powerpc: tracing: Add hypervisor call tracepoints

Add hcall_entry and hcall_exit tracepoints.  This replaces the inline
assembly HCALL_STATS code and converts it to use the new tracepoints.

To keep the disabled case as quick as possible, we embed a status word
in the TOC so we can get at it with a single load.  By doing so we
keep the overhead at a minimum.  Time taken for a null hcall:

No tracepoint code:	135.79 cycles
Disabled tracepoints:	137.95 cycles

For reference, before this patch enabling HCALL_STATS resulted in a null
hcall of 201.44 cycles!

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 58 insertions, 43 deletions

diff --git a/arch/powerpc/platforms/pseries/hvCall.S b/arch/powerpc/platforms/pseries/hvCall.S
index c1427b3634e..01e95ab18d3 100644
--- a/arch/powerpc/platforms/pseries/hvCall.S
+++ b/arch/powerpc/platforms/pseries/hvCall.S
@@ -14,20 +14,54 @@
 	
 #define STK_PARM(i)     (48 + ((i)-3)*8)
 
-#ifdef CONFIG_HCALL_STATS
+#ifdef CONFIG_TRACEPOINTS
+
+	.section	".toc","aw"
+
+	.globl hcall_tracepoint_refcount
+hcall_tracepoint_refcount:
+	.llong	0
+
+	.section	".text"
+
 /*
  * precall must preserve all registers.  use unused STK_PARM()
- * areas to save snapshots and opcode.
+ * areas to save snapshots and opcode. We branch around this
+ * in early init (eg when populating the MMU hashtable) by using an
+ * unconditional cpu feature.
  */
 #define HCALL_INST_PRECALL					\
-	std	r3,STK_PARM(r3)(r1);	/* save opcode */	\
-	mftb	r0;			/* get timebase and */	\
-	std     r0,STK_PARM(r5)(r1);	/* save for later */	\
 BEGIN_FTR_SECTION;						\
-	mfspr	r0,SPRN_PURR;		/* get PURR and */	\
-	std	r0,STK_PARM(r6)(r1);	/* save for later */	\
-END_FTR_SECTION_IFSET(CPU_FTR_PURR);
-	
+	b	1f;						\
+END_FTR_SECTION(0, 1);						\
+	ld      r12,hcall_tracepoint_refcount@toc(r2);		\
+	cmpdi	r12,0;						\
+	beq+	1f;						\
+	mflr	r0;						\
+	std	r3,STK_PARM(r3)(r1);				\
+	std	r4,STK_PARM(r4)(r1);				\
+	std	r5,STK_PARM(r5)(r1);				\
+	std	r6,STK_PARM(r6)(r1);				\
+	std	r7,STK_PARM(r7)(r1);				\
+	std	r8,STK_PARM(r8)(r1);				\
+	std	r9,STK_PARM(r9)(r1);				\
+	std	r10,STK_PARM(r10)(r1);				\
+	std	r0,16(r1);					\
+	stdu	r1,-STACK_FRAME_OVERHEAD(r1);			\
+	bl	.__trace_hcall_entry;				\
+	addi	r1,r1,STACK_FRAME_OVERHEAD;			\
+	ld	r0,16(r1);					\
+	ld	r3,STK_PARM(r3)(r1);				\
+	ld	r4,STK_PARM(r4)(r1);				\
+	ld	r5,STK_PARM(r5)(r1);				\
+	ld	r6,STK_PARM(r6)(r1);				\
+	ld	r7,STK_PARM(r7)(r1);				\
+	ld	r8,STK_PARM(r8)(r1);				\
+	ld	r9,STK_PARM(r9)(r1);				\
+	ld	r10,STK_PARM(r10)(r1);				\
+	mtlr	r0;						\
+1:
+
 /*
  * postcall is performed immediately before function return which
  * allows liberal use of volatile registers.  We branch around this
@@ -38,40 +72,21 @@ END_FTR_SECTION_IFSET(CPU_FTR_PURR);
 BEGIN_FTR_SECTION;						\
 	b	1f;						\
 END_FTR_SECTION(0, 1);						\
-	ld	r4,STK_PARM(r3)(r1);	/* validate opcode */	\
-	cmpldi	cr7,r4,MAX_HCALL_OPCODE;			\
-	bgt-	cr7,1f;						\
-								\
-	/* get time and PURR snapshots after hcall */		\
-	mftb	r7;			/* timebase after */	\
-BEGIN_FTR_SECTION;						\
-	mfspr	r8,SPRN_PURR;		/* PURR after */	\
-	ld	r6,STK_PARM(r6)(r1);	/* PURR before */	\
-	subf	r6,r6,r8;		/* delta */		\
-END_FTR_SECTION_IFSET(CPU_FTR_PURR);				\
-	ld	r5,STK_PARM(r5)(r1);	/* timebase before */	\
-	subf	r5,r5,r7;		/* time delta */	\
-								\
-	/* calculate address of stat structure r4 = opcode */	\
-	srdi	r4,r4,2;		/* index into array */	\
-	mulli	r4,r4,HCALL_STAT_SIZE;				\
-	LOAD_REG_ADDR(r7, per_cpu__hcall_stats);		\
-	add	r4,r4,r7;					\
-	ld	r7,PACA_DATA_OFFSET(r13); /* per cpu offset */	\
-	add	r4,r4,r7;					\
-								\
-	/* update stats	*/					\
-	ld	r7,HCALL_STAT_CALLS(r4); /* count */		\
-	addi	r7,r7,1;					\
-	std	r7,HCALL_STAT_CALLS(r4);			\
-	ld      r7,HCALL_STAT_TB(r4);	/* timebase */		\
-	add	r7,r7,r5;					\
-	std	r7,HCALL_STAT_TB(r4);				\
-BEGIN_FTR_SECTION;						\
-	ld	r7,HCALL_STAT_PURR(r4);	/* PURR */		\
-	add	r7,r7,r6;					\
-	std	r7,HCALL_STAT_PURR(r4);				\
-END_FTR_SECTION_IFSET(CPU_FTR_PURR);				\
+	ld      r12,hcall_tracepoint_refcount@toc(r2);		\
+	cmpdi	r12,0;						\
+	beq+	1f;						\
+	mflr	r0;						\
+	ld	r6,STK_PARM(r3)(r1);				\
+	std	r3,STK_PARM(r3)(r1);				\
+	mr	r4,r3;						\
+	mr	r3,r6;						\
+	std	r0,16(r1);					\
+	stdu	r1,-STACK_FRAME_OVERHEAD(r1);			\
+	bl	.__trace_hcall_exit;				\
+	addi	r1,r1,STACK_FRAME_OVERHEAD;			\
+	ld	r0,16(r1);					\
+	ld	r3,STK_PARM(r3)(r1);				\
+	mtlr	r0;						\
 1:
 #else
 #define HCALL_INST_PRECALL