linux-kernel - Re: [patch v5 06/19] x86/cpu: Provide a sane leaf 0xb/0x1f parser

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Date: Mon, 12 Feb 2024 16:03:41 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Borislav Petkov <bp@...en8.de>
Cc: LKML <linux-kernel@...r.kernel.org>, x86@...nel.org, Tom Lendacky
 <thomas.lendacky@....com>, Andrew Cooper <andrew.cooper3@...rix.com>,
 Arjan van de Ven <arjan@...ux.intel.com>, Huang Rui <ray.huang@....com>,
 Juergen Gross <jgross@...e.com>, Dimitri Sivanich
 <dimitri.sivanich@....com>, Sohil Mehta <sohil.mehta@...el.com>, K Prateek
 Nayak <kprateek.nayak@....com>, Kan Liang <kan.liang@...ux.intel.com>,
 Zhang Rui <rui.zhang@...el.com>, "Paul E. McKenney" <paulmck@...nel.org>,
 Feng Tang <feng.tang@...el.com>, Andy Shevchenko <andy@...radead.org>,
 Michael Kelley <mhklinux@...look.com>, "Peter Zijlstra (Intel)"
 <peterz@...radead.org>
Subject: Re: [patch v5 06/19] x86/cpu: Provide a sane leaf 0xb/0x1f parser

On Mon, Feb 12 2024 at 15:17, Thomas Gleixner wrote:
> On Tue, Jan 30 2024 at 20:31, Borislav Petkov wrote:
> TBH, the // comment style is really better for struct definitions. It's
> denser and easier to parse.
>
> 		// eax
> 		u32	x2apic_shift	:  5, // Number of bits to shift APIC ID right
> 					      // for the topology ID at the next level
> 					: 27; // Reserved
> 		// ebx
> 		u32	num_processors	: 16, // Number of processors at current level
> 					: 16; // Reserved
>
> versus:
>
> 		/* eax */
> 		u32	x2apic_shift	:  5, /*
>                                                * Number of bits to shift APIC ID right
> 					       * for the topology ID at	the next level
>                                                */
> 					: 27; /* Reserved */
>
> 		/* ebx */
> 		u32	num_processors	: 16, /* Number of processors at current level */
> 					: 16; /* Reserved */
>
> Especially x2apic_shift is horrible and the comments of EBX are visually
> impaired while with the C++ comments x2apic_shift looks natural and the
> EBX comments are just open to the right and therefore simpler.

Aside of that it would make the struct generator in the CPUID data base
more complex.