linux-kernel - Re: [PATCH 2/4] x86/fpu: introduce restore_init

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Date:	Fri, 13 Mar 2015 15:39:28 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Borislav Petkov <bp@...e.de>
Cc:	Dave Hansen <dave.hansen@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pekka Riikonen <priikone@....fi>,
	Rik van Riel <riel@...hat.com>,
	Suresh Siddha <sbsiddha@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Yu, Fenghua" <fenghua.yu@...el.com>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>
Subject: Re: [PATCH 2/4] x86/fpu: introduce restore_init_xstate()

On 03/13, Borislav Petkov wrote:
>
> > - It is not clear why we can't call setup_init_fpu_buf() unconditionally
> >   to always create init_xstate_buf().
>
> I also don't understand what the thought behind xstate_enable_boot_cpu()
> and eager_fpu_init_bp() - we do call xstate_enable_boot_cpu() and alloc
> init_xstate_buf and then when we come to
>
> eager_fpu_init
> |-> eager_fpu_init_bp
>
> we get to init it if not initted yet.
>
> When can that ever happen?

This too needs cleanups. But later ;)

Note that xstate_enable_boot_cpu is not called if !cpu_has_xsave, see the
check in xsave_init(). Howver, eagerfpu=on will force eager_fpu_init() which
calls eager_fpu_init_bp().

Btw, I was also going to kill eager_fpu_init_bp(). Probably I will send the
patch today.

> Applied, thanks.

Thanks!

Oleg.

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