x86: Disabling x2apic if nox2apic is specified

Index: linux-2.6/arch/x86/include/asm/apic.h
===================================================================
@@ -176,6 +176,7 @@ static inline u64 native_x2apic_icr_read
 }
 
 extern int x2apic_phys;
+extern int nox2apic;
 extern void check_x2apic(void);
 extern void enable_x2apic(void);
 extern void x2apic_icr_write(u32 low, u32 id);

@@ -186,6 +187,10 @@ static inline int x2apic_enabled(void)
 	if (!cpu_has_x2apic)
 		return 0;
 
+	/* avoid to read msr */
+	if (nox2apic)
+		return 0;
+
 	rdmsr(MSR_IA32_APICBASE, msr, msr2);
 	if (msr & X2APIC_ENABLE)
 		return 1;

@@ -214,6 +219,7 @@ static inline void x2apic_force_phys(voi
 
 #define	x2apic_preenabled 0
 #define	x2apic_supported()	0
+#define	nox2apic	1
 #endif
 
 extern void enable_IR_x2apic(void);

Index: linux-2.6/arch/x86/kernel/acpi/boot.c
===================================================================
@@ -213,6 +213,8 @@ static int __init
 acpi_parse_x2apic(struct acpi_subtable_header *header, const unsigned long end)
 {
 	struct acpi_madt_local_x2apic *processor = NULL;
+	int apic_id;
+	u8 enabled;
 
 	processor = (struct acpi_madt_local_x2apic *)header;
 

@@ -221,6 +223,8 @@ acpi_parse_x2apic(struct acpi_subtable_h
 
 	acpi_table_print_madt_entry(header);
 
+	apic_id = processor->local_apic_id;
+	enabled = processor->lapic_flags & ACPI_MADT_ENABLED;
 #ifdef CONFIG_X86_X2APIC
 	/*
 	 * We need to register disabled CPU as well to permit

@@ -229,8 +233,10 @@ acpi_parse_x2apic(struct acpi_subtable_h
 	 * to not preallocating memory for all NR_CPUS
 	 * when we use CPU hotplug.
 	 */
-	acpi_register_lapic(processor->local_apic_id,	/* APIC ID */
-			    processor->lapic_flags & ACPI_MADT_ENABLED);
+	if (nox2apic && (apic_id >= 0xff) && enabled)
+		printk(KERN_WARNING PREFIX "x2apic entry ignored\n");
+	else
+		acpi_register_lapic(apic_id, enabled);
 #else
 	printk(KERN_WARNING PREFIX "x2apic entry ignored\n");
 #endif

112 lines not on this page · raw message

Index: linux-2.6/arch/x86/mm/srat_64.c
===================================================================
@@ -125,6 +125,13 @@ acpi_numa_x2apic_affinity_init(struct ac
 	if ((pa->flags & ACPI_SRAT_CPU_ENABLED) == 0)
 		return;
 	pxm = pa->proximity_domain;
+	apic_id = pa->apic_id;
+#ifdef CONFIG_X86_X2APIC
+	if (nox2apic && (apic_id >= 0xff)) {
+		printk(KERN_INFO "SRAT: PXM %u -> X2APIC 0x%04x ignored\n",
+			 pxm, apic_id);
+		return;
+	}
 	node = setup_node(pxm);
 	if (node < 0) {
 		printk(KERN_ERR "SRAT: Too many proximity domains %x\n", pxm);

@@ -132,12 +139,15 @@ acpi_numa_x2apic_affinity_init(struct ac
 		return;
 	}
 
-	apic_id = pa->apic_id;
 	apicid_to_node[apic_id] = node;
 	node_set(node, cpu_nodes_parsed);
 	acpi_numa = 1;
 	printk(KERN_INFO "SRAT: PXM %u -> APIC 0x%04x -> Node %u\n",
 	       pxm, apic_id, node);
+#else
+	printk(KERN_INFO "SRAT: PXM %u -> X2APIC 0x%04x ignored\n",
+		 pxm, apic_id);
+#endif
 }
 
 /* Callback for Proximity Domain -> LAPIC mapping */

Index: linux-2.6/arch/x86/include/asm/apicdef.h
===================================================================
@@ -140,6 +140,7 @@
 
 #define APIC_BASE (fix_to_virt(FIX_APIC_BASE))
 #define APIC_BASE_MSR	0x800
+#define XAPIC_ENABLE	(1UL << 11)
 #define X2APIC_ENABLE	(1UL << 10)
 
 #ifdef CONFIG_X86_32