linux-kernel - Re: [PATCH v1 10/12] tools/x86/kcpuid: Update bitfields to x86-cpuid-db v2.0

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Message-ID: <Z8sLmGf2L4mszUEp@lx-t490>
Date: Fri, 7 Mar 2025 16:07:04 +0100
From: "Ahmed S. Darwish" <darwi@...utronix.de>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Cooper <andrew.cooper3@...rix.com>, x86@...nel.org,
	John Ogness <john.ogness@...utronix.de>, x86-cpuid@...ts.linux.dev,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 10/12] tools/x86/kcpuid: Update bitfields to
 x86-cpuid-db v2.0

On Thu, 06 Mar 2025, H. Peter Anvin wrote:
>
> Leaf 3h was not unique to Transmeta.
>

Thanks, I missed that Pentium III can provide leaf 0x3 as well.

It seems that leaf 0x3's format differs between Intel and Transmeta.  On
Intel, PSN is at ECX:EDX, while on Transmeta, the PSN is at EAX:EBX, and
ECX:EDX on non-evaluation models provide the rest. [*]

Unfortunately, so far, x86-cpuid-db does not support having a CPUID
bitfield with different interpretations across vendors.

Given that Linux force disables PSN at early boot, I'll just remove that
leaf from the database — for now.  (Time wise, finishing the new
linux/arch/x86/ CPUID data model for mainline submission is a much higher
priority.)

All the best,
Ahmed

[*] "Processor Recognition", Transmeta Corporation, 2002/05/07.