[POWERPC] Lazy interrupt disabling for 64-bit machines

This implements a lazy strategy for disabling interrupts.  This means
that local_irq_disable() et al. just clear the 'interrupts are
enabled' flag in the paca.  If an interrupt comes along, the interrupt
entry code notices that interrupts are supposed to be disabled, and
clears the EE bit in SRR1, clears the 'interrupts are hard-enabled'
flag in the paca, and returns.  This means that interrupts only
actually get disabled in the processor when an interrupt comes along.

When interrupts are enabled by local_irq_enable() et al., the code
sets the interrupts-enabled flag in the paca, and then checks whether
interrupts got hard-disabled.  If so, it also sets the EE bit in the
MSR to hard-enable the interrupts.

This has the potential to improve performance, and also makes it
easier to make a kernel that can boot on iSeries and on other 64-bit
machines, since this lazy-disable strategy is very similar to the
soft-disable strategy that iSeries already uses.

This version renames paca->proc_enabled to paca->soft_enabled, and
changes a couple of soft-disables in the kexec code to hard-disables,
which should fix the crash that Michael Ellerman saw.  This doesn't
yet use a reserved CR field for the soft_enabled and hard_enabled
flags.  This applies on top of Stephen Rothwell's patches to make it
possible to build a combined iSeries/other kernel.

Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 77 insertions, 33 deletions

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 645c7f10fb2..c93d9f35a12 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -35,9 +35,7 @@
 #include <asm/thread_info.h>
 #include <asm/firmware.h>
 
-#ifdef CONFIG_PPC_ISERIES
 #define DO_SOFT_DISABLE
-#endif
 
 /*
  * We layout physical memory as follows:
@@ -308,7 +306,9 @@ exception_marker:
 	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		*/ \
@@ -343,6 +343,34 @@ label##_pSeries:					\
 	EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, label##_common)
 
 
+#define MASKABLE_EXCEPTION_PSERIES(n, label)				\
+	. = n;								\
+	.globl label##_pSeries;						\
+label##_pSeries:							\
+	HMT_MEDIUM;							\
+	mtspr	SPRN_SPRG1,r13;		/* save r13 */			\
+	mfspr	r13,SPRN_SPRG3;		/* get paca address into r13 */	\
+	std	r9,PACA_EXGEN+EX_R9(r13);	/* save r9, r10 */	\
+	std	r10,PACA_EXGEN+EX_R10(r13);				\
+	lbz	r10,PACASOFTIRQEN(r13);					\
+	mfcr	r9;							\
+	cmpwi	r10,0;							\
+	beq	masked_interrupt;					\
+	mfspr	r10,SPRN_SPRG1;						\
+	std	r10,PACA_EXGEN+EX_R13(r13);				\
+	std	r11,PACA_EXGEN+EX_R11(r13);				\
+	std	r12,PACA_EXGEN+EX_R12(r13);				\
+	clrrdi	r12,r13,32;		/* get high part of &label */	\
+	mfmsr	r10;							\
+	mfspr	r11,SPRN_SRR0;		/* save SRR0 */			\
+	LOAD_HANDLER(r12,label##_common)				\
+	ori	r10,r10,MSR_IR|MSR_DR|MSR_RI;				\
+	mtspr	SPRN_SRR0,r12;						\
+	mfspr	r12,SPRN_SRR1;		/* and SRR1 */			\
+	mtspr	SPRN_SRR1,r10;						\
+	rfid;								\
+	b	.	/* prevent speculative execution */
+
 #define STD_EXCEPTION_ISERIES(n, label, area)		\
 	.globl label##_iSeries;				\
 label##_iSeries:					\
@@ -358,40 +386,32 @@ label##_iSeries:							\
 	HMT_MEDIUM;							\
 	mtspr	SPRN_SPRG1,r13;		/* save r13 */			\
 	EXCEPTION_PROLOG_ISERIES_1(PACA_EXGEN);				\
-	lbz	r10,PACAPROCENABLED(r13);				\
+	lbz	r10,PACASOFTIRQEN(r13);					\
 	cmpwi	0,r10,0;						\
 	beq-	label##_iSeries_masked;					\
 	EXCEPTION_PROLOG_ISERIES_2;					\
 	b	label##_common;						\
 
-#ifdef DO_SOFT_DISABLE
+#ifdef CONFIG_PPC_ISERIES
 #define DISABLE_INTS				\
-BEGIN_FW_FTR_SECTION;				\
-	lbz	r10,PACAPROCENABLED(r13);	\
 	li	r11,0;				\
-	std	r10,SOFTE(r1);			\
+	stb	r11,PACASOFTIRQEN(r13);		\
+BEGIN_FW_FTR_SECTION;				\
+	stb	r11,PACAHARDIRQEN(r13);		\
+END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES);	\
+BEGIN_FW_FTR_SECTION;				\
 	mfmsr	r10;				\
-	stb	r11,PACAPROCENABLED(r13);	\
 	ori	r10,r10,MSR_EE;			\
 	mtmsrd	r10,1;				\
 END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
 
