linux-kernel - [PATCH v1 1/2] x86/cacheinfo: Properly parse CPUID(0x80000005) L1d/L1i associativity

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250409105429.1048199-2-darwi@linutronix.de>
Date: Wed,  9 Apr 2025 12:54:24 +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 v1 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 b3a520959b51..7a95e1ce73f8 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -208,6 +208,9 @@ union l3_cache {
 	unsigned val;
 };
 
+#define AMD_CPUID4_FULLY_ASSOCIATIVE	0xffff
+
+/* L2/L3 associativity mapping */
 static const unsigned short assocs[] = {
 	[1] = 1,
 	[2] = 2,
@@ -219,7 +222,7 @@ static const unsigned short assocs[] = {
 	[0xc] = 64,
 	[0xd] = 96,
 	[0xe] = 128,
-	[0xf] = 0xffff /* fully associative - no way to show this currently */
+	[0xf] = AMD_CPUID4_FULLY_ASSOCIATIVE
 };
 
 static const unsigned char levels[] = { 1, 1, 2, 3 };
@@ -258,7 +261,7 @@ amd_cpuid4(int leaf, union _cpuid4_leaf_eax *eax,
 	case 0:
 		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;
@@ -295,7 +298,7 @@ amd_cpuid4(int leaf, union _cpuid4_leaf_eax *eax,
 	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;
 	ebx->split.ways_of_associativity = assoc - 1;
-- 
2.49.0