[PATCH] i386/x86-64: Use new official CPUID to get APICID/core split on AMD platforms
Previously the apicid<->coreid split was computed based on the max
number of cores. Now use a new CPUID AMD defined for that. On most
systems right now it should be 0 and the old method will be used.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/i386/kernel/cpu/amd.c b/arch/i386/kernel/cpu/amd.c
index 786d1a5..b9c93d9 100644
--- a/arch/i386/kernel/cpu/amd.c
+++ b/arch/i386/kernel/cpu/amd.c
@@ -224,15 +224,17 @@
#ifdef CONFIG_X86_HT
/*
- * On a AMD dual core setup the lower bits of the APIC id
- * distingush the cores. Assumes number of cores is a power
- * of two.
+ * On a AMD multi core setup the lower bits of the APIC id
+ * distingush the cores.
*/
if (c->x86_max_cores > 1) {
int cpu = smp_processor_id();
- unsigned bits = 0;
- while ((1 << bits) < c->x86_max_cores)
- bits++;
+ unsigned bits = (cpuid_ecx(0x80000008) >> 12) & 0xf;
+
+ if (bits == 0) {
+ while ((1 << bits) < c->x86_max_cores)
+ bits++;
+ }
cpu_core_id[cpu] = phys_proc_id[cpu] & ((1<<bits)-1);
phys_proc_id[cpu] >>= bits;
printk(KERN_INFO "CPU %d(%d) -> Core %d\n",