s390/irqflags: optimize irq restore

The ssm instruction takes longer that stnsm/stosm as it is often
used to modify DAT and PER. We know that irqsave/irqrestore only
deals with external and I/O interrupts and we know that irqrestore
can transition only from disabled->disabled or disabled->enabled,
so we can use the faster stosm.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/arch/s390/include/asm/irqflags.h b/arch/s390/include/asm/irqflags.h
index 16aa0c779e0762e210fe6652a0a5efda24771381..595a275c36f87d5ea4fa58d0a580eb36c601ef34 100644 (file)
--- a/arch/s390/include/asm/irqflags.h
+++ b/arch/s390/include/asm/irqflags.h
@@ -8,6 +8,8 @@
 
 #include <linux/types.h>
 
+#define ARCH_IRQ_ENABLED       (3UL << (BITS_PER_LONG - 8))
+
 /* store then OR system mask. */
 #define __arch_local_irq_stosm(__or)                                   \
 ({                                                                     \
@@ -54,14 +56,17 @@ static inline notrace void arch_local_irq_enable(void)
        __arch_local_irq_stosm(0x03);
 }
 
+/* This only restores external and I/O interrupt state */
 static inline notrace void arch_local_irq_restore(unsigned long flags)
 {
-       __arch_local_irq_ssm(flags);
+       /* only disabled->disabled and disabled->enabled is valid */
+       if (flags & ARCH_IRQ_ENABLED)
+               arch_local_irq_enable();
 }
 
 static inline notrace bool arch_irqs_disabled_flags(unsigned long flags)
 {
-       return !(flags & (3UL << (BITS_PER_LONG - 8)));
+       return !(flags & ARCH_IRQ_ENABLED);
 }
 
 static inline notrace bool arch_irqs_disabled(void)

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index c722400c769784d8df6f13507693e117ad942497..73e29033709285b44ceb5609919c07aff86e9de9 100644 (file)
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -98,7 +98,7 @@ void __init paging_init(void)
        __ctl_load(S390_lowcore.kernel_asce, 1, 1);
        __ctl_load(S390_lowcore.kernel_asce, 7, 7);
        __ctl_load(S390_lowcore.kernel_asce, 13, 13);
-       arch_local_irq_restore(4UL << (BITS_PER_LONG - 8));
+       __arch_local_irq_stosm(0x04);
 
        sparse_memory_present_with_active_regions(MAX_NUMNODES);
        sparse_init();