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

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Message-ID: <Z9vyJLXNL2-CTIIG@lx-t490>
Date: Thu, 20 Mar 2025 11:47:00 +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>,
	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 Wed, 19 Mar 2025, H. Peter Anvin wrote:
>
> On March 18, "Ahmed S. Darwish" wrote:
> >
> > Then I found that there are 28 other cases in the x86 tree where the
> > AMD/Hygon CPU vendor check is also combined.  So I did that macro and
> > it also made a number the affected sites more succinct; e.g.:
> >
> > ...
>
> I would agree that abstracting this into something higher level makes
> sense, but have you considered whether or not it is actually necessary
> to do this in the first place? In the case of level 0x8000001d for
> example, that should be handled by the end bracket from leaf
> 0x80000000.
>
> In general, VFMS checks are not a good thing.
>

Great point, I'll consider that when I (soon) touch these areas again.

In the next PQ, wherea cached CPUID table built on early boot, "CPUID
truth" is centralized.  This way, the VMFS checks can indeed be reduced.

Thanks!

--
Ahmed S. Darwish
Linutronix GmbH