powerpc/64s/exception: Remove confusing IEARLY option

Replace IEARLY=1 and IEARLY=2 with IBRANCH_COMMON, which controls if
the entry code branches to a common handler; and IREALMODE_COMMON,
which controls whether the common handler should remain in real mode.

These special cases no longer avoid loading the SRR registers, there
is no point as most of them load the registers immediately anyway.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200225173541.1549955-14-npiggin@gmail.com

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

@@ -174,7 +174,8 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
 #define IDAR		.L_IDAR_\name\()
 #define IDSISR		.L_IDSISR_\name\()
 #define ISET_RI		.L_ISET_RI_\name\()
-#define IEARLY		.L_IEARLY_\name\()
+#define IBRANCH_TO_COMMON	.L_IBRANCH_TO_COMMON_\name\()
+#define IREALMODE_COMMON	.L_IREALMODE_COMMON_\name\()
 #define IMASK		.L_IMASK_\name\()
 #define IKVM_SKIP	.L_IKVM_SKIP_\name\()
 #define IKVM_REAL	.L_IKVM_REAL_\name\()
@@ -218,8 +219,15 @@ do_define_int n
 	.ifndef ISET_RI
 		ISET_RI=1
 	.endif
-	.ifndef IEARLY
-		IEARLY=0
+	.ifndef IBRANCH_TO_COMMON
+		IBRANCH_TO_COMMON=1
+	.endif
+	.ifndef IREALMODE_COMMON
+		IREALMODE_COMMON=0
+	.else
+		.if ! IBRANCH_TO_COMMON
+			.error "IREALMODE_COMMON=1 but IBRANCH_TO_COMMON=0"
+		.endif
 	.endif
 	.ifndef IMASK
 		IMASK=0
@@ -353,6 +361,11 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,948)
  */
 
 .macro GEN_BRANCH_TO_COMMON name, virt
+	.if IREALMODE_COMMON
+	LOAD_HANDLER(r10, \name\()_common)
+	mtctr	r10
+	bctr
+	.else
 	.if \virt
 #ifndef CONFIG_RELOCATABLE
 	b	\name\()_common_virt
@@ -366,6 +379,7 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,948)
 	mtctr	r10
 	bctr
 	.endif
+	.endif
 .endm
 
 .macro GEN_INT_ENTRY name, virt, ool=0
@@ -421,11 +435,6 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,948)
 	stw	r10,IAREA+EX_DSISR(r13)
 	.endif
 
-	.if IEARLY == 2
-	/* nothing more */
-	.elseif IEARLY
-	BRANCH_TO_C000(r11, \name\()_common)
-	.else
 	.if IHSRR == EXC_HV_OR_STD
 	BEGIN_FTR_SECTION
 	mfspr	r11,SPRN_HSRR0		/* save HSRR0 */
@@ -441,6 +450,8 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,948)
 	mfspr	r11,SPRN_SRR0		/* save SRR0 */
 	mfspr	r12,SPRN_SRR1		/* and SRR1 */
 	.endif
+
+	.if IBRANCH_TO_COMMON
 	GEN_BRANCH_TO_COMMON \name \virt
 	.endif
 
@@ -940,6 +951,7 @@ INT_DEFINE_BEGIN(machine_check_early)
 	IVEC=0x200
 	IAREA=PACA_EXMC
 	IVIRT=0 /* no virt entry point */
+	IREALMODE_COMMON=1
 	/*
 	 * MSR_RI is not enabled, because PACA_EXMC is being used, so a
 	 * nested machine check corrupts it. machine_check_common enables
@@ -947,7 +959,6 @@ INT_DEFINE_BEGIN(machine_check_early)
 	 */
 	ISET_RI=0
 	ISTACK=0
-	IEARLY=1
 	IDAR=1
 	IDSISR=1
 	IRECONCILE=0
@@ -987,9 +998,6 @@ TRAMP_REAL_BEGIN(machine_check_fwnmi)
 	EXCEPTION_RESTORE_REGS EXC_STD
 
 EXC_COMMON_BEGIN(machine_check_early_common)
-	mfspr	r11,SPRN_SRR0
-	mfspr	r12,SPRN_SRR1
-
 	__GEN_REALMODE_COMMON_ENTRY machine_check_early
 
 	/*
@@ -1825,7 +1833,7 @@ EXC_COMMON_BEGIN(emulation_assist_common)
 INT_DEFINE_BEGIN(hmi_exception_early)
 	IVEC=0xe60
 	IHSRR=EXC_HV
-	IEARLY=1
+	IREALMODE_COMMON=1
 	ISTACK=0
 	IRECONCILE=0
 	IKUAP=0 /* We don't touch AMR here, we never go to virtual mode */
@@ -1845,9 +1853,6 @@ EXC_REAL_END(hmi_exception, 0xe60, 0x20)
 EXC_VIRT_NONE(0x4e60, 0x20)
 
 EXC_COMMON_BEGIN(hmi_exception_early_common)
-	mfspr	r11,SPRN_HSRR0		/* Save HSRR0 */
-	mfspr	r12,SPRN_HSRR1		/* Save HSRR1 */
-
 	__GEN_REALMODE_COMMON_ENTRY hmi_exception_early
 
 	mr	r10,r1			/* Save r1 */
@@ -2175,29 +2180,23 @@ EXC_VIRT_NONE(0x5400, 0x100)
 INT_DEFINE_BEGIN(denorm_exception)
 	IVEC=0x1500
 	IHSRR=EXC_HV
-	IEARLY=2
+	IBRANCH_TO_COMMON=0
 	IKVM_REAL=1
 INT_DEFINE_END(denorm_exception)
 
 EXC_REAL_BEGIN(denorm_exception, 0x1500, 0x100)
 	GEN_INT_ENTRY denorm_exception, virt=0
 #ifdef CONFIG_PPC_DENORMALISATION
-	mfspr	r10,SPRN_HSRR1
-	andis.	r10,r10,(HSRR1_DENORM)@h /* denorm? */
+	andis.	r10,r12,(HSRR1_DENORM)@h /* denorm? */
 	bne+	denorm_assist
 #endif
-	mfspr	r11,SPRN_HSRR0
-	mfspr	r12,SPRN_HSRR1
 	GEN_BRANCH_TO_COMMON denorm_exception, virt=0
 EXC_REAL_END(denorm_exception, 0x1500, 0x100)
 #ifdef CONFIG_PPC_DENORMALISATION
 EXC_VIRT_BEGIN(denorm_exception, 0x5500, 0x100)
 	GEN_INT_ENTRY denorm_exception, virt=1
-	mfspr	r10,SPRN_HSRR1
-	andis.	r10,r10,(HSRR1_DENORM)@h /* denorm? */
+	andis.	r10,r12,(HSRR1_DENORM)@h /* denorm? */
 	bne+	denorm_assist
-	mfspr	r11,SPRN_HSRR0
-	mfspr	r12,SPRN_HSRR1
 	GEN_BRANCH_TO_COMMON denorm_exception, virt=1
 EXC_VIRT_END(denorm_exception, 0x5500, 0x100)
 #else