linux-kernel - Re: [PATCH v2] x86: Clear feature bits disabled at compile-time

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Message-ID: <20250723134640.GAaIDnwGx6cAF9FFGz@renoirsky.local>
Date: Wed, 23 Jul 2025 15:46:40 +0200
From: Borislav Petkov <bp@...en8.de>
To: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	"Kirill A. Shutemov" <kas@...nel.org>,
	Alexander Potapenko <glider@...gle.com>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Xin Li <xin3.li@...el.com>,
	Sai Praneeth <sai.praneeth.prakhya@...el.com>,
	Jethro Beekman <jethro@...tanix.com>,
	Jarkko Sakkinen <jarkko@...nel.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
	"Mike Rapoport (IBM)" <rppt@...nel.org>,
	Kees Cook <kees@...nel.org>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Yu-cheng Yu <yu-cheng.yu@...el.com>, stable@...r.kernel.org,
	Borislav Petkov <bp@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] x86: Clear feature bits disabled at compile-time

On Wed, Jul 23, 2025 at 11:22:49AM +0200, Maciej Wieczor-Retman wrote:
> +static __init void init_cpu_cap(struct cpuinfo_x86 *c)
> +{
> +	int i;
> +
> +	for (i = 0; i < NCAPINTS; i++) {
> +		cpu_caps_set[i] = REQUIRED_MASK(i);
> +		cpu_caps_cleared[i] = DISABLED_MASK(i);
> +	}
> +}

There's already apply_forced_caps(). Not another cap massaging function
please. Add that stuff there.

As to what the Fixes: tag should be - it should not have any Fixes: tag
because AFAICT, this has always been this way. So this fix should be
backported everywhere.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette