[PATCH] x86_64: Support more than 8 cores on AMD systems
Use physical mode instead of logical mode to address more CPUs. This is also
used in the CPU hotplug case to avoid a race.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/x86_64/kernel/genapic.c b/arch/x86_64/kernel/genapic.c
index 69b9c25..30c843a 100644
--- a/arch/x86_64/kernel/genapic.c
+++ b/arch/x86_64/kernel/genapic.c
@@ -31,6 +31,7 @@
extern struct genapic apic_cluster;
extern struct genapic apic_flat;
+extern struct genapic apic_physflat;
struct genapic *genapic = &apic_flat;
@@ -44,12 +45,7 @@
u8 clusters, max_cluster;
u8 id;
u8 cluster_cnt[NUM_APIC_CLUSTERS];
-
- if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
- /* AMD always uses flat mode right now */
- genapic = &apic_flat;
- goto print;
- }
+ int num_cpus = 0;
#if defined(CONFIG_ACPI_BUS)
/*
@@ -64,15 +60,34 @@
#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;
+ num_cpus++;
+ 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_CPU_HOTPLUG
+ /* 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 (num_cpus <= 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;