[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 (file)
--- 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 fb850b5..1cb3e21 100644 (file)
--- 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;
 }