powerpc/pseries: hcall_exit tracepoint retval should be signed

The hcall_exit() tracepoint has retval defined as unsigned long. That
leads to humours results like:

  bash-3686  [009] d..2   854.134094: hcall_entry: opcode=24
  bash-3686  [009] d..2   854.134095: hcall_exit: opcode=24 retval=18446744073709551609

It's normal for some hcalls to return negative values, displaying them
as unsigned isn't very helpful. So change it to signed.

  bash-3711  [001] d..2   471.691008: hcall_entry: opcode=24
  bash-3711  [001] d..2   471.691008: hcall_exit: opcode=24 retval=-7

Which can be more easily compared to H_NOT_FOUND in hvcall.h

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Tested-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>

arch/powerpc/include/asm/asm-prototypes.h

@@ -36,8 +36,7 @@ void kexec_copy_flush(struct kimage *image);
 /* pseries hcall tracing */
 extern struct static_key hcall_tracepoint_key;
 void __trace_hcall_entry(unsigned long opcode, unsigned long *args);
-void __trace_hcall_exit(long opcode, unsigned long retval,
-			unsigned long *retbuf);
+void __trace_hcall_exit(long opcode, long retval, unsigned long *retbuf);
 /* OPAL tracing */
 #ifdef HAVE_JUMP_LABEL
 extern struct static_key opal_tracepoint_key;

arch/powerpc/include/asm/trace.h

@@ -81,8 +81,7 @@ TRACE_EVENT_FN_COND(hcall_entry,
 
 TRACE_EVENT_FN_COND(hcall_exit,
 
-	TP_PROTO(unsigned long opcode, unsigned long retval,
-		unsigned long *retbuf),
+	TP_PROTO(unsigned long opcode, long retval, unsigned long *retbuf),
 
 	TP_ARGS(opcode, retval, retbuf),
 
@@ -90,7 +89,7 @@ TRACE_EVENT_FN_COND(hcall_exit,
 
 	TP_STRUCT__entry(
 		__field(unsigned long, opcode)
-		__field(unsigned long, retval)
+		__field(long, retval)
 	),
 
 	TP_fast_assign(
@@ -98,7 +97,7 @@ TRACE_EVENT_FN_COND(hcall_exit,
 		__entry->retval = retval;
 	),
 
-	TP_printk("opcode=%lu retval=%lu", __entry->opcode, __entry->retval),
+	TP_printk("opcode=%lu retval=%ld", __entry->opcode, __entry->retval),
 
 	hcall_tracepoint_regfunc, hcall_tracepoint_unregfunc
 );

arch/powerpc/platforms/pseries/hvCall_inst.c

@@ -125,7 +125,7 @@ static void probe_hcall_entry(void *ignored, unsigned long opcode, unsigned long
 	h->purr_start = mfspr(SPRN_PURR);
 }
 
-static void probe_hcall_exit(void *ignored, unsigned long opcode, unsigned long retval,
+static void probe_hcall_exit(void *ignored, unsigned long opcode, long retval,
 			     unsigned long *retbuf)
 {
 	struct hcall_stats *h;

arch/powerpc/platforms/pseries/lpar.c

@@ -902,8 +902,7 @@ out:
 	local_irq_restore(flags);
 }
 
-void __trace_hcall_exit(long opcode, unsigned long retval,
-			unsigned long *retbuf)
+void __trace_hcall_exit(long opcode, long retval, unsigned long *retbuf)
 {
 	unsigned long flags;
 	unsigned int *depth;