linux-kernel - Re: [PATCH v1 02/26] x86/cpu: Sanitize CPUID(0x80000000) output

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Message-ID: <6b0c87e0-d98d-4394-85bd-8abf556ebf0f@citrix.com>
Date: Wed, 7 May 2025 09:50:48 +0100
From: Andrew Cooper <andrew.cooper3@...rix.com>
To: "Ahmed S. Darwish" <darwi@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>,
 John Ogness <john.ogness@...utronix.de>, x86@...nel.org,
 x86-cpuid@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 02/26] x86/cpu: Sanitize CPUID(0x80000000) output

On 06/05/2025 6:04 am, Ahmed S. Darwish wrote:
> CPUID(0x80000000).EAX returns the max extended CPUID leaf available.  On
> x86-32 machines

How certain are you that it's all 32bit CPUs?  AIUI, it's an Intel
specific behaviour, not shared by other x86 vendors of the same era.

~Andrew