Re: [patch 17/17] x86/fpu: Move FPU initialization into arch_cpu_finalize_init()

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On 9/1/23 11:00, Nikolay Borisov wrote:

On 1.09.23 г. 20:30 ч., Guenter Roeck wrote:

On Wed, Jun 14, 2023 at 01:39:46AM +0200, Thomas Gleixner wrote:
Initializing the FPU during the early boot process is a pointless
exercise. Early boot is convoluted and fragile enough.

Nothing requires that the FPU is set up early. It has to be initialized
before fork_init() because the task_struct size depends on the FPU register
buffer size.

Move the initialization to arch_cpu_finalize_init() which is the perfect
place to do so.

No functional change.

This allows to remove quite some of the custom early command line parsing,
but that's subject to the next installment.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

The backport of this patch into chromeos-5.10 and chromeos-5.15 via stable
relase merges is causing various Chromebooks (not all of them) to crash
early during boot. Subsequent fixes have not addressed the problem for us,
so we already reverted the patch from chromeos-5.15 and will revert it
from chromeos-5.10 as well.

I don't know if this is a Chromebook specific problem, or if it affects
mainline, so this is just a heads-up in case others experience similar

Looking at 5.15 the following prerequisites are likely missing:

af8060279968 ("mm: Move mm_cachep initialization to mm_init()")
5b93a83649c7 ("x86/mm: Initialize text poking earlier")

Can you test with those patches backported to 5.15.y and see if it works?

Both patches are already in v5.10.y and 5.15.y, so unfortunately
that doesn't help.


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