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

Guenter Roeck
2023-09-01T22:55:11Z

On Fri, Sep 01, 2023 at 09:02:19PM +0300, Nikolay Borisov wrote:
>
>
> On 1.09.23 г. 20:30 ч., Guenter Roeck wrote:
> > Hi,
> >
> > 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@linutronix.de>
> >
> > 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
> > problems.
>
>
> Another thing - if you choose to revert the arch_finalize patch then bear in
> mind that the GDS' 'force' option is rendered inoperable as the FPU can't be
> disabled due to the way things are sequenced.

I understand, but that is still better than not being able to boot
in the first place.

Thanks,
Guenter