[PATCH] Add the vgetcpu vsyscall

This patch adds a vgetcpu vsyscall, which depending on the CPU RDTSCP
capability uses either the RDTSCP or CPUID to obtain a CPU and node
numbers and pass them to the program.

AK: Lots of changes over Vojtech's original code:
Better prototype for vgetcpu()
It's better to pass the cpu / node numbers as separate arguments
to avoid mistakes when going from SMP to NUMA.
Also add a fast time stamp based cache using a user supplied
argument to speed things more up.
Use fast method from Chuck Ebbert to retrieve node/cpu from
GDT limit instead of CPUID
Made sure RDTSCP init is always executed after node is known.
Drop printk

Signed-off-by: Vojtech Pavlik <vojtech@suse.cz>
Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S
index c9739ca81d06..505ec4a57506 100644
--- a/arch/x86_64/kernel/head.S
+++ b/arch/x86_64/kernel/head.S
@@ -371,7 +371,7 @@ ENTRY(cpu_gdt_table)
         .quad   0,0                     /* TSS */
         .quad   0,0                     /* LDT */
         .quad   0,0,0                   /* three TLS descriptors */ 
-        .quad   0                       /* unused */
+        .quad   0x0000f40000000000      /* node/CPU stored in limit */
 gdt_end:        
         /* asm/segment.h:GDT_ENTRIES must match this */ 
         /* This should be a multiple of the cache line size */