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authorMike Travis <travis@sgi.com>2008-12-18 02:21:39 +0300
committerIngo Molnar <mingo@elte.hu>2008-12-18 14:08:05 +0300
commit3b11ce7f542e415c90267b4482d4611410b468e6 (patch)
tree26366b9f25af830b71c78504bbadd94896a8b82a
parenta775a38b1353161a6d7af86b667d6523c12c1a37 (diff)
downloadlinux-3b11ce7f542e415c90267b4482d4611410b468e6.tar.xz
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>
-rw-r--r--Documentation/cpu-hotplug.txt17
-rw-r--r--arch/x86/kernel/apic.c20
-rw-r--r--arch/x86/kernel/smpboot.c25
3 files changed, 42 insertions, 20 deletions
diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index 94bbc27ddd4f..9d620c153b04 100644
--- a/Documentation/cpu-hotplug.txt
+++ b/Documentation/cpu-hotplug.txt
@@ -50,16 +50,17 @@ additional_cpus=n (*) Use this to limit hotpluggable cpus. This option sets
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.
diff --git a/arch/x86/kernel/apic.c b/arch/x86/kernel/apic.c
index 93cf2d13f335..f7a32a3beb2f 100644
--- a/arch/x86/kernel/apic.c
+++ b/arch/x86/kernel/apic.c
@@ -1819,28 +1819,32 @@ void disconnect_bsp_APIC(int virt_wire_setup)
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) {
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index be9466788043..1a9941b11150 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1252,6 +1252,15 @@ void __init native_smp_cpus_done(unsigned int max_cpus)
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 @@ void __init native_smp_cpus_done(unsigned int max_cpus)
*
* 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 @@ __init void prefill_possible_map(void)
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));