x86, ptrace: support for branch trace store(BTS)

Resend using different mail client

Changes to the last version:
- split implementation into two layers: ds/bts and ptrace
- renamed TIF's
- save/restore ds save area msr in __switch_to_xtra()
- make block-stepping only look at BTF bit

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/setup_64.c b/arch/x86/kernel/setup_64.c
index ce4d6b5..f2b131e 100644
--- a/arch/x86/kernel/setup_64.c
+++ b/arch/x86/kernel/setup_64.c
@@ -60,6 +60,7 @@
 #include <asm/dmi.h>
 #include <asm/cacheflush.h>
 #include <asm/mce.h>
+#include <asm/ds.h>
 
 /*
  * Machine setup..
@@ -823,6 +824,10 @@
 			set_cpu_cap(c, X86_FEATURE_PEBS);
 	}
 
+
+	if (cpu_has_bts)
+		ds_init_intel(c);
+
 	n = c->extended_cpuid_level;
 	if (n >= 0x80000008) {
 		unsigned eax = cpuid_eax(0x80000008);