x86, tracing, perf: Add trace point for MSR accesses

For debugging low level code interacting with the CPU it is often
useful to trace the MSR read/writes. This gives a concise summary of
PMU and other operations.

perf has an ad-hoc way to do this using trace_printk, but it's
somewhat limited (and also now spews ugly boot messages when enabled)

Instead define real trace points for all MSR accesses.

This adds three new trace points: read_msr and write_msr and rdpmc.

They also report if the access faulted (if *_safe is used)

This allows filtering and triggering on specific MSR values, which
allows various more advanced debugging techniques.

All the values are well defined in the CPU documentation.

The trace can be post processed with
Documentation/trace/postprocess/decode_msr.py to add symbolic MSR
names to the trace.

I only added it to native MSR accesses in C, not paravirtualized or in
entry*.S (which is not too interesting)

Originally the patch kit moved the MSRs out of line.  This uses an
alternative approach recommended by Steven Rostedt of only moving the
trace calls out of line, but open coding the access to the jump label.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1449018060-1742-3-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 57 insertions, 0 deletions

diff --git a/arch/x86/include/asm/msr-trace.h b/arch/x86/include/asm/msr-trace.h
new file mode 100644
index 000000000000..7567225747d8
--- /dev/null
+++ b/arch/x86/include/asm/msr-trace.h
@@ -0,0 +1,57 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM msr
+
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE msr-trace
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH asm/
+
+#if !defined(_TRACE_MSR_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_MSR_H
+
+#include <linux/tracepoint.h>
+
+/*
+ * Tracing for x86 model specific registers. Directly maps to the
+ * RDMSR/WRMSR instructions.
+ */
+
+DECLARE_EVENT_CLASS(msr_trace_class,
+	    TP_PROTO(unsigned msr, u64 val, int failed),
+	    TP_ARGS(msr, val, failed),
+	    TP_STRUCT__entry(
+		    __field(	unsigned,	msr )
+		    __field(    u64,		val )
+		    __field(    int,		failed )
+	    ),
+	    TP_fast_assign(
+		    __entry->msr = msr;
+		    __entry->val = val;
+		    __entry->failed = failed;
+	    ),
+	    TP_printk("%x, value %llx%s",
+		      __entry->msr,
+		      __entry->val,
+		      __entry->failed ? " #GP" : "")
+);
+
+DEFINE_EVENT(msr_trace_class, read_msr,
+	     TP_PROTO(unsigned msr, u64 val, int failed),
+	     TP_ARGS(msr, val, failed)
+);
+
+DEFINE_EVENT(msr_trace_class, write_msr,
+	     TP_PROTO(unsigned msr, u64 val, int failed),
+	     TP_ARGS(msr, val, failed)
+);
+
+DEFINE_EVENT(msr_trace_class, rdpmc,
+	     TP_PROTO(unsigned msr, u64 val, int failed),
+	     TP_ARGS(msr, val, failed)
+);
+
+#endif /* _TRACE_MSR_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>