irq: initialize nr_irqs based on nr_cpu_ids

Impact: Reduce memory usage.

This is the second half of the changes to make the irq_desc_ptrs be
variable sized based on nr_cpu_ids.  This is done by adding a new
"max_nr_irqs" macro to irq_vectors.h (and a dummy in irqnr.h) to
return a max NR_IRQS value based on NR_CPUS or nr_cpu_ids.

This necessitated moving the define of MAX_IO_APICS to a separate
file (asm/apicnum.h) so it could be included without the baggage
of the other asm/apicdef.h declarations.

Signed-off-by: Mike Travis <travis@sgi.com>

5 files changed, 35 insertions, 11 deletions

diff --git a/arch/x86/include/asm/apicdef.h b/arch/x86/include/asm/apicdef.h
index 63134e31e8b9..1a6454ef7f6c 100644
--- a/arch/x86/include/asm/apicdef.h
+++ b/arch/x86/include/asm/apicdef.h
@@ -132,12 +132,8 @@
 #define APIC_BASE_MSR   0x800
 #define X2APIC_ENABLE   (1UL << 10)
 
-#ifdef CONFIG_X86_32
-# define MAX_IO_APICS 64
-#else
-# define MAX_IO_APICS 128
-# define MAX_LOCAL_APIC 32768
-#endif
+/* get MAX_IO_APICS */
+#include <asm/apicnum.h>
 
 /*
  * All x86-64 systems are xAPIC compatible.
diff --git a/arch/x86/include/asm/apicnum.h b/arch/x86/include/asm/apicnum.h
new file mode 100644
index 000000000000..82f613c607ce
--- /dev/null
+++ b/arch/x86/include/asm/apicnum.h
@@ -0,0 +1,12 @@
+#ifndef _ASM_X86_APICNUM_H
+#define _ASM_X86_APICNUM_H
+
+/* define MAX_IO_APICS */
+#ifdef CONFIG_X86_32
+# define MAX_IO_APICS 64
+#else
+# define MAX_IO_APICS 128
+# define MAX_LOCAL_APIC 32768
+#endif
+
+#endif /* _ASM_X86_APICNUM_H */
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index f7ff65032b9d..602361ad0e74 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -105,6 +105,8 @@
 
 #if defined(CONFIG_X86_IO_APIC) && !defined(CONFIG_X86_VOYAGER)
 
+#include <asm/apicnum.h>        /* need MAX_IO_APICS */
+
 #ifndef CONFIG_SPARSE_IRQ
 # if NR_CPUS < MAX_IO_APICS
 #  define NR_IRQS (NR_VECTORS + (32 * NR_CPUS))
@@ -112,11 +114,15 @@
 #  define NR_IRQS (NR_VECTORS + (32 * MAX_IO_APICS))
 # endif
 #else
-# if (8 * NR_CPUS) > (32 * MAX_IO_APICS)
-#  define NR_IRQS (NR_VECTORS + (8 * NR_CPUS))
-# else
-#  define NR_IRQS (NR_VECTORS + (32 * MAX_IO_APICS))
-# endif
+
+/* defined as a macro so nr_irqs = max_nr_irqs(nr_cpu_ids) can be used */
+# define max_nr_irqs(nr_cpus)                           \
+        ((8 * nr_cpus) > (32 * MAX_IO_APICS) ?          \
+                (NR_VECTORS + (8 * NR_CPUS)) :          \
+                (NR_VECTORS + (32 * MAX_IO_APICS)))     \
+
+# define NR_IRQS max_nr_irqs(NR_CPUS)
+
 #endif
 
 #elif defined(CONFIG_X86_VOYAGER)
diff --git a/include/linux/irqnr.h b/include/linux/irqnr.h
index 86af92e9e84c..de66e4e10406 100644
--- a/include/linux/irqnr.h
+++ b/include/linux/irqnr.h
@@ -20,11 +20,18 @@
 
 # define for_each_irq_desc_reverse(irq, desc)                          \
         for (irq = nr_irqs - 1; irq >= 0; irq--)
+
 #else /* CONFIG_GENERIC_HARDIRQS */
 
+#include <asm/irq_vectors.h>    /* need possible max_nr_irqs() */
+
 extern int nr_irqs;
 extern struct irq_desc *irq_to_desc(unsigned int irq);
 
+# ifndef max_nr_irqs
+#  define max_nr_irqs(nr_cpus)  NR_IRQS
+# endif
+
 # define for_each_irq_desc(irq, desc)                                   \
         for (irq = 0, desc = irq_to_desc(irq); irq < nr_irqs;           \
              irq++, desc = irq_to_desc(irq))                            \
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index d0b8f7e72790..ebba7a116f14 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -133,6 +133,9 @@ int __init early_irq_init(void)
         int legacy_count;
         int i;
 
+        /* initialize nr_irqs based on nr_cpu_ids */
+        nr_irqs = max_nr_irqs(nr_cpu_ids);
+
         printk(KERN_INFO "NR_IRQS:%d nr_irqs:%d\n", NR_IRQS, nr_irqs);
 
         desc = irq_desc_legacy;