linux-kernel - [PATCH v2 1/2] x86/cacheinfo: Properly parse CPUID(0x80000005) L1d/L1i associativity

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Message-ID: <20250409122233.1058601-2-darwi@linutronix.de>
Date: Wed,  9 Apr 2025 14:22:30 +0200
From: "Ahmed S. Darwish" <darwi@...utronix.de>
To: Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>
Cc: 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>,
	"Ahmed S. Darwish" <darwi@...utronix.de>
Subject: [PATCH v2 1/2] x86/cacheinfo: Properly parse CPUID(0x80000005) L1d/L1i associativity

For the AMD CPUID(4) emulation cache info logic, the same associativity
mapping array, assocs[], is used for both CPUID(0x80000005) and
CPUID(0x80000006).

This is incorrect since per the AMD manuals, the mappings for
CPUID(0x80000005) L1d/L1i associativity is:

   n = 0x1 -> 0xfe	n
   n = 0xff		fully associative

while assocs[] maps these values to:

   n = 0x1, 0x2, 0x4	n
   n = 0x3, 0x7, 0x9	0
   n = 0x6		8
   n = 0x8		16
   n = 0xa		32
   n = 0xb		48
   n = 0xc		64
   n = 0xd		96
   n = 0xe		128
   n = 0xf		fully associative

which is only valid for CPUID(0x80000006).

Parse CPUID(0x80000005) L1d/L1i associativity values as shown in the AMD
manuals.  Since the 0xffff literal is used to denote full associativity
at the AMD CPUID(4)-emulation logic, define AMD_CPUID4_FULLY_ASSOCIATIVE
for it instead of spreading that literal in more places.

Mark the assocs[] mapping array as only valid for CPUID(0x80000006) L2/L3
cache information.

Fixes: a326e948c538 ("x86, cacheinfo: Fixup L3 cache information for AMD multi-node processors")
Cc: stable@...r.kernel.org
Signed-off-by: Ahmed S. Darwish <darwi@...utronix.de>
---
 arch/x86/kernel/cpu/cacheinfo.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index cd48d34ac04b..f4817cd50cfb 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -91,6 +91,8 @@ static const enum cache_type cache_type_map[] = {
  * AMD CPUs with TOPOEXT can just use CPUID(0x8000001d)
  */
 
+#define AMD_CPUID4_FULLY_ASSOCIATIVE	0xffff
+
 union l1_cache {
 	struct {
 		unsigned line_size	:8;
@@ -122,6 +124,7 @@ union l3_cache {
 	unsigned int val;
 };
 
+/* L2/L3 associativity mapping */
 static const unsigned short assocs[] = {
 	[1]		= 1,
 	[2]		= 2,
@@ -133,7 +136,7 @@ static const unsigned short assocs[] = {
 	[0xc]		= 64,
 	[0xd]		= 96,
 	[0xe]		= 128,
-	[0xf]		= 0xffff	/* Fully associative */
+	[0xf]		= AMD_CPUID4_FULLY_ASSOCIATIVE
 };
 
 static const unsigned char levels[] = { 1, 1, 2, 3 };
@@ -163,7 +166,7 @@ static void legacy_amd_cpuid4(int index, union _cpuid4_leaf_eax *eax,
 		if (!l1->val)
 			return;
 
-		assoc		= assocs[l1->assoc];
+		assoc		= (l1->assoc == 0xff) ? AMD_CPUID4_FULLY_ASSOCIATIVE : l1->assoc;
 		line_size	= l1->line_size;
 		lines_per_tag	= l1->lines_per_tag;
 		size_in_kb	= l1->size_in_kb;
@@ -201,7 +204,7 @@ static void legacy_amd_cpuid4(int index, union _cpuid4_leaf_eax *eax,
 	eax->split.num_threads_sharing		= 0;
 	eax->split.num_cores_on_die		= topology_num_cores_per_package();
 
-	if (assoc == 0xffff)
+	if (assoc == AMD_CPUID4_FULLY_ASSOCIATIVE)
 		eax->split.is_fully_associative = 1;
 
 	ebx->split.coherency_line_size		= line_size - 1;
-- 
2.49.0