linux-kernel - Re: [PATCH v4 22/22] x86/fpu/xstate: Introduce boot-parameters to control state component support

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Message-ID: <40a65a30-ce41-6a51-50f4-34a0b0b1ef6f@infradead.org>
Date:   Sun, 21 Feb 2021 12:37:46 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     "Bae, Chang Seok" <chang.seok.bae@...el.com>
Cc:     Borislav Petkov <bp@...e.de>, "luto@...nel.org" <luto@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "Brown, Len" <len.brown@...el.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Liu, Jing2" <jing2.liu@...el.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v4 22/22] x86/fpu/xstate: Introduce boot-parameters to
 control state component support

On 2/21/21 12:10 PM, Bae, Chang Seok wrote:
> On Feb 21, 2021, at 11:30, Randy Dunlap <rdunlap@...radead.org> wrote:
>> Can we tell people (in this Doc file) where to look up the values that can be
>> used in xstate.enable and xstate.disable?
> 
> Perhaps add something like this with the change below:
>     “See comment before function fpu__init_parse_early_param() in
>      arch/x86/kernel/fpu/init.c."

Hi,

I was thinking more along the lines of where can I find the value
0x60000 or BIT(22) or BIT(19), for example and see what they mean,
even though it will likely be some abbreviation.


> /*
>  * The kernel parameter "xstate.enable='mask'" and "xstate.disable='mask'" have a
>  * mask value in a subset of XFEATURE_MASK_CONFIGURABLE.
>  *
>  * The longest parameter is 22 octal number characters with '0' prefix and an extra
>  * '\0' for termination.
>  */
> #define MAX_XSTATE_MASK_CHARS   24
> 
> /**
>  * fpu__init_parse_early_param() - parse the xstate kernel parameters
>  *
>  * Parse them early because fpu__init_system() is executed before
>  * parse_early_param().
>  */
> static void __init fpu__init_parse_early_param(void)

thanks.
-- 
~Randy