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 16:43:47 +0100
From: Borislav Petkov <bp@...en8.de>
To: Thomas Gleixner <tglx@...utronix.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 04:08:31PM +0100, Thomas Gleixner wrote:
> This really makes my eyes bleed.

From: Borislav Petkov (AMD) <bp@...en8.de>
Date:   Mon Feb 12 16:41:42 2024 +0100

Documentation/maintainer-tip: Add C++ tail comments exception

Document when C++-style, tail comments should be used.

Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>

diff --git a/Documentation/process/maintainer-tip.rst b/Documentation/process/maintainer-tip.rst
index 799359231b7f..497bb39727c8 100644
--- a/Documentation/process/maintainer-tip.rst
+++ b/Documentation/process/maintainer-tip.rst
@@ -480,7 +480,7 @@ Multi-line comments::
 	 * Larger multi-line comments should be split into paragraphs.
 	 */
 
-No tail comments:
+No tail comments (see below):
 
   Please refrain from using tail comments. Tail comments disturb the
   reading flow in almost all contexts, but especially in code::
@@ -501,6 +501,34 @@ No tail comments:
 	/* This magic initialization needs a comment. Maybe not? */
 	seed = MAGIC_CONSTANT;
 
+  Use C++ style, tail comments when documenting structs in headers to
+  achieve a more compact layout and better readability::
+
+        // 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 */
+	        /*
+	         * Number of bits to shift APIC ID right for the topology ID
+	         * at the next level
+	         */
+         u32     x2apic_shift    :  5,
+		 /* Reserved */
+				 : 27;
+
+	/* ebx */
+		/* Number of processors at current level */
+	u32     num_processors  : 16,
+		/* Reserved */
+				: 16;
+
 Comment the important things:
 
   Comments should be added where the operation is not obvious. Documenting



-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette