linux-kernel - Re: [PATCH v2 01/29] x86: treewide: Introduce x86_vendor_amd_or

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Message-ID: <0f1b3c76-5430-437d-aa9f-27c1dbf9cf01@intel.com>
Date: Mon, 17 Mar 2025 11:11:11 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Peter Zijlstra <peterz@...radead.org>, Borislav Petkov <bp@...en8.de>
Cc: "Ahmed S. Darwish" <darwi@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 Thomas Gleixner <tglx@...utronix.de>,
 Andrew Cooper <andrew.cooper3@...rix.com>, "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 v2 01/29] x86: treewide: Introduce
 x86_vendor_amd_or_hygon()

On 3/17/25 10:48, Peter Zijlstra wrote:
> On Mon, Mar 17, 2025 at 06:32:16PM +0100, Borislav Petkov wrote:
>> On Mon, Mar 17, 2025 at 05:47:17PM +0100, Ahmed S. Darwish wrote:
>>> The pattern to check if an x86 vendor is AMD or HYGON (or not both) is
>>> pretty common.  Introduce x86_vendor_amd_or_hygon() at <asm/processor.h>
>> So if we need to check "intel too", we do
>>
>> x86_vendor_amd_or_hygon_or_intel?
>>
>> Nah, this is silly.
> Would it make more sense to have a Zen1 feature and check that instead?
> 
> Because, IIRC Hygon is simply a Zen1 copy.

Some of them can just go away, I think. This, for instance:

        if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
            boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
                return false;

        if (cpu_feature_enabled(X86_FEATURE_ZEN))
                return false;

Do we even need a vendor check if we're checking X86_FEATURE_ZEN? Is
someone setting X86_FEATURE_ZEN on Intel? ;)