linux-kernel - RE: [PATCH v2] x86/cpu: Fix x86_match_cpu() to match just X86_VENDOR

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Date: Fri, 17 May 2024 18:17:26 +0000
From: "Luck, Tony" <tony.luck@...el.com>
To: "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>
CC: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	"Dave Hansen" <dave.hansen@...ux.intel.com>, "x86@...nel.org"
	<x86@...nel.org>, "Peter Zijlstra (Intel)" <peterz@...radead.org>, Uros
 Bizjak <ubizjak@...il.com>, "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
	"Arnd Bergmann" <arnd@...db.de>, Mateusz Guzik <mjguzik@...il.com>, "Thomas
 Renninger" <trenn@...e.de>, Greg Kroah-Hartman <gregkh@...e.de>, Andi Kleen
	<ak@...ux.intel.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "patches@...ts.linux.dev"
	<patches@...ts.linux.dev>
Subject: RE: [PATCH v2] x86/cpu: Fix x86_match_cpu() to match just
 X86_VENDOR_INTEL

> I'm confused. Why not simply use say -1 for wildcard vendor match, -2 for no vendor ID (no CPUID or other known probing mechanism) and -3 for unrecognized vendor (vendor detectable but not known.)

It was really convenient to have "0" be the wildcard for all of vendor, family, model, stepping, feature because users of x86_match_cpu() could just initialize the fields they cared about in the struct x86_cpu_id and have the compiler make the rest be 0 automagically.

But X86_VENDOR_INTEL being zero has always been a thorn in that scheme.

-Tony