[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>

2 files changed, 2 insertions, 39 deletions

diff --git a/arch/powerpc/platforms/iseries/ksyms.c b/arch/powerpc/platforms/iseries/ksyms.c
index a2200842f4e..2430848b98e 100644
--- a/arch/powerpc/platforms/iseries/ksyms.c
+++ b/arch/powerpc/platforms/iseries/ksyms.c
@@ -19,9 +19,3 @@ EXPORT_SYMBOL(HvCall4);
 EXPORT_SYMBOL(HvCall5);
 EXPORT_SYMBOL(HvCall6);
 EXPORT_SYMBOL(HvCall7);
-
-#ifdef CONFIG_SMP
-EXPORT_SYMBOL(local_get_flags);
-EXPORT_SYMBOL(local_irq_disable);
-EXPORT_SYMBOL(local_irq_restore);
-#endif
diff --git a/arch/powerpc/platforms/iseries/misc.S b/arch/powerpc/platforms/iseries/misc.S
index 7641fc7e550..2c6ff0fdac9 100644
--- a/arch/powerpc/platforms/iseries/misc.S
+++ b/arch/powerpc/platforms/iseries/misc.S
@@ -19,39 +19,8 @@
 
 	.text
 
-/* unsigned long local_save_flags(void) */
-_GLOBAL(local_get_flags)
-	lbz	r3,PACAPROCENABLED(r13)
-	blr
-
-/* unsigned long local_irq_disable(void) */
-_GLOBAL(local_irq_disable)
-	lbz	r3,PACAPROCENABLED(r13)
-	li	r4,0
-	stb	r4,PACAPROCENABLED(r13)
-	blr			/* Done */
-
-/* void local_irq_restore(unsigned long flags) */
-_GLOBAL(local_irq_restore)
-	lbz	r5,PACAPROCENABLED(r13)
-	 /* Check if things are setup the way we want _already_. */
-	cmpw	0,r3,r5
-	beqlr
-	/* are we enabling interrupts? */
-	cmpdi	0,r3,0
-	stb	r3,PACAPROCENABLED(r13)
-	beqlr
-	/* Check pending interrupts */
-	/*   A decrementer, IPI or PMC interrupt may have occurred
-	 *   while we were in the hypervisor (which enables) */
-	ld	r4,PACALPPACAPTR(r13)
-	ld	r4,LPPACAANYINT(r4)
-	cmpdi	r4,0
-	beqlr
-
-	/*
-	 * Handle pending interrupts in interrupt context
-	 */
+/* Handle pending interrupts in interrupt context */
+_GLOBAL(iseries_handle_interrupts)
 	li	r0,0x5555
 	sc
 	blr