Commit 60d79fd9 authored Dec 07, 2010 by Yinghai Lu Committed by Thomas Gleixner Dec 09, 2010

x86, ioapic: Avoid writing io_apic id if already correct



For 32bit mptable path, setup_ids_from_mpc() always writes the io_apic
id register, even there is no change needed.

Skip the write, when readout and mptable match.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
LKML-Reference: <4CFDF785.7010401@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent 0450193b

arch/x86/kernel/apic/io_apic.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -2007,9 +2007,12 @@ void __init setup_ioapic_ids_from_mpc_nocheck(void)
		= mp_ioapics[apic_id].apicid;

		/*
		* Read the right value from the MPC table and
		* write it into the ID register.
		* Update the ID register according to the right value
		* from the MPC table if they are different.
		*/
		if (mp_ioapics[apic_id].apicid == reg_00.bits.ID)
		continue;

		apic_printk(APIC_VERBOSE, KERN_INFO
		"...changing IO-APIC physical APIC ID to %d ...",
		mp_ioapics[apic_id].apicid);