From fb209bd891645bb87b9618b724f0b4928e0df3de Mon Sep 17 00:00:00 2001 From: Yinghai Lu Date: Wed, 21 Dec 2011 17:45:17 -0800 Subject: x86, x2apic: Fallback to xapic when BIOS doesn't setup interrupt-remapping On some of the recent Intel SNB platforms, by default bios is pre-enabling x2apic mode in the cpu with out setting up interrupt-remapping. This case was resulting in the kernel to panic as the cpu is already in x2apic mode but the OS was not able to enable interrupt-remapping (which is a pre-req for using x2apic capability). On these platforms all the apic-ids are < 255 and the kernel can fallback to xapic mode if the bios has not enabled interrupt-remapping (which is mostly the case if the bios has not exported interrupt-remapping tables to the OS). Reported-by: Berck E. Nash Signed-off-by: Yinghai Lu Link: http://lkml.kernel.org/r/20111222014632.600418637@sbsiddha-desk.sc.intel.com Signed-off-by: Suresh Siddha Signed-off-by: H. Peter Anvin --- arch/x86/kernel/apic/io_apic.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'arch/x86/kernel/apic/io_apic.c') diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index 6d939d7847e2..45b461fdb344 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -2948,6 +2948,10 @@ static inline void __init check_timer(void) } local_irq_disable(); apic_printk(APIC_QUIET, KERN_INFO "..... failed :(.\n"); + if (x2apic_preenabled) + apic_printk(APIC_QUIET, KERN_INFO + "Perhaps problem with the pre-enabled x2apic mode\n" + "Try booting with x2apic and interrupt-remapping disabled in the bios.\n"); panic("IO-APIC + timer doesn't work! Boot with apic=debug and send a " "report. Then try booting with the 'noapic' option.\n"); out: -- cgit v1.2.3