[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, 23 insertions, 11 deletions

diff --git a/include/asm-powerpc/hw_irq.h b/include/asm-powerpc/hw_irq.h
index d40359204aba..c4a1ab608f6f 100644
--- a/include/asm-powerpc/hw_irq.h
+++ b/include/asm-powerpc/hw_irq.h
@@ -7,16 +7,30 @@
 #ifdef __KERNEL__
 
 #include <linux/errno.h>
+#include <linux/compiler.h>
 #include <asm/ptrace.h>
 #include <asm/processor.h>
 
 extern void timer_interrupt(struct pt_regs *);
 
-#ifdef CONFIG_PPC_ISERIES
+#ifdef CONFIG_PPC64
+#include <asm/paca.h>
+
+static inline unsigned long local_get_flags(void)
+{
+        return get_paca()->soft_enabled;
+}
+
+static inline unsigned long local_irq_disable(void)
+{
+        unsigned long flag = get_paca()->soft_enabled;
+        get_paca()->soft_enabled = 0;
+        barrier();
+        return flag;
+}
 
-extern unsigned long local_get_flags(void);
-extern unsigned long local_irq_disable(void);
 extern void local_irq_restore(unsigned long);
+extern void iseries_handle_interrupts(void);
 
 #define local_irq_enable()      local_irq_restore(1)
 #define local_save_flags(flags) ((flags) = local_get_flags())
@@ -24,17 +38,14 @@ extern void local_irq_restore(unsigned long);
 
 #define irqs_disabled()         (local_get_flags() == 0)
 
+#define hard_irq_enable()       __mtmsrd(mfmsr() | MSR_EE, 1)
+#define hard_irq_disable()      __mtmsrd(mfmsr() & ~MSR_EE, 1)
+
 #else
 
 #if defined(CONFIG_BOOKE)
 #define SET_MSR_EE(x)   mtmsr(x)
 #define local_irq_restore(flags)        __asm__ __volatile__("wrtee %0" : : "r" (flags) : "memory")
-#elif defined(__powerpc64__)
-#define SET_MSR_EE(x)   __mtmsrd(x, 1)
-#define local_irq_restore(flags) do { \
-        __asm__ __volatile__("": : :"memory"); \
-        __mtmsrd((flags), 1); \
-} while(0)
 #else
 #define SET_MSR_EE(x)   mtmsr(x)
 #define local_irq_restore(flags)        mtmsr(flags)
@@ -81,7 +92,7 @@ static inline void local_irq_save_ptr(unsigned long *flags)
 #define local_irq_save(flags)   local_irq_save_ptr(&flags)
 #define irqs_disabled()         ((mfmsr() & MSR_EE) == 0)
 
-#endif /* CONFIG_PPC_ISERIES */
+#endif /* CONFIG_PPC64 */
 
 #define mask_irq(irq)                                           \
         ({                                                      \
diff --git a/include/asm-powerpc/paca.h b/include/asm-powerpc/paca.h
index 0a4e5c93e8e6..0d3adc09c847 100644
--- a/include/asm-powerpc/paca.h
+++ b/include/asm-powerpc/paca.h
@@ -93,7 +93,8 @@ struct paca_struct {
         u64 stab_rr;                    /* stab/slb round-robin counter */
         u64 saved_r1;                   /* r1 save for RTAS calls */
         u64 saved_msr;                  /* MSR saved here by enter_rtas */
-        u8 proc_enabled;                /* irq soft-enable flag */
+        u8 soft_enabled;                /* irq soft-enable flag */
+        u8 hard_enabled;                /* set if irqs are enabled in MSR */
         u8 io_sync;                     /* writel() needs spin_unlock sync */
 
         /* Stuff for accurate time accounting */