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>

diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index 94bbc27ddd4fbf50ff361177450c5f524210f1cb..9d620c153b04f2469bf664e6489e3af6817663e2 100644 (file)
--- 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 93cf2d13f335097c00f02f6e48ad280726f2778f..f7a32a3beb2f39f9683ccab8e6ac058680e9a789 100644 (file)
--- 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 be9466788043c1bb00e435cb9bb11eb0544436fb..1a9941b111504dc6de7084d662ef56a938a46797 100644 (file)
--- 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));