[PATCH 4/4] x86/CPU/AMD: Calculate LLC ID from number of sharing threads

[Suravee Suthikulpanit]

Last-Level-Cache ID can be calculated from the number of threads sharing
the cache, which is available from CPUID Fn0x8000001D (Cache Properties).
This is used to left-shift the APIC ID to derive LLC ID.

Therefore, default to this method unless the APIC ID enumeration does not
follow the scheme.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
---
 arch/x86/include/asm/cacheinfo.h |  7 +++++++
 arch/x86/kernel/cpu/amd.c        | 19 +++----------------
 arch/x86/kernel/cpu/cacheinfo.c  | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 47 insertions(+), 16 deletions(-)
 create mode 100644 arch/x86/include/asm/cacheinfo.h

diff --git a/arch/x86/include/asm/cacheinfo.h b/arch/x86/include/asm/cacheinfo.h
new file mode 100644
index 0000000..e958e28
--- /dev/null
+++ b/arch/x86/include/asm/cacheinfo.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_CACHEINFO_H
+#define _ASM_X86_CACHEINFO_H
+
+void cacheinfo_amd_init_llc_id(struct cpuinfo_x86 *c, int cpu, u8 node_id);
+
+#endif /* _ASM_X86_CACHEINFO_H */
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 922f43c..2c1a9f2 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -9,6 +9,7 @@
 #include <linux/random.h>
 #include <asm/processor.h>
 #include <asm/apic.h>
+#include <asm/cacheinfo.h>
 #include <asm/cpu.h>
 #include <asm/smp.h>
 #include <asm/pci-direct.h>
@@ -343,22 +344,8 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
 				c->x86_max_cores /= smp_num_siblings;
 		}
 
-		/*
-		 * We may have multiple LLCs if L3 caches exist, so check if we
-		 * have an L3 cache by looking at the L3 cache CPUID leaf.
-		 */
-		if (cpuid_edx(0x80000006)) {
-			if (c->x86 == 0x17) {
-				/*
-				 * LLC is at the core complex level.
-				 * Core complex id is ApicId[3].
-				 */
-				per_cpu(cpu_llc_id, cpu) = c->apicid >> 3;
-			} else {
-				/* LLC is at the node level. */
-				per_cpu(cpu_llc_id, cpu) = node_id;
-			}
-		}
+		cacheinfo_amd_init_llc_id(c, cpu, node_id);
+
 	} else if (cpu_has(c, X86_FEATURE_NODEID_MSR)) {
 		u64 value;
 
diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index 54d04d5..67f4790 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -637,6 +637,43 @@ static int find_num_cache_leaves(struct cpuinfo_x86 *c)
 	return i;
 }
 
+void cacheinfo_amd_init_llc_id(struct cpuinfo_x86 *c, int cpu, u8 node_id)
+{
+	/*
+	 * We may have multiple LLCs if L3 caches exist, so check if we
+	 * have an L3 cache by looking at the L3 cache CPUID leaf.
+	 */
+	if (!cpuid_edx(0x80000006))
+		return;
+
+	if (c->x86 < 0x17) {
+		/* LLC is at the node level. */
+		per_cpu(cpu_llc_id, cpu) = node_id;
+	} else if (c->x86 == 0x17 &&
+		   c->x86_model >= 0 && c->x86_model <= 0x1F) {
+		/*
+		 * LLC is at the core complex level.
+		 * Core complex id is ApicId[3] for these processors.
+		 */
+		per_cpu(cpu_llc_id, cpu) = c->apicid >> 3;
+	} else {
+		/* LLC ID is calculated from the number of thread sharing. */
+		u32 eax, ebx, ecx, edx, num_sharing_cache = 0;
+		u32 llc_index = find_num_cache_leaves(c) - 1;
+
+		cpuid_count(0x8000001d, llc_index, &eax, &ebx, &ecx, &edx);
+		if (eax)
+			num_sharing_cache = ((eax >> 14) & 0xfff) + 1;
+
+		if (num_sharing_cache) {
+			int bits = get_count_order(num_sharing_cache) - 1;
+
+			per_cpu(cpu_llc_id, cpu) = c->apicid >> bits;
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(cacheinfo_amd_init_llc_id);
+
 void init_amd_cacheinfo(struct cpuinfo_x86 *c)
 {
 
-- 
2.7.4