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 22:42:44 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: "Luck, Tony" <tony.luck@...el.com>, "H. Peter Anvin" <hpa@...or.com>,
 Borislav Petkov <bp@...en8.de>
Cc: 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

On Fri, May 17 2024 at 18:17, Luck, Tony wrote:
>> 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.

As all initializers are macro based, that's really a non-problem.

Thanks,

        tglx