linux-kernel - Re: [PATCH 23/23] x86/fpu: Defer FPU state load until return to userspace

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Date:   Thu, 8 Nov 2018 09:33:04 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, Andy Lutomirski <luto@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>,
        Rik van Riel <riel@...riel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH 23/23] x86/fpu: Defer FPU state load until return to
 userspace

On 2018-11-07 20:48:58 [+0100], To linux-kernel@...r.kernel.org wrote:
> index 8c03b42416656..d10b60d80d35a 100644
> --- a/arch/x86/include/asm/fpu/api.h
> +++ b/arch/x86/include/asm/fpu/api.h

The bot complained about missing definition for local_bh_disable() so I
swapped the preempt.h for bottom_half.h at the beginning of this file.

> @@ -27,17 +27,31 @@ extern void __kernel_fpu_end(void);
>  extern void kernel_fpu_begin(void);
>  extern void kernel_fpu_end(void);
>  extern bool irq_fpu_usable(void);
> +extern void fpregs_mark_activate(void);
>  
>  static inline void __fpregs_changes_begin(void)
>  {
>  	preempt_disable();
> +	local_bh_disable();
>  }
>  
>  static inline void __fpregs_changes_end(void)
>  {
> +	local_bh_enable();
>  	preempt_enable();
>  }

Sebastian