1 files changed, 15 insertions, 24 deletions

diff --git a/arch/x86_64/kernel/genapic.c b/arch/x86_64/kernel/genapic.c
index 7312ddb84fb4..2f2b8fc6e2f3 100644
--- a/arch/x86_64/kernel/genapic.c
+++ b/arch/x86_64/kernel/genapic.c
@@ -32,21 +32,20 @@ extern struct genapic apic_cluster;
 extern struct genapic apic_flat;
 extern struct genapic apic_physflat;
 
-struct genapic *genapic = &apic_flat;
-
+struct genapic __read_mostly *genapic = &apic_flat;
 
 /*
  * Check the APIC IDs in bios_cpu_apicid and choose the APIC mode.
  */
 void __init clustered_apic_check(void)
 {
-        long i;
+        int i;
         u8 clusters, max_cluster;
         u8 id;
         u8 cluster_cnt[NUM_APIC_CLUSTERS];
         int max_apic = 0;
 
-#if defined(CONFIG_ACPI)
+#ifdef CONFIG_ACPI
         /*
          * Some x86_64 machines use physical APIC mode regardless of how many
          * procs/clusters are present (x86_64 ES7000 is an example).
@@ -68,20 +67,17 @@ void __init clustered_apic_check(void)
                 cluster_cnt[APIC_CLUSTERID(id)]++;
         }
 
-        /* Don't use clustered mode on AMD platforms. */
+        /*
+         * Don't use clustered mode on AMD platforms, default
+         * to flat logical mode.
+         */
         if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
-                genapic = &apic_physflat;
-#ifndef CONFIG_HOTPLUG_CPU
-                /* In the CPU hotplug case we cannot use broadcast mode
-                   because that opens a race when a CPU is removed.
-                   Stay at physflat mode in this case.
-                   It is bad to do this unconditionally though. Once
-                   we have ACPI platform support for CPU hotplug
-                   we should detect hotplug capablity from ACPI tables and
-                   only do this when really needed. -AK */
-                if (max_apic <= 8)
-                        genapic = &apic_flat;
-#endif
+                /*
+                 * Switch to physical flat mode if more than 8 APICs
+                 * (In the case of 8 CPUs APIC ID goes from 0 to 7):
+                 */
+                if (max_apic >= 8)
+                        genapic = &apic_physflat;
                 goto print;
         }
 
@@ -103,14 +99,9 @@ void __init clustered_apic_check(void)
          * (We don't use lowest priority delivery + HW APIC IRQ steering, so
          * can ignore the clustered logical case and go straight to physical.)
          */
-        if (clusters <= 1 && max_cluster <= 8 && cluster_cnt[0] == max_cluster) {
-#ifdef CONFIG_HOTPLUG_CPU
-                /* Don't use APIC shortcuts in CPU hotplug to avoid races */
-                genapic = &apic_physflat;
-#else
+        if (clusters <= 1 && max_cluster <= 8 && cluster_cnt[0] == max_cluster)
                 genapic = &apic_flat;
-#endif
-        } else
+        else
                 genapic = &apic_cluster;
 
 print: