linux-kernel - Re: [PATCH v5 00/35] x86: Introduce a centralized CPUID data model

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Message-ID: <aLrdImDdg5utz2ZF@lx-t490>
Date: Fri, 5 Sep 2025 14:52:50 +0200
From: "Ahmed S. Darwish" <darwi@...utronix.de>
To: Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Sean Christopherson <seanjc@...gle.com>,
	David Woodhouse <dwmw2@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Sohil Mehta <sohil.mehta@...el.com>,
	John Ogness <john.ogness@...utronix.de>, x86@...nel.org,
	x86-cpuid@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 00/35] x86: Introduce a centralized CPUID data model

Hi,

On Fri, 05 Sep 2025, Ahmed S. Darwish wrote:
>
>     /*
>      * Compile-time failure: Requested subleaf > max dynamic subleaf
>      * CPUID(0xd).n, n > 62
>      */
>
>     cpuid_subleaf_n(&boot_cpu_data, 0xd, 63);
>

Sorry, this actually is:

    /*
     * Compile-time failure: Requested subleaf > max dynamic subleaf
     * CPUID(0xd).n, n > 63
     */

    cpuid_subleaf_n(&boot_cpu_data, 0xd, 64);

which is the correct thing, as per the Intel SDM manuals: n <= 63.

That false upper-bound snippet was a left over from a previous cover
letter draft.  That is, before the x86-cpuid-db commit:

    https://gitlab.com/x86-cpuid.org/x86-cpuid-db/-/commit/f3d9bc48b4a

Thanks!

--
Ahmed S. Darwish
Linutronix GmbH