x86: convert cpu_to_apicid to be a per cpu variable

This patch converts the x86_cpu_to_apicid array to be a per cpu
variable. This saves sizeof(apicid) * NR unused cpus.  Access is mostly
from startup and CPU HOTPLUG functions.

MP_processor_info() is one of the functions that require access to the
x86_cpu_to_apicid array before the per_cpu data area is setup.  For this
case, a pointer to the __initdata array is initialized in setup_arch()
and removed in smp_prepare_cpus() after the per_cpu data area is
initialized.

A second change is included to change the initial array value of ARCH
i386 from 0xff to BAD_APICID to be consistent with ARCH x86_64.

Signed-off-by: Mike Travis <travis@sgi.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 22 insertions, 1 deletions

diff --git a/arch/x86/kernel/smpboot_64.c b/arch/x86/kernel/smpboot_64.c
index e351ac4ab5b1..c3e8668c5278 100644
--- a/arch/x86/kernel/smpboot_64.c
+++ b/arch/x86/kernel/smpboot_64.c
@@ -694,7 +694,7 @@ do_rest:
                 clear_node_cpumask(cpu); /* was set by numa_add_cpu */
                 cpu_clear(cpu, cpu_present_map);
                 cpu_clear(cpu, cpu_possible_map);
-                x86_cpu_to_apicid[cpu] = BAD_APICID;
+                per_cpu(x86_cpu_to_apicid, cpu) = BAD_APICID;
                 return -EIO;
         }
 
@@ -841,6 +841,26 @@ static int __init smp_sanity_check(unsigned max_cpus)
 }
 
 /*
+ * Copy apicid's found by MP_processor_info from initial array to the per cpu
+ * data area.  The x86_cpu_to_apicid_init array is then expendable and the
+ * x86_cpu_to_apicid_ptr is zeroed indicating that the static array is no
+ * longer available.
+ */
+void __init smp_set_apicids(void)
+{
+        int cpu;
+
+        for_each_cpu_mask(cpu, cpu_possible_map) {
+                if (per_cpu_offset(cpu))
+                        per_cpu(x86_cpu_to_apicid, cpu) =
+                                                x86_cpu_to_apicid_init[cpu];
+        }
+
+        /* indicate the static array will be going away soon */
+        x86_cpu_to_apicid_ptr = NULL;
+}
+
+/*
  * Prepare for SMP bootup.  The MP table or ACPI has been read
  * earlier.  Just do some sanity checking here and enable APIC mode.
  */
@@ -849,6 +869,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
         nmi_watchdog_default();
         current_cpu_data = boot_cpu_data;
         current_thread_info()->cpu = 0;  /* needed? */
+        smp_set_apicids();
         set_cpu_sibling_map(0);
 
         if (smp_sanity_check(max_cpus) < 0) {