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, 2 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
index 6251a4b10be7..c27caac47ad1 100644
--- a/arch/powerpc/include/asm/hvcall.h
+++ b/arch/powerpc/include/asm/hvcall.h
@@ -274,6 +274,8 @@ struct hcall_stats {
         unsigned long   num_calls;      /* number of calls (on this CPU) */
         unsigned long   tb_total;       /* total wall time (mftb) of calls. */
         unsigned long   purr_total;     /* total cpu time (PURR) of calls. */
+        unsigned long   tb_start;
+        unsigned long   purr_start;
 };
 #define HCALL_STAT_ARRAY_SIZE   ((MAX_HCALL_OPCODE >> 2) + 1)