powerpc/pseries: Use jump labels for hcall tracepoints

hcall tracepoints add quite a few instructions to our hcall path:

plpar_hcall:
	mr      r2,r2
	mfcr    r0
	stw     r0,8(r1)
	b       164		<---- start
	ld      r12,0(r2)
	std     r12,32(r1)
	cmpdi   r12,0
	beq     164		<---- end
...

We have an unconditional branch that gets noped out during boot and
a load/compare/branch. We also store the tracepoint value to the
stack for the hcall_exit path to use.

By using jump labels we can simplify this to just a single nop that
gets replaced with a branch when the tracepoint is enabled:

plpar_hcall:
	mr      r2,r2
	mfcr    r0
	stw     r0,8(r1)
	nop			<----
...

If jump labels are not enabled, we fall back to the old method.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/jump_label.h

@@ -10,6 +10,7 @@
  * 2 of the License, or (at your option) any later version.
  */
 
+#ifndef __ASSEMBLY__
 #include <linux/types.h>
 
 #include <asm/feature-fixups.h>
@@ -42,4 +43,12 @@ struct jump_entry {
 	jump_label_t key;
 };
 
+#else
+#define ARCH_STATIC_BRANCH(LABEL, KEY)		\
+1098:	nop;					\
+	.pushsection __jump_table, "aw";	\
+	FTR_ENTRY_LONG 1098b, LABEL, KEY;	\
+	.popsection
+#endif
+
 #endif /* _ASM_POWERPC_JUMP_LABEL_H */