[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, 18 insertions, 21 deletions

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 748e74fcf54..efda48741b2 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -87,6 +87,10 @@ system_call_common:
 	addi	r9,r1,STACK_FRAME_OVERHEAD
 	ld	r11,exception_marker@toc(r2)
 	std	r11,-16(r9)		/* "regshere" marker */
+	li	r10,1
+	stb	r10,PACASOFTIRQEN(r13)
+	stb	r10,PACAHARDIRQEN(r13)
+	std	r10,SOFTE(r1)
 #ifdef CONFIG_PPC_ISERIES
 BEGIN_FW_FTR_SECTION
 	/* Hack for handling interrupts when soft-enabling on iSeries */
@@ -94,8 +98,6 @@ BEGIN_FW_FTR_SECTION
 	andi.	r10,r12,MSR_PR		/* from kernel */
 	crand	4*cr0+eq,4*cr1+eq,4*cr0+eq
 	beq	hardware_interrupt_entry
-	lbz	r10,PACAPROCENABLED(r13)
-	std	r10,SOFTE(r1)
 END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
 #endif
 	mfmsr	r11
@@ -460,9 +462,9 @@ _GLOBAL(ret_from_except_lite)
 #endif
 
 restore:
+	ld	r5,SOFTE(r1)
 #ifdef CONFIG_PPC_ISERIES
 BEGIN_FW_FTR_SECTION
-	ld	r5,SOFTE(r1)
 	cmpdi	0,r5,0
 	beq	4f
 	/* Check for pending interrupts (iSeries) */
@@ -472,16 +474,16 @@ BEGIN_FW_FTR_SECTION
 	beq+	4f			/* skip do_IRQ if no interrupts */
 
 	li	r3,0
-	stb	r3,PACAPROCENABLED(r13)	/* ensure we are soft-disabled */
+	stb	r3,PACASOFTIRQEN(r13)	/* ensure we are soft-disabled */
 	ori	r10,r10,MSR_EE
 	mtmsrd	r10			/* hard-enable again */
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	.do_IRQ
 	b	.ret_from_except_lite		/* loop back and handle more */
-
-4:	stb	r5,PACAPROCENABLED(r13)
+4:
 END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
 #endif
+	stb	r5,PACASOFTIRQEN(r13)
 
 	ld	r3,_MSR(r1)
 	andi.	r0,r3,MSR_RI
@@ -538,25 +540,15 @@ do_work:
 	/* Check that preempt_count() == 0 and interrupts are enabled */
 	lwz	r8,TI_PREEMPT(r9)
 	cmpwi	cr1,r8,0
-#ifdef CONFIG_PPC_ISERIES
-BEGIN_FW_FTR_SECTION
 	ld	r0,SOFTE(r1)
 	cmpdi	r0,0
-END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
-#endif
-BEGIN_FW_FTR_SECTION
-	andi.	r0,r3,MSR_EE
-END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES)
 	crandc	eq,cr1*4+eq,eq
 	bne	restore
 	/* here we are preempting the current task */
 1:
-#ifdef CONFIG_PPC_ISERIES
-BEGIN_FW_FTR_SECTION
 	li	r0,1
-	stb	r0,PACAPROCENABLED(r13)
-END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
-#endif
+	stb	r0,PACASOFTIRQEN(r13)
+	stb	r0,PACAHARDIRQEN(r13)
 	ori	r10,r10,MSR_EE
 	mtmsrd	r10,1		/* reenable interrupts */
 	bl	.preempt_schedule
@@ -639,8 +631,7 @@ _GLOBAL(enter_rtas)
 	/* There is no way it is acceptable to get here with interrupts enabled,
 	 * check it with the asm equivalent of WARN_ON
 	 */
-	mfmsr	r6
-	andi.	r0,r6,MSR_EE
+	lbz	r0,PACASOFTIRQEN(r13)
 1:	tdnei	r0,0
 .section __bug_table,"a"
 	.llong	1b,__LINE__ + 0x1000000, 1f, 2f
@@ -649,7 +640,13 @@ _GLOBAL(enter_rtas)
 1:	.asciz	__FILE__
 2:	.asciz "enter_rtas"
 .previous
-	
+
+	/* Hard-disable interrupts */
+	mfmsr	r6
+	rldicl	r7,r6,48,1
+	rotldi	r7,r7,16
+	mtmsrd	r7,1
+
 	/* Unfortunately, the stack pointer and the MSR are also clobbered,
 	 * so they are saved in the PACA which allows us to restore
 	 * our original state after RTAS returns.