2 files changed, 21 insertions, 13 deletions

diff --git a/arch/i386/kernel/cpu/amd.c b/arch/i386/kernel/cpu/amd.c
index 786d1a57048b..b9c93d9789e7 100644
--- a/arch/i386/kernel/cpu/amd.c
+++ b/arch/i386/kernel/cpu/amd.c
@@ -224,15 +224,17 @@ static void __init init_amd(struct cpuinfo_x86 *c)
 
 #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",
diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index fb850b52b4da..1cb3e21c571a 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -873,10 +873,18 @@ static void __init amd_detect_cmp(struct cpuinfo_x86 *c)
         int node = 0;
         unsigned apicid = hard_smp_processor_id();
 #endif
+        unsigned ecx = cpuid_ecx(0x80000008);
 
-        bits = 0;
-        while ((1 << bits) < c->x86_max_cores)
-                bits++;
+        c->x86_max_cores = (ecx & 0xff) + 1;
+
+        /* CPU telling us the core id bits shift? */
+        bits = (ecx >> 12) & 0xF;
+
+        /* Otherwise recompute */
+        if (bits == 0) {
+                while ((1 << bits) < c->x86_max_cores)
+                        bits++;
+        }
 
         /* Low order bits define the core id (index of core in socket) */
         cpu_core_id[cpu] = phys_proc_id[cpu] & ((1 << bits)-1);
@@ -964,11 +972,9 @@ static int __init init_amd(struct cpuinfo_x86 *c)
         if (c->x86_power & (1<<8))
                 set_bit(X86_FEATURE_CONSTANT_TSC, &c->x86_capability);
 
-        if (c->extended_cpuid_level >= 0x80000008) {
-                c->x86_max_cores = (cpuid_ecx(0x80000008) & 0xff) + 1;
-
+        /* Multi core CPU? */
+        if (c->extended_cpuid_level >= 0x80000008)
                 amd_detect_cmp(c);
-        }
 
         return r;
 }