Re: 2.6.28-rc6: early panic with boot option "nosmp"

[Wu Fengguang <fengguang.wu@intel.com>]

On Thu, Dec 04, 2008 at 12:13:43PM +0200, Andi Kleen wrote:
> On Thu, Dec 04, 2008 at 10:28:06AM +0800, Wu Fengguang wrote:
> > Hi,
> > 
> > The boot option "maxcpus=0" or "nosmp" makes kernel 2.6.28-rc6 panic
> > immediately after booting:
> > 
> > PANIC: early exception 0e rip 10:ffffffff8176d6ff error 0 cr2 9
> 
> It would be useful if you could look the ffffffff8176d6ff 
> address up in your System.map or using gdb.

addr2line -e vmlinux -f 0xffffffff8176d6ff  
__get_smp_config
/cc/linux-2.6/arch/x86/kernel/mpparse.c:607


 582 /*
 583  * Scan the memory blocks for an SMP configuration block.
 584  */
 585 static void __init __get_smp_config(unsigned int early)
 586 {  
 587         struct intel_mp_floating *mpf = mpf_found;
 588 
 589         if (x86_quirks->mach_get_smp_config) {
 590                 if (x86_quirks->mach_get_smp_config(early))
 591                         return;
 592         }
 593         if (acpi_lapic && early)
 594                 return;
 595         /*
 596          * ACPI supports both logical (e.g. Hyper-Threading) and physical
 597          * processors, where MPS only supports physical.
 598          */
 599         if (acpi_lapic && acpi_ioapic) {
 600                 printk(KERN_INFO "Using ACPI (MADT) for SMP configuration "
 601                        "information\n");
 602                 return;
 603         } else if (acpi_lapic)
 604                 printk(KERN_INFO "Using ACPI for processor (LAPIC) "
 605                        "configuration information\n");
 606 
 607         printk(KERN_INFO "Intel MultiProcessor Specification v1.%d\n",
 608                mpf->mpf_specification);

The exception raised on dereferencing mpf or mpf_found.

Thanks,
Fengguang