Re: WARNING: at arch/x86/kernel/apic/apic.c:249 native_apic_write_dummy

[Cyrill Gorcunov <gorcunov@gmail.com>]

[Vegard Nossum - Wed, Jun 17, 2009 at 05:46:18PM +0200]
| 2009/6/17 Cyrill Gorcunov <gorcunov@gmail.com>:
| > [Vegard Nossum - Wed, Jun 17, 2009 at 05:11:20PM +0200]
| > | Hi,
| > |
| > | I just saw this warning on latest mainline when shutting down a box:
| [...]
| 
| > Thanks Vegard, will take a look.
| 
| I've attached full boot log (it's a different boot though).
| 
| 
| Vegard
...

Vegard, could you test the patch?

	-- Cyrill
---

If we have apic disabled we don't even switch to APIC mode and do not
calling for connect_bsp_APIC. Though on SMP compiled kernel the
native_machine_shutdown does try to write the apic register anyway.
Fix it with explicit check if we really should touch apic registers.

Reported-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---
 arch/x86/kernel/apic/io_apic.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Index: linux-2.6.git/arch/x86/kernel/apic/io_apic.c
=====================================================================
--- linux-2.6.git.orig/arch/x86/kernel/apic/io_apic.c
+++ linux-2.6.git/arch/x86/kernel/apic/io_apic.c
@@ -2003,7 +2003,9 @@ void disable_IO_APIC(void)
 	/*
 	 * Use virtual wire A mode when interrupt remapping is enabled.
 	 */
-	disconnect_bsp_APIC(!intr_remapping_enabled && ioapic_i8259.pin != -1);
+	if (cpu_has_apic)
+		disconnect_bsp_APIC(!intr_remapping_enabled &&
+				ioapic_i8259.pin != -1);
 }
 
 #ifdef CONFIG_X86_32