linux-kernel - Re: [PATCH v3 05/21] x86/fpu/xstate: Add a new variable to indicate dynamic user states

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Date:   Fri, 15 Jan 2021 14:39:24 +0100
From:   Borislav Petkov <bp@...e.de>
To:     "Chang S. Bae" <chang.seok.bae@...el.com>
Cc:     luto@...nel.org, tglx@...utronix.de, mingo@...nel.org,
        x86@...nel.org, len.brown@...el.com, dave.hansen@...el.com,
        jing2.liu@...el.com, ravi.v.shankar@...el.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 05/21] x86/fpu/xstate: Add a new variable to indicate
 dynamic user states

On Wed, Dec 23, 2020 at 07:57:01AM -0800, Chang S. Bae wrote:
> The perf has a buffer that is allocated on demand. The states saved in the

What's "the perf"? I hope to find out when I countinue reading...

> buffer were named as 'dynamic' (supervisor) states but the buffer is not
> updated in every context switch.
> 
> The context switch buffer is in preparation to be dynamic for user states.
> Make the wording to differentiate between those 'dynamic' states.
> 
> Add a new variable -- xfeatures_mask_user_dynamic to indicate the dynamic
> user states, and rename some define and helper as related to the dynamic
> supervisor states:
> 	xfeatures_mask_supervisor_dynamic()
> 	XFEATURE_MASK_SUPERVISOR_DYNAMIC
> 
> No functional change.

Text needs cleaning up.

> Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
> Reviewed-by: Len Brown <len.brown@...el.com>
> Cc: x86@...nel.org
> Cc: linux-kernel@...r.kernel.org
> ---
> Changes from v2:
> * Updated the changelog for clarification.
> ---
>  arch/x86/include/asm/fpu/xstate.h | 12 +++++++-----
>  arch/x86/kernel/fpu/xstate.c      | 29 +++++++++++++++++++----------
>  2 files changed, 26 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
> index 24bf8d3f559a..6ce8350672c2 100644
> --- a/arch/x86/include/asm/fpu/xstate.h
> +++ b/arch/x86/include/asm/fpu/xstate.h
> @@ -56,7 +56,7 @@
>   * - Don't set the bit corresponding to the dynamic supervisor feature in
>   *   IA32_XSS at run time, since it has been set at boot time.
>   */
> -#define XFEATURE_MASK_DYNAMIC (XFEATURE_MASK_LBR)
> +#define XFEATURE_MASK_SUPERVISOR_DYNAMIC (XFEATURE_MASK_LBR)

Is XFEATURE_MASK_USER_DYNAMIC coming too?

-- 
Regards/Gruss,
    Boris.

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