-#define ENABLE_INTS				\
-BEGIN_FW_FTR_SECTION;				\
-	lbz	r10,PACAPROCENABLED(r13);	\
-	mfmsr	r11;				\
-	std	r10,SOFTE(r1);			\
-	ori	r11,r11,MSR_EE;			\
-END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES);	\
-BEGIN_FW_FTR_SECTION;				\
-	ld	r12,_MSR(r1);			\
-	mfmsr	r11;				\
-	rlwimi	r11,r12,0,MSR_EE;		\
-END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES);	\
-	mtmsrd	r11,1
+#else
+#define DISABLE_INTS				\
+	li	r11,0;				\
+	stb	r11,PACASOFTIRQEN(r13);		\
+	stb	r11,PACAHARDIRQEN(r13)
 
-#else	/* hard enable/disable interrupts */
-#define DISABLE_INTS
+#endif /* CONFIG_PPC_ISERIES */
 
 #define ENABLE_INTS				\
 	ld	r12,_MSR(r1);			\
@@ -399,8 +419,6 @@ END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES);	\
 	rlwimi	r11,r12,0,MSR_EE;		\
 	mtmsrd	r11,1
 
-#endif
-
 #define STD_EXCEPTION_COMMON(trap, label, hdlr)		\
 	.align	7;					\
 	.globl label##_common;				\
@@ -541,11 +559,11 @@ instruction_access_slb_pSeries:
 	mfspr	r12,SPRN_SRR1		/* and SRR1 */
 	b	.slb_miss_realmode	/* Rel. branch works in real mode */
 
-	STD_EXCEPTION_PSERIES(0x500, hardware_interrupt)
+	MASKABLE_EXCEPTION_PSERIES(0x500, hardware_interrupt)
 	STD_EXCEPTION_PSERIES(0x600, alignment)
 	STD_EXCEPTION_PSERIES(0x700, program_check)
 	STD_EXCEPTION_PSERIES(0x800, fp_unavailable)
-	STD_EXCEPTION_PSERIES(0x900, decrementer)
+	MASKABLE_EXCEPTION_PSERIES(0x900, decrementer)
 	STD_EXCEPTION_PSERIES(0xa00, trap_0a)
 	STD_EXCEPTION_PSERIES(0xb00, trap_0b)
 
@@ -597,7 +615,24 @@ system_call_pSeries:
 /*** pSeries interrupt support ***/
 
 	/* moved from 0xf00 */
-	STD_EXCEPTION_PSERIES(., performance_monitor)
+	MASKABLE_EXCEPTION_PSERIES(., performance_monitor)
+
+/*
+ * An interrupt came in while soft-disabled; clear EE in SRR1,
+ * clear paca->hard_enabled and return.
+ */
+masked_interrupt:
+	stb	r10,PACAHARDIRQEN(r13)
+	mtcrf	0x80,r9
+	ld	r9,PACA_EXGEN+EX_R9(r13)
+	mfspr	r10,SPRN_SRR1
+	rldicl	r10,r10,48,1		/* clear MSR_EE */
+	rotldi	r10,r10,16
+	mtspr	SPRN_SRR1,r10
+	ld	r10,PACA_EXGEN+EX_R10(r13)
+	mfspr	r13,SPRN_SPRG1
+	rfid
+	b	.
 
 	.align	7
 _GLOBAL(do_stab_bolted_pSeries)
@@ -952,7 +987,8 @@ fast_exception_return:
 	REST_8GPRS(2, r1)
 
 	mfmsr	r10
-	clrrdi	r10,r10,2		/* clear RI (LE is 0 already) */
+	rldicl	r10,r10,48,1		/* clear EE */
+	rldicr	r10,r10,16,61		/* clear RI (LE is 0 already) */
 	mtmsrd	r10,1
 
 	mtspr	SPRN_SRR1,r12
@@ -1877,11 +1913,16 @@ _GLOBAL(__secondary_start)
 	/* enable MMU and jump to start_secondary */
 	LOAD_REG_ADDR(r3, .start_secondary_prolog)
 	LOAD_REG_IMMEDIATE(r4, MSR_KERNEL)
-#ifdef DO_SOFT_DISABLE
+#ifdef CONFIG_PPC_ISERIES
 BEGIN_FW_FTR_SECTION
 	ori	r4,r4,MSR_EE
 END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
 #endif
+BEGIN_FW_FTR_SECTION
+	stb	r7,PACASOFTIRQEN(r13)
+	stb	r7,PACAHARDIRQEN(r13)
+END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES)
+
 	mtspr	SPRN_SRR0,r3
 	mtspr	SPRN_SRR1,r4
 	rfid
@@ -2019,15 +2060,18 @@ _STATIC(start_here_common)
 
 	/* Load up the kernel context */
 5:
-#ifdef DO_SOFT_DISABLE
-BEGIN_FW_FTR_SECTION
 	li	r5,0
-	stb	r5,PACAPROCENABLED(r13)	/* Soft Disabled */
+	stb	r5,PACASOFTIRQEN(r13)	/* Soft Disabled */
+#ifdef CONFIG_PPC_ISERIES
+BEGIN_FW_FTR_SECTION
 	mfmsr	r5
 	ori	r5,r5,MSR_EE		/* Hard Enabled */
 	mtmsrd	r5
 END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
 #endif
+BEGIN_FW_FTR_SECTION
+	stb	r5,PACAHARDIRQEN(r13)
+END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES)
 
 	bl .start_kernel