[PATCH] x86/idt: Simplify the idt_setup_apic_and_irq_gates()

[Dou Liyang]

The vectors between FIRST_SYSTEM_VECTOR and NR_VECTORS are special IRQ
vectors used by the SMP architecture. But, if X86_LOCAL_APIC=n, it will
not be used, and the FIRST_SYSTEM_VECTOR is equal to NR_VECTORS.

idt_setup_apic_and_irq_gates() didn't notice that, which make the code
a little complex.

Remove the code of the X86_LOCAL_APIC=n case to simplify it.

Signed-off-by: Dou Liyang <douly.fnst@xxxxxxxxxxxxxx>
---
 arch/x86/kernel/idt.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index 2c3a1b4294eb..8b4174890706 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -317,15 +317,16 @@ void __init idt_setup_apic_and_irq_gates(void)
 		set_intr_gate(i, entry);
 	}
 
-	for_each_clear_bit_from(i, system_vectors, NR_VECTORS) {
+	/*
+	 * If X86_LOCAL_APIC=n, the FIRST_SYSTEM_VECTOR is equal to NR_VECTORS
+	 * Just consider the X86_LOCAL_APIC=y case
+	 */
 #ifdef CONFIG_X86_LOCAL_APIC
+	for_each_clear_bit_from(i, system_vectors, NR_VECTORS) {
 		set_bit(i, system_vectors);
 		set_intr_gate(i, spurious_interrupt);
-#else
-		entry = irq_entries_start + 8 * (i - FIRST_EXTERNAL_VECTOR);
-		set_intr_gate(i, entry);
-#endif
 	}
+#endif
 }
 
 /**
-- 
2.14.3