linux-kernel - [PATCH v2 2/2] x86/AMD: Group cpu_llc_id assignment by topology feature and family

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Date:   Fri, 28 Oct 2016 10:51:58 -0500
From:   Yazen Ghannam <Yazen.Ghannam@....com>
To:     <linux-kernel@...r.kernel.org>
CC:     <x86@...nel.org>, <bp@...e.de>,
        Yazen Ghannam <Yazen.Ghannam@....com>
Subject: [PATCH v2 2/2] x86/AMD: Group cpu_llc_id assignment by topology feature and family

Currently, we assume that a system has multiple last level caches only if
there are multiple nodes, and that the cpu_llc_id is equal to the node_id.
This no longer applies since Fam17h can have multiple last level caches
within a node.

So group the cpu_llc_id assignment by topology feature and family.

The NODEID_MSR feature only applies to Fam10h in which case the llc is at
the node level.

The TOPOEXT feature is used on families 15h, 16h and 17h. So far we only
see multiple last level caches if L3 caches are available. Otherwise, the
cpu_llc_id will default to be the phys_proc_id. We have L3 caches only on
families 15h and 17h. On Fam15h, the llc is at the node level. On Fam17h,
the llc is at the core complex level and can be found by right shifting the
apicid. Also, keep the family checks explicit so that new families will
fall back to the default.

Single node systems in families 10h and 15h will have a Node ID of 0 which
will be the same as the phys_proc_id, so we don't need to check for
multiple nodes before using the node_id.

Signed-off-by: Yazen Ghannam <Yazen.Ghannam@....com>
---
 arch/x86/kernel/cpu/amd.c | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index c3fc337..be70345 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -314,11 +314,31 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
 		smp_num_siblings = ((ebx >> 8) & 3) + 1;
 		c->x86_max_cores /= smp_num_siblings;
 		c->cpu_core_id = ebx & 0xff;
+
+		/*
+		 * 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 == 0x15) {
+				/* LLC is at the node level. */
+				per_cpu(cpu_llc_id, cpu) = node_id;
+
+			} else 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 if (cpu_has(c, X86_FEATURE_NODEID_MSR)) {
 		u64 value;

 		rdmsrl(MSR_FAM10H_NODE_ID, value);
 		node_id = value & 7;
+
+		per_cpu(cpu_llc_id, cpu) = node_id;
 	} else
 		return;

@@ -329,9 +349,6 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
 		set_cpu_cap(c, X86_FEATURE_AMD_DCM);
 		cus_per_node = c->x86_max_cores / nodes_per_socket;

-		/* store NodeID, use llc_shared_map to store sibling info */
-		per_cpu(cpu_llc_id, cpu) = node_id;
-
 		/* core id has to be in the [0 .. cores_per_node - 1] range */
 		c->cpu_core_id %= cus_per_node;
 	}
@@ -356,15 +373,6 @@ static void amd_detect_cmp(struct cpuinfo_x86 *c)
 	/* use socket ID also for last level cache */
 	per_cpu(cpu_llc_id, cpu) = c->phys_proc_id;
 	amd_get_topology(c);
-
-	/*
-	 * Fix percpu cpu_llc_id here as LLC topology is different
-	 * for Fam17h systems.
-	 */
-	 if (c->x86 != 0x17 || !cpuid_edx(0x80000006))
-		return;
-
-	per_cpu(cpu_llc_id, cpu) = c->apicid >> 3;
 #endif
 }

-- 
1.9.1