linux-kernel - [tip: x86/cpu] x86/cacheinfo: Refactor CPUID leaf 0x2 cache descriptor lookup

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Message-ID: <174289539477.14745.16854264159972359321.tip-bot2@tip-bot2>
Date: Tue, 25 Mar 2025 09:36:34 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
 "Ahmed S. Darwish" <darwi@...utronix.de>, Ingo Molnar <mingo@...nel.org>,
 "H. Peter Anvin" <hpa@...or.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject:
 [tip: x86/cpu] x86/cacheinfo: Refactor CPUID leaf 0x2 cache descriptor lookup

The following commit has been merged into the x86/cpu branch of tip:

Commit-ID:     ee159792a4db06e359a5e2e231c6f1242ec76c31
Gitweb:        https://git.kernel.org/tip/ee159792a4db06e359a5e2e231c6f1242ec76c31
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Mon, 24 Mar 2025 14:33:00 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 25 Mar 2025 10:22:13 +01:00

x86/cacheinfo: Refactor CPUID leaf 0x2 cache descriptor lookup

Extract the cache descriptor lookup logic out of the leaf 0x2 parsing
code and into a dedicated function.  This disentangles such lookup from
the deeply nested leaf 0x2 parsing loop.

Remove the cache table termination entry, as it is no longer needed
after the ARRAY_SIZE()-based lookup.

[ darwi: Move refactoring logic into this separate commit + commit log.
	 Remove the cache table termination entry. ]

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ahmed S. Darwish <darwi@...utronix.de>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Link: https://lore.kernel.org/r/20250324133324.23458-6-darwi@linutronix.de
---
 arch/x86/kernel/cpu/cacheinfo.c | 44 ++++++++++++++------------------
 1 file changed, 20 insertions(+), 24 deletions(-)

diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index 6c61080..d0bfdb8 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -123,7 +123,6 @@ static const struct _cache_table cache_table[] =
 	{ 0xea, LVL_3,      MB(12) },	/* 24-way set assoc, 64 byte line size */
 	{ 0xeb, LVL_3,      MB(18) },	/* 24-way set assoc, 64 byte line size */
 	{ 0xec, LVL_3,      MB(24) },	/* 24-way set assoc, 64 byte line size */
-	{ 0x00, 0, 0}
 };
 
 
@@ -728,6 +727,16 @@ void init_hygon_cacheinfo(struct cpuinfo_x86 *c)
 	ci->num_leaves = find_num_cache_leaves(c);
 }
 
+static const struct _cache_table *cache_table_get(u8 desc)
+{
+	for (int i = 0; i < ARRAY_SIZE(cache_table); i++) {
+		if (cache_table[i].descriptor == desc)
+			return &cache_table[i];
+	}
+
+	return NULL;
+}
+
 void init_intel_cacheinfo(struct cpuinfo_x86 *c)
 {
 	/* Cache sizes */
@@ -784,34 +793,21 @@ void init_intel_cacheinfo(struct cpuinfo_x86 *c)
 
 	/* Don't use CPUID(2) if CPUID(4) is supported. */
 	if (!ci->num_leaves && c->cpuid_level > 1) {
+		const struct _cache_table *entry;
 		union leaf_0x2_regs regs;
 		u8 *desc;
 
 		cpuid_get_leaf_0x2_regs(&regs);
 		for_each_leaf_0x2_desc(regs, desc) {
-			u8 k = 0;
-
-			/* look up this descriptor in the table */
-			while (cache_table[k].descriptor != 0) {
-				if (cache_table[k].descriptor == *desc) {
-					switch (cache_table[k].cache_type) {
-					case LVL_1_INST:
-						l1i += cache_table[k].size;
-						break;
-					case LVL_1_DATA:
-						l1d += cache_table[k].size;
-						break;
-					case LVL_2:
-						l2 += cache_table[k].size;
-						break;
-					case LVL_3:
-						l3 += cache_table[k].size;
-						break;
-					}
-
-					break;
-				}
-				k++;
+			entry = cache_table_get(*desc);
+			if (!entry)
+				continue;
+
+			switch (entry->cache_type) {
+			case LVL_1_INST: l1i += entry->size; break;
+			case LVL_1_DATA: l1d += entry->size; break;
+			case LVL_2:	 l2  += entry->size; break;
+			case LVL_3:	 l3  += entry->size; break;
 			}
 		}
 	}