x86: Avoid building unused IRQ entry stubs

When X86_LOCAL_APIC (i.e. unconditionally on x86-64),
first_system_vector will never end up being higher than
LOCAL_TIMER_VECTOR (0xef), and hence building stubs for vectors
0xef...0xff is pointlessly reducing code density. Deal with this at
build time already.

Taking into consideration that X86_64 implies X86_LOCAL_APIC, also
simplify (and hence make easier to read and more consistent with the
change done here) some #if-s in arch/x86/kernel/irqinit.c.

While we could further improve the packing of the IRQ entry stubs (the
four ones now left in the last set could be fit into the four padding
bytes each of the final four sets have) this doesn't seem to provide
any real benefit: Both irq_entries_start and common_interrupt getting
cache line aligned, eliminating the 30th set would just produce 32
bytes of padding between the 29th and common_interrupt.

[ tglx: Folded lguest fix from Dan Carpenter ]

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: lguest@lists.ozlabs.org
Cc: Rusty Russell <rusty@rustcorp.com.au>
Link: http://lkml.kernel.org/r/54574D5F0200007800044389@mail.emea.novell.com
Link: http://lkml.kernel.org/r/20141115185718.GB6530@mwanda
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 9 insertions, 4 deletions

diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
index 4de73ee78361..fa893087fb51 100644
--- a/arch/x86/kernel/irqinit.c
+++ b/arch/x86/kernel/irqinit.c
@@ -124,7 +124,6 @@ void setup_vector_irq(int cpu)
 static void __init smp_intr_init(void)
 {
 #ifdef CONFIG_SMP
-#if defined(CONFIG_X86_64) || defined(CONFIG_X86_LOCAL_APIC)
         /*
          * The reschedule interrupt is a CPU-to-CPU reschedule-helper
          * IPI, driven by wakeup.
@@ -144,7 +143,6 @@ static void __init smp_intr_init(void)
 
         /* IPI used for rebooting/stopping */
         alloc_intr_gate(REBOOT_VECTOR, reboot_interrupt);
-#endif
 #endif /* CONFIG_SMP */
 }
 
@@ -159,7 +157,7 @@ static void __init apic_intr_init(void)
         alloc_intr_gate(THRESHOLD_APIC_VECTOR, threshold_interrupt);
 #endif
 
-#if defined(CONFIG_X86_64) || defined(CONFIG_X86_LOCAL_APIC)
+#ifdef CONFIG_X86_LOCAL_APIC
         /* self generated IPI for local APIC timer */
         alloc_intr_gate(LOCAL_TIMER_VECTOR, apic_timer_interrupt);
 
@@ -197,10 +195,17 @@ void __init native_init_IRQ(void)
          * 'special' SMP interrupts)
          */
         i = FIRST_EXTERNAL_VECTOR;
-        for_each_clear_bit_from(i, used_vectors, NR_VECTORS) {
+#ifndef CONFIG_X86_LOCAL_APIC
+#define first_system_vector NR_VECTORS
+#endif
+        for_each_clear_bit_from(i, used_vectors, first_system_vector) {
                 /* IA32_SYSCALL_VECTOR could be used in trap_init already. */
                 set_intr_gate(i, interrupt[i - FIRST_EXTERNAL_VECTOR]);
         }
+#ifdef CONFIG_X86_LOCAL_APIC
+        for_each_clear_bit_from(i, used_vectors, NR_VECTORS)
+                set_intr_gate(i, spurious_interrupt);
+#endif
 
         if (!acpi_ioapic && !of_ioapic && nr_legacy_irqs())
                 setup_irq(2, &irq2);