linux-kernel - [PATCH v3 2/2] x86/amd: Fixup cpu_core_id for family17h downcore configuration

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Date:   Sun, 23 Jul 2017 23:35:23 -0500
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, bp@...e.de,
        peterz@...radead.org, Yazen.Ghannam@....com,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v3 2/2] x86/amd: Fixup cpu_core_id for family17h downcore configuration

For family17h, current cpu_core_id is directly taken from the value
CPUID_Fn8000001E_EBX[7:0] (CoreId), which is the physical ID of the
core within a die. However, on system with downcore configuration
(where not all physical cores within a die are available), this could
result in the case where cpu_core_id > (cores_per_node - 1).

Fix up the cpu_core_id by breaking down the bitfields of CoreId,
and calculate relative ID using available topology information.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 arch/x86/kernel/cpu/amd.c | 77 ++++++++++++++++++++++++++++++++++-------------
 1 file changed, 56 insertions(+), 21 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index b481df4e..62a4814 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -302,38 +302,73 @@ static int nearby_node(int apicid)
  */
 static void __get_topoext(struct cpuinfo_x86 *c)
 {
-	u8 node_id;
+	u16 l3_nshared = 0;
 	u32 eax, ebx, ecx, edx;
 	int cpu = smp_processor_id();
 
+	if (cpuid_edx(0x80000006)) {
+		cpuid_count(0x8000001d, 3, &eax, &ebx, &ecx, &edx);
+		l3_nshared = ((eax >> 14) & 0xfff) + 1;
+	}
+
 	cpuid(0x8000001e, &eax, &ebx, &ecx, &edx);
 
-	node_id = ecx & 0xff;
 	smp_num_siblings = ((ebx >> 8) & 0xff) + 1;
 
-	if (c->x86 == 0x15)
-		c->cu_id = ebx & 0xff;
-
-	if (c->x86 >= 0x17) {
-		c->cpu_core_id = ebx & 0xff;
-
-		if (smp_num_siblings > 1)
-			c->x86_max_cores /= smp_num_siblings;
-	}
+	switch (c->x86) {
+	case 0x17: {
+		u32 tmp, ccx_offset, cpu_offset;
 
-	/*
-	 * 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) {
+		/*
+		 * In family 17h, the CPUID_Fn8000001E_EBX[7:0] (CoreId)
+		 * is non-contiguous in downcore and non-SMT cases.
+		 * Fixup the cpu_core_id to be contiguous for cores within
+		 * the die.
+		 */
+		tmp = ebx & 0xff;
+		if (smp_num_siblings == 1) {
 			/*
-			 * LLC is at the core complex level.
-			 * Core complex id is ApicId[3].
+			 * CoreId bit-encoding for SMT-disabled
+			 * [7:4] : die
+			 * [3]   : ccx
+			 * [2:0] : core
 			 */
-			per_cpu(cpu_llc_id, cpu) = c->apicid >> 3;
+			ccx_offset = ((tmp >> 3) & 1) * l3_nshared;
+			cpu_offset = tmp & 7;
 		} else {
-			/* LLC is at the node level. */
+			/*
+			 * CoreId bit-encoding for SMT-enabled
+			 * [7:3] : die
+			 * [2]   : ccx
+			 * [1:0] : core
+			 */
+			ccx_offset = ((tmp >> 2) & 1) * l3_nshared /
+				       smp_num_siblings;
+			cpu_offset = tmp & 3;
+			c->x86_max_cores /= smp_num_siblings;
+
+		}
+		c->cpu_core_id = ccx_offset + cpu_offset;
+
+		/*
+		 * Family17h L3 cache (LLC) is at Core Complex (CCX).
+		 * There could be multiple CCXs in a node.
+		 * CCX ID is ApicId[3].
+		 */
+		per_cpu(cpu_llc_id, cpu) = c->apicid >> 3;
+
+		pr_debug("Fixup coreid:%#x to cpu_core_id:%#x\n",
+			 tmp, c->cpu_core_id);
+		break;
+	}
+	case 0x15:
+		c->cu_id = ebx & 0xff;
+		/* Follow through */
+	default:
+		/* LLC is default to L3, which generally per-node */
+		if (l3_nshared > 0) {
+			u8 node_id = ecx & 0xff;
+
 			per_cpu(cpu_llc_id, cpu) = node_id;
 		}
 	}
-- 
2.7.4