x86: use possible_cpus=NUM to extend the possible cpus allowed

Impact: add new boot parameter Use possible_cpus=NUM kernel parameter to extend the number of possible cpus. The ability to HOTPLUG ON cpus that are "possible" but not "present" is dealt with in a later patch. Signed-off-by: Mike Travis <travis@sgi.com>

x86: use possible_cpus=NUM to extend the possible cpus allowed
Impact: add new boot parameter Use possible_cpus=NUM kernel parameter to extend the number of possible cpus. The ability to HOTPLUG ON cpus that are "possible" but not "present" is dealt with in a later patch. Signed-off-by: Mike Travis <travis@sgi.com>
Mike Travis · Ingo Molnar
1 parent a775a38b13
Showing 3 changed files with 42 additions and 20 deletions Side-by-side Diff
Documentation/cpu-hotplug.txt
arch/x86/kernel/apic.c
arch/x86/kernel/smpboot.c
@@ -50,16 +50,17 @@
   			cpu_possible_map = cpu_present_map + additional_cpus
  
 (*) Option valid only for following architectures
-- x86_64, ia64
+- ia64
  
-ia64 and x86_64 use the number of disabled local apics in ACPI tables MADT
-to determine the number of potentially hot-pluggable cpus. The implementation
-should only rely on this to count the # of cpus, but *MUST* not rely on the
-apicid values in those tables for disabled apics. In the event BIOS doesn't
-mark such hot-pluggable cpus as disabled entries, one could use this
-parameter "additional_cpus=x" to represent those cpus in the cpu_possible_map.
+ia64 uses the number of disabled local apics in ACPI tables MADT to
+determine the number of potentially hot-pluggable cpus. The implementation
+should only rely on this to count the # of cpus, but *MUST* not rely
+on the apicid values in those tables for disabled apics. In the event
+BIOS doesn't mark such hot-pluggable cpus as disabled entries, one could
+use this parameter "additional_cpus=x" to represent those cpus in the
+cpu_possible_map.
  
-possible_cpus=n		[s390 only] use this to set hotpluggable cpus.
+possible_cpus=n		[s390,x86_64] use this to set hotpluggable cpus.
 			This option sets possible_cpus bits in
 			cpu_possible_map. Thus keeping the numbers of bits set
 			constant even if the machine gets rebooted.
@@ -1819,28 +1819,32 @@
 void __cpuinit generic_processor_info(int apicid, int version)
 {
 	int cpu;
-	cpumask_t tmp_map;
  
 	/*
 	 * Validate version
 	 */
 	if (version == 0x0) {
 		pr_warning("BIOS bug, APIC version is 0 for CPU#%d! "
-			"fixing up to 0x10. (tell your hw vendor)\n",
-			version);
+			   "fixing up to 0x10. (tell your hw vendor)\n",
+				version);
 		version = 0x10;
 	}
 	apic_version[apicid] = version;
  
-	if (num_processors >= NR_CPUS) {
-		pr_warning("WARNING: NR_CPUS limit of %i reached."
-			"  Processor ignored.\n", NR_CPUS);
+	if (num_processors >= nr_cpu_ids) {
+		int max = nr_cpu_ids;
+		int thiscpu = max + disabled_cpus;
+
+		pr_warning(
+			"ACPI: NR_CPUS/possible_cpus limit of %i reached."
+			"  Processor %d/0x%x ignored.\n", max, thiscpu, apicid);
+
+		disabled_cpus++;
 		return;
 	}
  
 	num_processors++;
-	cpus_complement(tmp_map, cpu_present_map);
-	cpu = first_cpu(tmp_map);
+	cpu = cpumask_next_zero(-1, cpu_present_mask);
  
 	physid_set(apicid, phys_cpu_present_map);
 	if (apicid == boot_cpu_physical_apicid) {
@@ -1252,6 +1252,15 @@
 	check_nmi_watchdog();
 }
  
+static int __initdata setup_possible_cpus = -1;
+static int __init _setup_possible_cpus(char *str)
+{
+	get_option(&str, &setup_possible_cpus);
+	return 0;
+}
+early_param("possible_cpus", _setup_possible_cpus);
+
+
 /*
  * cpu_possible_map should be static, it cannot change as cpu's
  * are onlined, or offlined. The reason is per-cpu data-structures
@@ -1264,7 +1273,7 @@
  *
  * Three ways to find out the number of additional hotplug CPUs:
  * - If the BIOS specified disabled CPUs in ACPI/mptables use that.
- * - The user can overwrite it with additional_cpus=NUM
+ * - The user can overwrite it with possible_cpus=NUM
  * - Otherwise don't reserve additional CPUs.
  * We do this because additional CPUs waste a lot of memory.
  * -AK
@@ -1277,9 +1286,17 @@
 	if (!num_processors)
 		num_processors = 1;
  
