Hi Ingo,

On Thu, 24 Mar 2011, Ingo Molnar wrote:
> * Pekka Enberg <penberg@kernel.org> wrote:
>
>> On Thu, Mar 24, 2011 at 4:41 PM, Christoph Lameter <cl@linux.com> wrote:
>>> On Thu, 24 Mar 2011, Ingo Molnar wrote:
>>>
>>>> FYI, some sort of boot crash has snuck upstream in the last 24 hours:
>>>>
>>>>  BUG: unable to handle kernel paging request at ffff87ffc147e020
>>>>  IP: [<ffffffff811aa762>] this_cpu_cmpxchg16b_emu+0x2/0x1c
>>>
>>> Hmmm.. This is the fallback code for the case that the processor does not
>>> support cmpxchg16b.
>>
>> How does alternative_io() work? Does it require
>> alternative_instructions() to be executed. If so, the fallback code
>> won't be active when we enter kmem_cache_init(). Is there any reason
>> check_bugs() is called so late during boot? Can we do something like
>> the totally untested attached patch?
>
> Does the config i sent you boot on your box? I think the bug is pretty generic
> and should trigger on any box.

Here's a patch that reorganizes the alternatives fixup to happen earlier 
so that the fallback should work. It boots on my machine so please give it 
a spin if possible.

I'll try out your .config next.

 			Pekka