x86/apic: Remove the (now) unused disable_IO_APIC() function

No one uses it anymore.
Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: douly.fnst@cn.fujitsu.com
Cc: joro@8bytes.org
Cc: prarit@redhat.com
Cc: uobergfe@redhat.com
Link: http://lkml.kernel.org/r/20180214054656.3780-5-bhe@redhat.com
[ Rewrote the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/io_apic.h

@@ -192,7 +192,6 @@ static inline unsigned int io_apic_read(unsigned int apic, unsigned int reg)
 
 extern void setup_IO_APIC(void);
 extern void enable_IO_APIC(void);
-extern void disable_IO_APIC(void);
 extern void clear_IO_APIC(void);
 extern void restore_boot_irq_mode(void);
 extern int IO_APIC_get_PCI_irq_vector(int bus, int devfn, int pin);

arch/x86/kernel/apic/io_apic.c

@@ -1438,19 +1438,6 @@ void native_disable_io_apic(void)
 		disconnect_bsp_APIC(ioapic_i8259.pin != -1);
 }
 
-/*
- * Not an __init, needed by the reboot code
- */
-void disable_IO_APIC(void)
-{
-	/*
-	 * Clear the IO-APIC before rebooting:
-	 */
-	clear_IO_APIC();
-
-	restore_boot_irq_mode();
-}
-
 void restore_boot_irq_mode(void)
 {
 	if (!nr_legacy_irqs())

arch/x86/kernel/machine_kexec_32.c

@@ -195,9 +195,8 @@ void machine_kexec(struct kimage *image)
 		/*
 		 * We need to put APICs in legacy mode so that we can
 		 * get timer interrupts in second kernel. kexec/kdump
-		 * paths already have calls to disable_IO_APIC() in
-		 * one form or other. kexec jump path also need
-		 * one.
+		 * paths already have calls to restore_boot_irq_mode()
+		 * in one form or other. kexec jump path also need one.
 		 */
 		clear_IO_APIC();
 		restore_boot_irq_mode();

arch/x86/kernel/machine_kexec_64.c

@@ -293,9 +293,8 @@ void machine_kexec(struct kimage *image)
 		/*
 		 * We need to put APICs in legacy mode so that we can
 		 * get timer interrupts in second kernel. kexec/kdump
-		 * paths already have calls to disable_IO_APIC() in
-		 * one form or other. kexec jump path also need
-		 * one.
+		 * paths already have calls to restore_boot_irq_mode()
+		 * in one form or other. kexec jump path also need one.
 		 */
 		clear_IO_APIC();
 		restore_boot_irq_mode();