linux-kernel - Re: [PATCH v4 8/8] x86/fpu/xstate: Warn if guest-only supervisor states are detected in normal fpstate

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Message-ID: <ec953e80-a39e-4d42-b75e-6f995289a669@intel.com>
Date: Tue, 1 Apr 2025 10:17:08 -0700
From: "Chang S. Bae" <chang.seok.bae@...el.com>
To: Chao Gao <chao.gao@...el.com>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>, <tglx@...utronix.de>,
	<dave.hansen@...el.com>, <seanjc@...gle.com>, <pbonzini@...hat.com>
CC: <peterz@...radead.org>, <rick.p.edgecombe@...el.com>,
	<weijiang.yang@...el.com>, <john.allen@....com>, <bp@...en8.de>,
	<xin3.li@...el.com>, Ingo Molnar <mingo@...hat.com>, Dave Hansen
	<dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, "Aruna
 Ramakrishna" <aruna.ramakrishna@...cle.com>, Mitchell Levy
	<levymitchell0@...il.com>, Adamos Ttofari <attofari@...zon.de>, Uros Bizjak
	<ubizjak@...il.com>
Subject: Re: [PATCH v4 8/8] x86/fpu/xstate: Warn if guest-only supervisor
 states are detected in normal fpstate

On 3/18/2025 8:31 AM, Chao Gao wrote:
>   
> +	WARN_ON_FPU(!fpstate->is_guest && (mask & XFEATURE_MASK_SUPERVISOR_GUEST));

Did you check xfeatures_mask_supervisor()? I think you might want to 
introduce a similar wrapper to reference the enabled features 
(max_features) here.

Also, have you audited other code paths to ensure that no additional 
guard like this is needed? Can you summarize your audit process?

Thanks,
Chang