Patch "powerpc/powernv: Fix opal_exit tracepoint opcode" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

powerpc/powernv: Fix opal_exit tracepoint opcode

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
powerpc-powernv-fix-opal_exit-tracepoint-opcode.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Michael Ellerman <[email protected]>
Date: Tue, 7 Feb 2017 21:01:01 +1100
Subject: powerpc/powernv: Fix opal_exit tracepoint opcode

From: Michael Ellerman <[email protected]>

commit a7e0fb6c2029a780444d09560f739e020d54fe4d upstream.

Currently the opal_exit tracepoint usually shows the opcode as 0:

  <idle>-0     [047] d.h.   635.654292: opal_entry: opcode=63
  <idle>-0     [047] d.h.   635.654296: opal_exit: opcode=0 retval=0
  kopald-1209  [019] d...   636.420943: opal_entry: opcode=10
  kopald-1209  [019] d...   636.420959: opal_exit: opcode=0 retval=0

This is because we incorrectly load the opcode into r0 before calling __trace_opal_exit(), whereas it expects the opcode in r3 (first function parameter). In fact we are leaving the retval in r3, so opcode and retval will always show the same value.

Instead load the opcode into r3, resulting in:

  <idle>-0     [040] d.h.   636.618625: opal_entry: opcode=63
  <idle>-0     [040] d.h.   636.618627: opal_exit: opcode=63 retval=0

---
 arch/powerpc/platforms/powernv/opal-wrappers.S |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -148,7 +148,7 @@ opal_tracepoint_entry:
 opal_tracepoint_return:
 	std	r3,STK_REG(R31)(r1)
 	mr	r4,r3
-	ld	r0,STK_REG(R23)(r1)
+	ld	r3,STK_REG(R23)(r1)
 	bl	__trace_opal_exit
 	ld	r3,STK_REG(R31)(r1)
 	addi	r1,r1,STACKFRAMESIZE

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/powerpc-powernv-fix-opal_exit-tracepoint-opcode.patch