[kdb] KDB makes Nehalem hang at early boot until key press

[Martin Hicks]

On Fri, Oct 30, 2009 at 12:02:57PM +0200, Thomas Renninger wrote:
> 
> we currently have a problem with latest Intel CPUs/BIOSes:
> If the machine gets booted it hangs in:
> init/main.c:
> kdb_init();

Is this problem only on the latest Nehalem CPUs/BIOSes?  Can we have
more information about the machine?

We're using KDB on many released and pre-release Nehalem machines with
no problems.

> As soon as an irq via keyboard is triggered, the machine continues 
> booting and everything is fine.
> 
> Is this known already? Can someone point me to a patch?
> 
> If not, is there a repo having the latest code, I could try
> out whether the latest version works.

The latest code, against 2.6.31, is

git://oss.sgi.com/kdb/kdb.git

> 
> IMO something like the attached patch makes sense?
> This fixes the problem with kdb=off (our default).
> But I am anxious that kdb code could still get activitated somehow
> and the machine might oops when trying to access not initialized
> kdb structures? Could someone give an estimation how risky that
> patch really is?

I'd really rather fix the underlying problem.  I have no idea what that
might be though...

mh