Use the APIC to determine the hardware processor id - x86_64

hard_smp_processor_id used to be just a macro that hard-coded
hard_smp_processor_id to 0 in the non SMP case.  When booting non SMP kernels
on hardware where the boot ioapic id is not 0 this turns out to be a problem.
This is happens frequently in the case of kdump and once in a great while in
the case of real hardware.

Use the APIC to determine the hardware processor id in both UP and SMP kernels
to fix this issue.

Notice that hard_smp_processor_id is only used by SMP code or by code that
works with apics so we do not need to handle the case when apics are not
present and hard_smp_processor_id should never be called there.

Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Cc: "Luck, Tony" <tony.luck@intel.com>
Acked-by: Andi Kleen <ak@suse.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 8 deletions

diff --git a/include/asm-x86_64/smp.h b/include/asm-x86_64/smp.h
index f62fda527439..3f303d2365ed 100644
--- a/include/asm-x86_64/smp.h
+++ b/include/asm-x86_64/smp.h
@@ -57,12 +57,6 @@ static inline int num_booting_cpus(void)
 
 #define raw_smp_processor_id() read_pda(cpunumber)
 
-static inline int hard_smp_processor_id(void)
-{
-        /* we don't want to mark this access volatile - bad code generation */
-        return GET_APIC_ID(*(unsigned int *)(APIC_BASE+APIC_ID));
-}
-
 extern int __cpu_disable(void);
 extern void __cpu_die(unsigned int cpu);
 extern void prefill_possible_map(void);
@@ -71,10 +65,14 @@ extern unsigned __cpuinitdata disabled_cpus;
 
 #define NO_PROC_ID              0xFF            /* No processor magic marker */
 
-#else /* CONFIG_SMP */
-#define hard_smp_processor_id() 0
 #endif /* CONFIG_SMP */
 
+static inline int hard_smp_processor_id(void)
+{
+        /* we don't want to mark this access volatile - bad code generation */
+        return GET_APIC_ID(*(unsigned int *)(APIC_BASE+APIC_ID));
+}
+
 /*
  * Some lowlevel functions might want to know about
  * the real APIC ID <-> CPU # mapping.