linux-kernel - [for-next][PATCH 4/4] x86: Use tracepoint_enabled() for msr tracepoints instead of open coding it

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Date:   Mon, 28 Sep 2020 21:12:00 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [for-next][PATCH 4/4] x86: Use tracepoint_enabled() for msr tracepoints instead of open
 coding it

From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>

7f47d8cc039f ("x86, tracing, perf: Add trace point for MSR accesses") added
tracing of msr read and write, but because of complexity in having
tracepoints in headers, and even more so for a core header like msr.h, not
to mention the bloat a tracepoint adds to inline functions, a helper
function is needed to be called from the header.

Use the new tracepoint_enabled() macro in tracepoint-defs.h to test if the
tracepoint is active before calling the helper function, instead of open
coding the same logic, which requires knowing the internals of a tracepoint.

Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 arch/x86/include/asm/msr.h | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 86f20d520a07..0b4920a7238e 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -60,22 +60,20 @@ struct saved_msrs {
 #define EAX_EDX_RET(val, low, high)	"=A" (val)
 #endif
 
-#ifdef CONFIG_TRACEPOINTS
 /*
  * Be very careful with includes. This header is prone to include loops.
  */
 #include <asm/atomic.h>
 #include <linux/tracepoint-defs.h>
 
-extern struct tracepoint __tracepoint_read_msr;
-extern struct tracepoint __tracepoint_write_msr;
-extern struct tracepoint __tracepoint_rdpmc;
-#define msr_tracepoint_active(t) static_key_false(&(t).key)
+#ifdef CONFIG_TRACEPOINTS
+DECLARE_TRACEPOINT(read_msr);
+DECLARE_TRACEPOINT(write_msr);
+DECLARE_TRACEPOINT(rdpmc);
 extern void do_trace_write_msr(unsigned int msr, u64 val, int failed);
 extern void do_trace_read_msr(unsigned int msr, u64 val, int failed);
 extern void do_trace_rdpmc(unsigned int msr, u64 val, int failed);
 #else
-#define msr_tracepoint_active(t) false
 static inline void do_trace_write_msr(unsigned int msr, u64 val, int failed) {}
 static inline void do_trace_read_msr(unsigned int msr, u64 val, int failed) {}
 static inline void do_trace_rdpmc(unsigned int msr, u64 val, int failed) {}
@@ -128,7 +126,7 @@ static inline unsigned long long native_read_msr(unsigned int msr)
 
 	val = __rdmsr(msr);
 
-	if (msr_tracepoint_active(__tracepoint_read_msr))
+	if (tracepoint_enabled(read_msr))
 		do_trace_read_msr(msr, val, 0);
 
 	return val;
@@ -150,7 +148,7 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr,
 		     _ASM_EXTABLE(2b, 3b)
 		     : [err] "=r" (*err), EAX_EDX_RET(val, low, high)
 		     : "c" (msr), [fault] "i" (-EIO));
-	if (msr_tracepoint_active(__tracepoint_read_msr))
+	if (tracepoint_enabled(read_msr))
 		do_trace_read_msr(msr, EAX_EDX_VAL(val, low, high), *err);
 	return EAX_EDX_VAL(val, low, high);
 }
@@ -161,7 +159,7 @@ native_write_msr(unsigned int msr, u32 low, u32 high)
 {
 	__wrmsr(msr, low, high);
 
-	if (msr_tracepoint_active(__tracepoint_write_msr))
+	if (tracepoint_enabled(write_msr))
 		do_trace_write_msr(msr, ((u64)high << 32 | low), 0);
 }
 
@@ -181,7 +179,7 @@ native_write_msr_safe(unsigned int msr, u32 low, u32 high)
 		     : "c" (msr), "0" (low), "d" (high),
 		       [fault] "i" (-EIO)
 		     : "memory");
-	if (msr_tracepoint_active(__tracepoint_write_msr))
+	if (tracepoint_enabled(write_msr))
 		do_trace_write_msr(msr, ((u64)high << 32 | low), err);
 	return err;
 }
@@ -248,7 +246,7 @@ static inline unsigned long long native_read_pmc(int counter)
 	DECLARE_ARGS(val, low, high);
 
 	asm volatile("rdpmc" : EAX_EDX_RET(val, low, high) : "c" (counter));
-	if (msr_tracepoint_active(__tracepoint_rdpmc))
+	if (tracepoint_enabled(rdpmc))
 		do_trace_rdpmc(counter, EAX_EDX_VAL(val, low, high), 0);
 	return EAX_EDX_VAL(val, low, high);
 }
-- 
2.28.0