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Subject[PATCH 4/4] x86/CPU/AMD: Calculate LLC ID from number of sharing threads
Date
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@amd.com>
---
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
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