From e6cfae450e1541792b9c015a8c25182015b096dc Mon Sep 17 00:00:00 2001
From: Pawel Dziepak <pdziepak@quarnos.org>
Date: Sun, 2 Feb 2014 23:36:42 +0000
Subject: [PATCH] kernel/x86: Make x2APIC CPU topology detection more future
 proof

The main reason for this patch is to fix gcc 4.8.2 warning about
hierarchyLevels possibly being used not initialized. Such thing
actually can not happen since all x2APIC CPUs are aware of at least
3 topology levels. However, once more topology levels are introduced
we will have to deal with CPUs that do not report information about all
of them.
---
 src/system/kernel/arch/x86/arch_cpu.cpp | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/system/kernel/arch/x86/arch_cpu.cpp b/src/system/kernel/arch/x86/arch_cpu.cpp
index 594dba680b..93d58f81e4 100644
--- a/src/system/kernel/arch/x86/arch_cpu.cpp
+++ b/src/system/kernel/arch/x86/arch_cpu.cpp
@@ -622,11 +622,11 @@ detect_intel_cpu_topology_x2apic(uint32 maxBasicLeaf)
 	if (maxBasicLeaf < 11)
 		return B_UNSUPPORTED;
 
-	uint8 hierarchyLevels[CPU_TOPOLOGY_LEVELS];
+	uint8 hierarchyLevels[CPU_TOPOLOGY_LEVELS] = { 0 };
 
 	int currentLevel = 0;
 	int levelType;
-	int levelsSet = 0;
+	unsigned int levelsSet = 0;
 
 	do {
 		cpuid_info cpuid;
@@ -635,13 +635,15 @@ detect_intel_cpu_topology_x2apic(uint32 maxBasicLeaf)
 			return B_UNSUPPORTED;
 
 		levelType = (cpuid.regs.ecx >> 8) & 0xff;
+		int levelValue = cpuid.regs.eax & 0x1f;
+
 		switch (levelType) {
 			case 1:	// SMT
-				hierarchyLevels[CPU_TOPOLOGY_SMT] = cpuid.regs.eax & 0x1f;
+				hierarchyLevels[CPU_TOPOLOGY_SMT] = levelValue;
 				levelsSet |= 1;
 				break;
 			case 2:	// core
-				hierarchyLevels[CPU_TOPOLOGY_CORE] = cpuid.regs.eax & 0x1f;
+				hierarchyLevels[CPU_TOPOLOGY_CORE] = levelValue;
 				levelsSet |= 2;
 				break;
 		}
@@ -651,10 +653,16 @@ detect_intel_cpu_topology_x2apic(uint32 maxBasicLeaf)
 
 	sGetCPUTopologyID = get_intel_cpu_initial_x2apic_id;
 
+	for (int i = 1; i < CPU_TOPOLOGY_LEVELS; i++) {
+		if ((levelsSet & (1u << i)) != 0)
+			continue;
+		hierarchyLevels[i] = hierarchyLevels[i - 1];
+	}
+
 	for (int i = 0; i < CPU_TOPOLOGY_LEVELS; i++) {
 		uint32 mask = ~uint32(0);
 		if (i < CPU_TOPOLOGY_LEVELS - 1)
-			mask = (1 << hierarchyLevels[i]) - 1;
+			mask = (1u << hierarchyLevels[i]) - 1;
 		if (i > 0)
 			mask &= ~sHierarchyMask[i - 1];
 		sHierarchyMask[i] = mask;