[PATCH] x86-64: Use physflat on Intel for < 8 CPUs with CPU hotplug

[pandora-kernel.git] / arch / x86_64 / kernel / genapic.c

diff --git a/arch/x86_64/kernel/genapic.c b/arch/x86_64/kernel/genapic.c
index 69b9c25..7a64ea1 100644 (file)
--- a/arch/x86_64/kernel/genapic.c
+++ b/arch/x86_64/kernel/genapic.c
@@ -20,17 +20,18 @@
 #include <asm/smp.h>
 #include <asm/ipi.h>
 
-#if defined(CONFIG_ACPI_BUS)
+#if defined(CONFIG_ACPI)
 #include <acpi/acpi_bus.h>
 #endif
 
 /* which logical CPU number maps to which CPU (physical APIC ID) */
-u8 x86_cpu_to_apicid[NR_CPUS] = { [0 ... NR_CPUS-1] = BAD_APICID };
+u8 x86_cpu_to_apicid[NR_CPUS] __read_mostly = { [0 ... NR_CPUS-1] = BAD_APICID };
 EXPORT_SYMBOL(x86_cpu_to_apicid);
 u8 x86_cpu_to_log_apicid[NR_CPUS] = { [0 ... NR_CPUS-1] = BAD_APICID };
 
 extern struct genapic apic_cluster;
 extern struct genapic apic_flat;
+extern struct genapic apic_physflat;
 
 struct genapic *genapic = &apic_flat;
 
@@ -44,14 +45,9 @@ void __init clustered_apic_check(void)
        u8 clusters, max_cluster;
        u8 id;
        u8 cluster_cnt[NUM_APIC_CLUSTERS];
+       int max_apic = 0;
 
-       if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
-               /* AMD always uses flat mode right now */
-               genapic = &apic_flat;
-               goto print;
-       }
-
-#if defined(CONFIG_ACPI_BUS)
+#if defined(CONFIG_ACPI)
        /*
         * Some x86_64 machines use physical APIC mode regardless of how many
         * procs/clusters are present (x86_64 ES7000 is an example).
@@ -64,15 +60,35 @@ void __init clustered_apic_check(void)
 #endif
 
        memset(cluster_cnt, 0, sizeof(cluster_cnt));
-
        for (i = 0; i < NR_CPUS; i++) {
                id = bios_cpu_apicid[i];
-               if (id != BAD_APICID)
-                       cluster_cnt[APIC_CLUSTERID(id)]++;
+               if (id == BAD_APICID)
+                       continue;
+               if (id > max_apic)
+                       max_apic = id;
+               cluster_cnt[APIC_CLUSTERID(id)]++;
        }
 
+       /* Don't use clustered mode on AMD platforms. */
+       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
+               goto print;
+       }
+
        clusters = 0;
        max_cluster = 0;
+
        for (i = 0; i < NUM_APIC_CLUSTERS; i++) {
                if (cluster_cnt[i] > 0) {
                        ++clusters;
@@ -88,9 +104,14 @@ 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)
+       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
                genapic = &apic_flat;
-       else
+#endif
+       } else
                genapic = &apic_cluster;
 
 print: