Patchwork [RFC,1/9] powerpc: Split the common exception prolog logic into two section.

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Submitter Mahesh Salgaonkar
Date Aug. 7, 2013, 9:38 a.m.
Message ID <20130807093806.5389.41596.stgit@mars.in.ibm.com>
Download mbox | patch
Permalink /patch/265440/
State Changes Requested
Headers show

Comments

Mahesh Salgaonkar - Aug. 7, 2013, 9:38 a.m.
From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>

This patch splits the common exception prolog logic into two parts to
facilitate reuse of existing code in the next patch. The second part will
be reused in the machine check exception routine in the next patch.

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

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/exception-64s.h |   67 ++++++++++++++++--------------
 1 file changed, 35 insertions(+), 32 deletions(-)
Anshuman Khandual - Aug. 8, 2013, 4:10 a.m.
On 08/07/2013 03:08 PM, Mahesh J Salgaonkar wrote:
> From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
> 
> This patch splits the common exception prolog logic into two parts to
> facilitate reuse of existing code in the next patch. The second part will
> be reused in the machine check exception routine in the next patch.
> 

Please avoid describing the functionality as a requirement for upcoming
sibling patches. Justification to split the code should be generic functional
or code organizational requirement. We should avoid the word "next patch" in
the commit message, as it would be confusing when you read it later point of
time. The commit message should be self sufficient pertaining to the exact
code change set in consideration.
Benjamin Herrenschmidt - Aug. 8, 2013, 4:16 a.m.
On Thu, 2013-08-08 at 09:40 +0530, Anshuman Khandual wrote:
> On 08/07/2013 03:08 PM, Mahesh J Salgaonkar wrote:
> > From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
> > 
> > This patch splits the common exception prolog logic into two parts to
> > facilitate reuse of existing code in the next patch. The second part will
> > be reused in the machine check exception routine in the next patch.
> > 
> 
> Please avoid describing the functionality as a requirement for upcoming
> sibling patches. Justification to split the code should be generic functional
> or code organizational requirement. We should avoid the word "next patch" in
> the commit message, as it would be confusing when you read it later point of
> time. The commit message should be self sufficient pertaining to the exact
> code change set in consideration.

Ugh ?

It's absolutely common practice to have a patch doing such a split
*specifically* for the purpose of subsequent patches....

In fact it's even *recommended* to separate the split from the
subsequent code change as the code split patch should be a nop, and it
makes the subsequent patch a lot easier to review.

Ben.

Patch

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 07ca627..2386d40 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -248,6 +248,40 @@  do_kvm_##n:								\
 
 #define NOTEST(n)
 
+#define EXCEPTION_PROLOG_COMMON_2(n, area)				   \
+	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	r9,area+EX_R9(r13);	/* move r9, r10 to stackframe	*/ \
+	ld	r10,area+EX_R10(r13);					   \
+	std	r9,GPR9(r1);						   \
+	std	r10,GPR10(r1);						   \
+	ld	r9,area+EX_R11(r13);	/* move r11 - r13 to stackframe	*/ \
+	ld	r10,area+EX_R12(r13);					   \
+	ld	r11,area+EX_R13(r13);					   \
+	std	r9,GPR11(r1);						   \
+	std	r10,GPR12(r1);						   \
+	std	r11,GPR13(r1);						   \
+	BEGIN_FTR_SECTION_NESTED(66);					   \
+	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	*/ \
+	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);				   \
+	mfspr	r11,SPRN_XER;		/* save XER in stackframe	*/ \
+	std	r10,SOFTE(r1);						   \
+	std	r11,_XER(r1);						   \
+	li	r9,(n)+1;						   \
+	std	r9,_TRAP(r1);		/* set trap number		*/ \
+	li	r10,0;							   \
+	ld	r11,exception_marker@toc(r2);				   \
+	std	r10,RESULT(r1);		/* clear regs->result		*/ \
+	std	r11,STACK_FRAME_OVERHEAD-16(r1); /* mark the frame	*/
+
 /*
  * The common exception prolog is used for all except a few exceptions
  * such as a segment miss on a kernel address.  We have to be prepared
@@ -281,38 +315,7 @@  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	*/ \
-	ld	r9,area+EX_R9(r13);	/* move r9, r10 to stackframe	*/ \
-	ld	r10,area+EX_R10(r13);					   \
-	std	r9,GPR9(r1);						   \
-	std	r10,GPR10(r1);						   \
-	ld	r9,area+EX_R11(r13);	/* move r11 - r13 to stackframe	*/ \
-	ld	r10,area+EX_R12(r13);					   \
-	ld	r11,area+EX_R13(r13);					   \
-	std	r9,GPR11(r1);						   \
-	std	r10,GPR12(r1);						   \
-	std	r11,GPR13(r1);						   \
-	BEGIN_FTR_SECTION_NESTED(66);					   \
-	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	*/ \
-	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);				   \
-	mfspr	r11,SPRN_XER;		/* save XER in stackframe	*/ \
-	std	r10,SOFTE(r1);						   \
-	std	r11,_XER(r1);						   \
-	li	r9,(n)+1;						   \
-	std	r9,_TRAP(r1);		/* set trap number		*/ \
-	li	r10,0;							   \
-	ld	r11,exception_marker@toc(r2);				   \
-	std	r10,RESULT(r1);		/* clear regs->result		*/ \
-	std	r11,STACK_FRAME_OVERHEAD-16(r1); /* mark the frame	*/ \
+4:	EXCEPTION_PROLOG_COMMON_2(n, area)				   \
 	ACCOUNT_STOLEN_TIME
 
 /*