now I've reverted this change locally as any kind of testing now
> kicks off a full build, when a single file rebuild is all that is
> needed.
> 
> -- 
> Jens Axboe
> 
> 
>