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, 37 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/pseries/hvCall_inst.c b/arch/powerpc/platforms/pseries/hvCall_inst.c
index 3631a4f277eb..e44e1035f133 100644
--- a/arch/powerpc/platforms/pseries/hvCall_inst.c
+++ b/arch/powerpc/platforms/pseries/hvCall_inst.c
@@ -26,6 +26,7 @@
 #include <asm/hvcall.h>
 #include <asm/firmware.h>
 #include <asm/cputable.h>
+#include <asm/trace.h>
 
 DEFINE_PER_CPU(struct hcall_stats[HCALL_STAT_ARRAY_SIZE], hcall_stats);
 
@@ -100,6 +101,34 @@ static const struct file_operations hcall_inst_seq_fops = {
 #define HCALL_ROOT_DIR          "hcall_inst"
 #define CPU_NAME_BUF_SIZE       32
 
+
+static void probe_hcall_entry(unsigned long opcode)
+{
+        struct hcall_stats *h;
+
+        if (opcode > MAX_HCALL_OPCODE)
+                return;
+
+        h = &get_cpu_var(hcall_stats)[opcode / 4];
+        h->tb_start = mftb();
+        h->purr_start = mfspr(SPRN_PURR);
+}
+
+static void probe_hcall_exit(unsigned long opcode, unsigned long retval)
+{
+        struct hcall_stats *h;
+
+        if (opcode > MAX_HCALL_OPCODE)
+                return;
+
+        h = &__get_cpu_var(hcall_stats)[opcode / 4];
+        h->num_calls++;
+        h->tb_total = mftb() - h->tb_start;
+        h->purr_total = mfspr(SPRN_PURR) - h->purr_start;
+
+        put_cpu_var(hcall_stats);
+}
+
 static int __init hcall_inst_init(void)
 {
         struct dentry *hcall_root;
@@ -110,6 +139,14 @@ static int __init hcall_inst_init(void)
         if (!firmware_has_feature(FW_FEATURE_LPAR))
                 return 0;
 
+        if (register_trace_hcall_entry(probe_hcall_entry))
+                return -EINVAL;
+
+        if (register_trace_hcall_exit(probe_hcall_exit)) {
+                unregister_trace_hcall_entry(probe_hcall_entry);
+                return -EINVAL;
+        }
+
         hcall_root = debugfs_create_dir(HCALL_ROOT_DIR, NULL);
         if (!hcall_root)
                 return -ENOMEM;