[tip:perf/core] perf/x86: Add a native_perf_sched_clock_from_tsc( )

[tip-bot for Andi Kleen <tipbot@zytor.com>]

Commit-ID:  a94cab2376cb35f236be14e2833cef63a8762a31
Gitweb:     http://git.kernel.org/tip/a94cab2376cb35f236be14e2833cef63a8762a31
Author:     Andi Kleen <ak@linux.intel.com>
AuthorDate: Sun, 10 May 2015 12:22:39 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 4 Aug 2015 10:16:55 +0200

perf/x86: Add a native_perf_sched_clock_from_tsc()

PEBSv3 has a raw TSC time stamp in its memory buffer that
later needs to to be converted to perf_clock.

Add a native_sched_clock_from_tsc() that works the same
as native_sched_clock(), but starts with an already given
TSC value.

Paravirt is ignored, it will just get the native clock.
But there isn't a para virtualized PEBS anyway.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/1431285767-27027-2-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/tsc.h | 1 +
 arch/x86/kernel/tsc.c      | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 94605c0..aad56eb 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -51,6 +51,7 @@ extern int unsynchronized_tsc(void);
 extern int check_tsc_unstable(void);
 extern int check_tsc_disabled(void);
 extern unsigned long native_calibrate_tsc(void);
+extern unsigned long long native_sched_clock_from_tsc(u64 tsc);
 
 extern int tsc_clocksource_reliable;
 
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 7437b41..88e9a38 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -296,6 +296,14 @@ u64 native_sched_clock(void)
 	return cycles_2_ns(tsc_now);
 }
 
+/*
+ * Generate a sched_clock if you already have a TSC value.
+ */
+u64 native_sched_clock_from_tsc(u64 tsc)
+{
+	return cycles_2_ns(tsc);
+}
+
 /* We need to define a real function for sched_clock, to override the
    weak default version */
 #ifdef CONFIG_PARAVIRT