Intel systems with more than 8 CPUs require that the APIC is configured

in clustered mode with the apic=bigsmp kernel parameter. This patch does
the APIC mode selection automatically without needing to manually specify
the kernel paremeter.

(KAF note: I see the patch is also present in Linux 2.6.14.2)

Signed-off-by: Nitin Kamble <nitin.a.kamble@intel.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>

xen/arch/x86/acpi/boot.c

@@ -602,7 +602,8 @@ acpi_process_madt(void)
 		error = acpi_parse_madt_lapic_entries();
 		if (!error) {
 			acpi_lapic = 1;
-
+			generic_bigsmp_probe();
+ 
 			/*
 			 * Parse MADT IO-APIC entries
 			 */

xen/arch/x86/genapic/bigsmp.c

@@ -45,7 +45,10 @@ static struct dmi_system_id __initdata bigsmp_dmi_table[] = {
 
 static __init int probe_bigsmp(void)
 { 
-	dmi_check_system(bigsmp_dmi_table);
+	if (def_to_bigsmp)
+		dmi_bigsmp = 1;
+	else
+		dmi_check_system(bigsmp_dmi_table);
 	return dmi_bigsmp; 
 } 
 

xen/arch/x86/genapic/probe.c

@@ -29,6 +29,25 @@ struct genapic *apic_probe[] __initdata = {
 	NULL,
 };
 
+static int cmdline_apic;
+
+void __init generic_bigsmp_probe(void)
+{
+	/*
+	 * This routine is used to switch to bigsmp mode when
+	 * - There is no apic= option specified by the user
+	 * - generic_apic_probe() has choosen apic_default as the sub_arch
+	 * - we find more than 8 CPUs in acpi LAPIC listing with xAPIC support
+	 */
+
+	if (!cmdline_apic && genapic == &apic_default)
+		if (apic_bigsmp.probe()) {
+			genapic = &apic_bigsmp;
+			printk(KERN_INFO "Overriding APIC driver with %s\n",
+			       genapic->name);
+		}
+}
+
 static void __init genapic_apic_force(char *str)
 {
 	int i;
@@ -41,7 +60,7 @@ custom_param("apic", genapic_apic_force);
 void __init generic_apic_probe(void) 
 { 
 	int i;
-	int changed = (genapic != NULL);
+	int changed = cmdline_apic = (genapic != NULL);
 
 	for (i = 0; !changed && apic_probe[i]; i++) { 
 		if (apic_probe[i]->probe()) {

xen/arch/x86/mpparse.c

@@ -63,6 +63,8 @@ int nr_ioapics;
 int pic_mode;
 unsigned long mp_lapic_addr;
 
+unsigned int def_to_bigsmp;
+
 /* Processor that is doing the boot up */
 unsigned int boot_cpu_physical_apicid = -1U;
 unsigned int boot_cpu_logical_apicid = -1U;
@@ -213,6 +215,13 @@ void __init MP_processor_info (struct mpc_config_processor *m)
 		ver = 0x10;
 	}
 	apic_version[m->mpc_apicid] = ver;
+	if ((num_processors > 8) &&
+	    APIC_XAPIC(ver) &&
+	    (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL))
+		def_to_bigsmp = 1;
+	else
+		def_to_bigsmp = 0;
+
 	bios_cpu_apicid[num_processors - 1] = m->mpc_apicid;
 }
 

xen/include/asm-x86/apicdef.h

@@ -16,6 +16,7 @@
 #define			GET_APIC_VERSION(x)	((x)&0xFF)
 #define			GET_APIC_MAXLVT(x)	(((x)>>16)&0xFF)
 #define			APIC_INTEGRATED(x)	((x)&0xF0)
+#define			APIC_XAPIC(x)		((x) >= 0x14)
 #define		APIC_TASKPRI	0x80
 #define			APIC_TPRI_MASK		0xFF
 #define		APIC_ARBPRI	0x90

xen/include/asm-x86/mach-generic/mach_apic.h

@@ -28,4 +28,6 @@
 #define enable_apic_mode (genapic->enable_apic_mode)
 #define phys_pkg_id (genapic->phys_pkg_id)
 
+extern void generic_bigsmp_probe(void);
+
 #endif /* __ASM_MACH_APIC_H */

xen/include/asm-x86/mpspec.h

@@ -11,6 +11,7 @@ extern int mp_bus_id_to_local [MAX_MP_BUSSES];
 extern int quad_local_to_mp_bus_id [NR_CPUS/4][4];
 extern int mp_bus_id_to_pci_bus [MAX_MP_BUSSES];
 
+extern unsigned int def_to_bigsmp;
 extern unsigned int boot_cpu_physical_apicid;
 extern int smp_found_config;
 extern void find_smp_config (void);