Re: x86 fpu: command-line parameters broken post-FPU-rewrite
From: Ingo Molnar
Date: Wed Dec 09 2015 - 03:32:17 EST
* Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
> Hey Ingo,
>
> We were starting to look at reenabling XSAVES support and tried to use the
> 'noxsave' and 'noxsaves' kernel command-line options. The rewrite moved the FPU
> initialization to before we even are parsing command-line options, even the
> early_param()s.
>
> Do you have any preferences on how it gets fixed?
>
> The most obvious thing would be to just defer as much of the FPU setup as we can
> until after parse_early_param() has happened. The only other think I can think
> of doing would be to try to do some *really* early, simple, command-line parsing
> to look for 'noxsave' and friends.
>
> Thoughts?
Hm, so given that having the FPU operational is key to a functioning kernel (and
other kernel subsystems may make use of FPU functionality), I'd rather bring
option parsing earlier than change the FPU setup sequence. FPU setup should be
done when we identify the CPU - not 'very late' as we used to.
Thanks,
Ingo
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