[RFC PATCH v4 01/12] powerpc/book3s: Split the common exception prolog logic into two section.

[Mahesh J Salgaonkar]

From: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>

This patch splits the common exception prolog logic into three parts to
facilitate reuse of existing code in the next patch. This patch also
re-arranges few instructions in such a way that the second part now deals
with saving register values from paca save area to stack frame, and
the third part deals with saving current register values to stack frame.

The second and third part will be reused in the machine check exception
routine in the subsequent patch.

Please note that this patch does not introduce or change existing code
logic. Instead it is just a code movement and instruction re-ordering.

Patch Acked-by Paul. But made some minor modification (explained above) to
address Paul's comment in the later patch(3).

Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
Acked-by: Paul Mackerras <paulus at samba.org>
---
 arch/powerpc/include/asm/exception-64s.h |   21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 07ca627..94ab2d2 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -281,9 +281,12 @@ do_kvm_##n:								\
 	beq	4f;			/* if from kernel mode		*/ \
 	ACCOUNT_CPU_USER_ENTRY(r9, r10);				   \
 	SAVE_PPR(area, r9, r10);					   \
-4:	std	r2,GPR2(r1);		/* save r2 in stackframe	*/ \
-	SAVE_4GPRS(3, r1);		/* save r3 - r6 in stackframe	*/ \
-	SAVE_2GPRS(7, r1);		/* save r7, r8 in stackframe	*/ \
+4:	EXCEPTION_PROLOG_COMMON_2(area)					   \
+	EXCEPTION_PROLOG_COMMON_3(n)					   \
+	ACCOUNT_STOLEN_TIME
+
+/* Save original regs values from save area to stack frame. */
+#define EXCEPTION_PROLOG_COMMON_2(area)					   \
 	ld	r9,area+EX_R9(r13);	/* move r9, r10 to stackframe	*/ \
 	ld	r10,area+EX_R10(r13);					   \
 	std	r9,GPR9(r1);						   \
@@ -298,9 +301,14 @@ do_kvm_##n:								\
 	ld	r10,area+EX_CFAR(r13);					   \
 	std	r10,ORIG_GPR3(r1);					   \
 	END_FTR_SECTION_NESTED(CPU_FTR_CFAR, CPU_FTR_CFAR, 66);		   \
-	GET_LR(r9,area);		/* Get LR, later save to stack	*/ \
+	GET_LR(r9,area);		/* Save LR to stack	*/ \
+	std	r9,_LINK(r1);
+
+#define EXCEPTION_PROLOG_COMMON_3(n)					   \
+	std	r2,GPR2(r1);		/* save r2 in stackframe	*/ \
+	SAVE_4GPRS(3, r1);		/* save r3 - r6 in stackframe	*/ \
+	SAVE_2GPRS(7, r1);		/* save r7, r8 in stackframe	*/ \
 	ld	r2,PACATOC(r13);	/* get kernel TOC into r2	*/ \
-	std	r9,_LINK(r1);						   \
 	mfctr	r10;			/* save CTR in stackframe	*/ \
 	std	r10,_CTR(r1);						   \
 	lbz	r10,PACASOFTIRQEN(r13);				   \
@@ -312,8 +320,7 @@ do_kvm_##n:								\
 	li	r10,0;							   \
 	ld	r11,exception_marker at toc(r2);				   \
 	std	r10,RESULT(r1);		/* clear regs->result		*/ \
-	std	r11,STACK_FRAME_OVERHEAD-16(r1); /* mark the frame	*/ \
-	ACCOUNT_STOLEN_TIME
+	std	r11,STACK_FRAME_OVERHEAD-16(r1); /* mark the frame	*/
 
 /*
  * Exception vectors.