[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/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index fb850b5..1cb3e21 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -873,10 +873,18 @@
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 @@
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;
}