-	possible = num_processors + disabled_cpus;
-	if (possible > NR_CPUS)
-		possible = NR_CPUS;
+	if (setup_possible_cpus == -1)
+		possible = num_processors + disabled_cpus;
+	else
+		possible = setup_possible_cpus;
+
+	if (possible > CONFIG_NR_CPUS) {
+		printk(KERN_WARNING
+			"%d Processors exceeds NR_CPUS limit of %d\n",
+			possible, CONFIG_NR_CPUS);
+		possible = CONFIG_NR_CPUS;
+	}
  
 	printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n",
 		possible, max_t(int, possible - num_processors, 0));
...	...	@@ -50,16 +50,17 @@
50	50	cpu_possible_map = cpu_present_map + additional_cpus
51	51
52	52	(*) Option valid only for following architectures
53		-- x86_64, ia64
	53	+- ia64
54	54
55		-ia64 and x86_64 use the number of disabled local apics in ACPI tables MADT
56		-to determine the number of potentially hot-pluggable cpus. The implementation
57		-should only rely on this to count the # of cpus, but MUST not rely on the
58		-apicid values in those tables for disabled apics. In the event BIOS doesn't
59		-mark such hot-pluggable cpus as disabled entries, one could use this
60		-parameter "additional_cpus=x" to represent those cpus in the cpu_possible_map.
	55	+ia64 uses the number of disabled local apics in ACPI tables MADT to
	56	+determine the number of potentially hot-pluggable cpus. The implementation
	57	+should only rely on this to count the # of cpus, but MUST not rely
	58	+on the apicid values in those tables for disabled apics. In the event
	59	+BIOS doesn't mark such hot-pluggable cpus as disabled entries, one could
	60	+use this parameter "additional_cpus=x" to represent those cpus in the
	61	+cpu_possible_map.
61	62
62		-possible_cpus=n [s390 only] use this to set hotpluggable cpus.
	63	+possible_cpus=n [s390,x86_64] use this to set hotpluggable cpus.
63	64	This option sets possible_cpus bits in
64	65	cpu_possible_map. Thus keeping the numbers of bits set
65	66	constant even if the machine gets rebooted.
...	...	@@ -1819,28 +1819,32 @@
1819	1819	void __cpuinit generic_processor_info(int apicid, int version)
1820	1820	{
1821	1821	int cpu;
1822		- cpumask_t tmp_map;
1823	1822
1824	1823	/*
1825	1824	* Validate version
1826	1825	*/
1827	1826	if (version == 0x0) {
1828	1827	pr_warning("BIOS bug, APIC version is 0 for CPU#%d! "
1829		- "fixing up to 0x10. (tell your hw vendor)\n",
1830		- version);
	1828	+ "fixing up to 0x10. (tell your hw vendor)\n",
	1829	+ version);
1831	1830	version = 0x10;
1832	1831	}
1833	1832	apic_version[apicid] = version;
1834	1833
1835		- if (num_processors >= NR_CPUS) {
1836		- pr_warning("WARNING: NR_CPUS limit of %i reached."
1837		- " Processor ignored.\n", NR_CPUS);
	1834	+ if (num_processors >= nr_cpu_ids) {
	1835	+ int max = nr_cpu_ids;
	1836	+ int thiscpu = max + disabled_cpus;
	1837	+
	1838	+ pr_warning(
	1839	+ "ACPI: NR_CPUS/possible_cpus limit of %i reached."
	1840	+ " Processor %d/0x%x ignored.\n", max, thiscpu, apicid);
	1841	+
	1842	+ disabled_cpus++;
1838	1843	return;
1839	1844	}
1840	1845
1841	1846	num_processors++;
1842		- cpus_complement(tmp_map, cpu_present_map);
1843		- cpu = first_cpu(tmp_map);
	1847	+ cpu = cpumask_next_zero(-1, cpu_present_mask);
1844	1848
1845	1849	physid_set(apicid, phys_cpu_present_map);
1846	1850	if (apicid == boot_cpu_physical_apicid) {
...	...	@@ -1252,6 +1252,15 @@
1252	1252	check_nmi_watchdog();
1253	1253	}
1254	1254
	1255	+static int __initdata setup_possible_cpus = -1;
	1256	+static int __init _setup_possible_cpus(char *str)
	1257	+{
	1258	+ get_option(&str, &setup_possible_cpus);
	1259	+ return 0;
	1260	+}
	1261	+early_param("possible_cpus", _setup_possible_cpus);
	1262	+
	1263	+
1255	1264	/*
1256	1265	* cpu_possible_map should be static, it cannot change as cpu's
1257	1266	* are onlined, or offlined. The reason is per-cpu data-structures
...	...	@@ -1264,7 +1273,7 @@
1264	1273	*
1265	1274	* Three ways to find out the number of additional hotplug CPUs:
1266	1275	* - If the BIOS specified disabled CPUs in ACPI/mptables use that.
1267		- * - The user can overwrite it with additional_cpus=NUM
	1276	+ * - The user can overwrite it with possible_cpus=NUM
1268	1277	* - Otherwise don't reserve additional CPUs.
1269	1278	* We do this because additional CPUs waste a lot of memory.
1270	1279	* -AK
...	...	@@ -1277,9 +1286,17 @@
1277	1286	if (!num_processors)
1278	1287	num_processors = 1;
1279	1288
1280		- possible = num_processors + disabled_cpus;
1281		- if (possible > NR_CPUS)
1282		- possible = NR_CPUS;
	1289	+ if (setup_possible_cpus == -1)
	1290	+ possible = num_processors + disabled_cpus;
	1291	+ else
	1292	+ possible = setup_possible_cpus;
	1293	+
	1294	+ if (possible > CONFIG_NR_CPUS) {
	1295	+ printk(KERN_WARNING
	1296	+ "%d Processors exceeds NR_CPUS limit of %d\n",
	1297	+ possible, CONFIG_NR_CPUS);
	1298	+ possible = CONFIG_NR_CPUS;
	1299	+ }
1283	1300
1284	1301	printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n",
1285	1302	possible, max_t(int, possible - num_processors, 0));