linux-kernel - Re: [PATCH v3 21/21] x86/fpu/xstate: Introduce boot-parameters to control some state component support

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Date:   Wed, 23 Dec 2020 10:37:52 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     "Chang S. Bae" <chang.seok.bae@...el.com>, bp@...e.de,
        luto@...nel.org, tglx@...utronix.de, mingo@...nel.org,
        x86@...nel.org
Cc:     len.brown@...el.com, dave.hansen@...el.com, jing2.liu@...el.com,
        ravi.v.shankar@...el.com, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 21/21] x86/fpu/xstate: Introduce boot-parameters to
 control some state component support

On 12/23/20 7:57 AM, Chang S. Bae wrote:
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 44fde25bb221..a67ae04d43c5 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -6002,6 +6002,21 @@
>  			which allow the hypervisor to 'idle' the guest on lock
>  			contention.
>  
> +	xstate.enable=	[X86-64]
> +	xstate.disable=	[X86-64]
> +			The kernel is compiled with a default xstate bitmask --
> +			enabling it to use the XSAVE hardware to efficiently
> +			save and restore thread states on context switch.
> +			xstate.enable allows adding to that default mask at
> +			boot-time without recompiling the kernel just to support
> +			the new thread state. (Note that the kernel will ignore
> +			any bits in the mask that do not correspond to features
> +			that are actually available in CPUID)  xstate.disable

			                               CPUID.)

> +			allows clearing bits in the default mask, forcing the
> +			kernel to forget that it supports the specified thread
> +			state. When a bit set for both, the kernel takes
> +			xstate.disable in a priority.

			               as a priority.
?


thanks.
-- 
~Randy