linux-kernel - Re: [PATCH v6 05/25] x86/fpu/xstate: Remove kernel dynamic xfeatures from kernel default

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Date:   Thu, 14 Sep 2023 09:22:23 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Yang Weijiang <weijiang.yang@...el.com>, seanjc@...gle.com,
        pbonzini@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, chao.gao@...el.com,
        rick.p.edgecombe@...el.com, john.allen@....com
Subject: Re: [PATCH v6 05/25] x86/fpu/xstate: Remove kernel dynamic xfeatures
 from kernel default_features

On 9/13/23 23:33, Yang Weijiang wrote:
> --- a/arch/x86/kernel/fpu/xstate.c
> +++ b/arch/x86/kernel/fpu/xstate.c
> @@ -845,6 +845,7 @@ void __init fpu__init_system_xstate(unsigned int legacy_size)
>  	/* Clean out dynamic features from default */
>  	fpu_kernel_cfg.default_features = fpu_kernel_cfg.max_features;
>  	fpu_kernel_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC;
> +	fpu_kernel_cfg.default_features &= ~fpu_kernel_dynamic_xfeatures;

I'd much rather that this be a closer analog to XFEATURE_MASK_USER_DYNAMIC.

Please define a XFEATURE_MASK_KERNEL_DYNAMIC value and use it here.
Don't use a dynamically generated one.