[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, 7 insertions, 6 deletions

diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 97b9e46d1992..560ed944dc0e 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -899,12 +899,8 @@ static int __cpuinit
 time_cpu_notifier(struct notifier_block *nb, unsigned long action, void *hcpu)
 {
         unsigned cpu = (unsigned long) hcpu;
-        if (action == CPU_ONLINE &&
-                cpu_has(&cpu_data[cpu], X86_FEATURE_RDTSCP)) {
-                unsigned p;
-                p = smp_processor_id() | (cpu_to_node(smp_processor_id())<<12);
-                write_rdtscp_aux(p);
-        }
+        if (action == CPU_ONLINE)
+                vsyscall_set_cpu(cpu);
         return NOTIFY_DONE;
 }
 
@@ -993,6 +989,11 @@ void time_init_gtod(void)
         if (unsynchronized_tsc())
                 notsc = 1;
 
+        if (cpu_has(&boot_cpu_data, X86_FEATURE_RDTSCP))
+                vgetcpu_mode = VGETCPU_RDTSCP;
+        else
+                vgetcpu_mode = VGETCPU_LSL;
+
         if (vxtime.hpet_address && notsc) {
                 timetype = hpet_use_timer ? "HPET" : "PIT/HPET";
                 if (hpet_use_timer)