powerpc/64s/exception: machine check restructure to reuse common macros

Follow the pattern of sreset and HMI handlers more closely: use
EXCEPTION_PROLOG_COMMON_1 rather than open-coding it, and run the
handler at the relocated location.

This helps later simplification and code sharing.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190802105709.27696-12-npiggin@gmail.com

arch/powerpc/kernel/exceptions-64s.S

@@ -934,17 +934,23 @@ EXC_COMMON_BEGIN(system_reset_common)
 
 EXC_REAL_BEGIN(machine_check, 0x200, 0x100)
 	EXCEPTION_PROLOG_0 PACA_EXMC
-	b	machine_check_common_early
+	EXCEPTION_PROLOG_1 EXC_STD, PACA_EXMC, 0, 0x200, 1, 1, 0
+	mfctr	r10			/* save ctr, even for !RELOCATABLE */
+	BRANCH_TO_C000(r11, machine_check_early_common)
+	/*
+	 * MSR_RI is not enabled, because PACA_EXMC is being used, so a
+	 * nested machine check corrupts it. machine_check_common enables
+	 * MSR_RI.
+	 */
 EXC_REAL_END(machine_check, 0x200, 0x100)
 EXC_VIRT_NONE(0x4200, 0x100)
-TRAMP_REAL_BEGIN(machine_check_common_early)
-	EXCEPTION_PROLOG_1 EXC_STD, PACA_EXMC, 0, 0x200, 0, 0, 0
+
+EXC_COMMON_BEGIN(machine_check_early_common)
+	mtctr	r10			/* Restore ctr */
+	mfspr	r11,SPRN_SRR0
+	mfspr	r12,SPRN_SRR1
+
 	/*
-	 * Register contents:
-	 * R13		= PACA
-	 * R9		= CR
-	 * Original R9 to R13 is saved on PACA_EXMC
-	 *
 	 * Switch to mc_emergency stack and handle re-entrancy (we limit
 	 * the nested MCE upto level 4 to avoid stack overflow).
 	 * Save MCE registers srr1, srr0, dar and dsisr and then set ME=1
@@ -965,32 +971,30 @@ TRAMP_REAL_BEGIN(machine_check_common_early)
 	 * the machine check is handled then the idle wakeup code is called
 	 * to restore state.
 	 */
-	mr	r11,r1			/* Save r1 */
 	lhz	r10,PACA_IN_MCE(r13)
 	cmpwi	r10,0			/* Are we in nested machine check */
-	bne	0f			/* Yes, we are. */
-	/* First machine check entry */
-	ld	r1,PACAMCEMERGSP(r13)	/* Use MC emergency stack */
-0:	subi	r1,r1,INT_FRAME_SIZE	/* alloc stack frame */
+	cmpwi	cr1,r10,MAX_MCE_DEPTH	/* Are we at maximum nesting */
 	addi	r10,r10,1		/* increment paca->in_mce */
 	sth	r10,PACA_IN_MCE(r13)
+
+	mr	r10,r1			/* Save r1 */
+	bne	1f
+	/* First machine check entry */
+	ld	r1,PACAMCEMERGSP(r13)	/* Use MC emergency stack */
+1:	subi	r1,r1,INT_FRAME_SIZE	/* alloc stack frame */
 	/* Limit nested MCE to level 4 to avoid stack overflow */
-	cmpwi	r10,MAX_MCE_DEPTH
-	bgt	2f			/* Check if we hit limit of 4 */
-	std	r11,GPR1(r1)		/* Save r1 on the stack. */
-	std	r11,0(r1)		/* make stack chain pointer */
-	mfspr	r11,SPRN_SRR0		/* Save SRR0 */
-	std	r11,_NIP(r1)
-	mfspr	r11,SPRN_SRR1		/* Save SRR1 */
-	std	r11,_MSR(r1)
-	mfspr	r11,SPRN_DAR		/* Save DAR */
-	std	r11,_DAR(r1)
-	mfspr	r11,SPRN_DSISR		/* Save DSISR */
-	std	r11,_DSISR(r1)
-	std	r9,_CCR(r1)		/* Save CR in stackframe */
+	bge	cr1,2f			/* Check if we hit limit of 4 */
+
+	EXCEPTION_PROLOG_COMMON_1()
 	/* We don't touch AMR here, we never go to virtual mode */
-	/* Save r9 through r13 from EXMC save area to stack frame. */
 	EXCEPTION_PROLOG_COMMON_2(PACA_EXMC)
+	EXCEPTION_PROLOG_COMMON_3(0x200)
+
+	ld	r3,PACA_EXMC+EX_DAR(r13)
+	lwz	r4,PACA_EXMC+EX_DSISR(r13)
+	std	r3,_DAR(r1)
+	std	r4,_DSISR(r1)
+
 	mfmsr	r11			/* get MSR value */
 BEGIN_FTR_SECTION
 	ori	r11,r11,MSR_ME		/* turn on ME bit */
@@ -1016,8 +1020,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
 
 #ifdef CONFIG_PPC_PSERIES
 TRAMP_REAL_BEGIN(machine_check_fwnmi)
+	/* See comment at machine_check exception, don't turn on RI */
 	EXCEPTION_PROLOG_0 PACA_EXMC
-	b	machine_check_common_early
+	EXCEPTION_PROLOG_1 EXC_STD, PACA_EXMC, 0, 0x200, 1, 1, 0
+	mfctr	r10		/* save ctr */
+	BRANCH_TO_C000(r11, machine_check_early_common)
 #endif
 
 TRAMP_KVM_SKIP(PACA_EXMC, 0x200)
@@ -1088,8 +1095,6 @@ EXC_COMMON_BEGIN(machine_check_idle_common)
 	 * ME=1, MMU (IR=0 and DR=0) off and using MC emergency stack.
 	 */
 EXC_COMMON_BEGIN(machine_check_handle_early)
-	std	r0,GPR0(r1)	/* Save r0 */
-	EXCEPTION_PROLOG_COMMON_3(0x200)
 	bl	save_nvgprs
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	machine_check_early
@@ -1180,14 +1185,10 @@ BEGIN_FTR_SECTION
 	mtspr	SPRN_CFAR,r10
 END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
 	MACHINE_CHECK_HANDLER_WINDUP
+	/* See comment at machine_check exception, don't turn on RI */
 	EXCEPTION_PROLOG_0 PACA_EXMC
 	EXCEPTION_PROLOG_1 EXC_STD, PACA_EXMC, 1, 0x200, 1, 1, 0
 	EXCEPTION_PROLOG_2_REAL machine_check_common, EXC_STD, 0
-	/*
-	 * MSR_RI is not enabled, because PACA_EXMC is being used, so a
-	 * nested machine check corrupts it. machine_check_common enables
-	 * MSR_RI.
-	 */
 
 EXC_COMMON_BEGIN(unrecover_mce)
 	/* Invoke machine_check_exception to print MCE event and panic. */