Re: [GIT PULL] x86/uapi for 3.8

[Matt Fleming]

On Sat, 2012-12-15 at 17:35 +0100, Markus Trippelsdorf wrote:
> On 2012.12.15 at 17:33 +0100, Markus Trippelsdorf wrote:
> > On 2012.12.14 at 17:47 -0800, Linus Torvalds wrote:
> > > On Fri, Dec 14, 2012 at 5:41 PM, Linus Torvalds
> > > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> > > > I was wrong. It's not the x86 UAPI split, it's the DT pull. More people added.
> > > 
> > > Looking at the merge (just in case it could have done something odd),
> > > I'm starting to worry that this is some nasty heisenbug, and my
> > > bisection is not trustworthy at all. Because the DT pull sure as heck
> > > doesn't look like a likely candidate for anything either.
> > > 
> > > Ho humm. Anybody else see anything strange?
> > 
> > Yes. I'm seeing a BUG early during boot on my machine (RIP=NULL):
> >  
> >  BUG: unable to handle kernel NULL pointer dereference at           (null)
> > 
> > This is caused by:
> > 
> > commit 53b87cf088e2ea68d7c59619d0214cc15bb76133
> > Author: Matt Fleming <matt.fleming@xxxxxxxxx>
> > Date:   Fri Sep 7 18:23:51 2012 +0100
> > 
> >     x86, mm: Include the entire kernel memory map in trampoline_pgd
> >     
> >     There are various pieces of code in arch/x86 that require a page table
> >     with an identity mapping. Make trampoline_pgd a proper kernel page
> >     table, it currently only includes the kernel text and module space
> >     mapping.
> >     
> >     One new feature of trampoline_pgd is that it now has mappings for the
> >     physical I/O device addresses, which are inserted at ioremap()
> >     time. Some broken implementations of EFI firmware require these
> >     mappings to always be around.
> >     
> >     Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
> >     Signed-off-by: Matt Fleming <matt.fleming@xxxxxxxxx>
> > 
> 
> Adding Matt to CC.

Markus, could you please send me your full dmesg, or if possible the
dmesgs from both a working and non-working kernel.

After looking at your memory map layout, nothing immediately jumps out.

Could you try this revised patch and see if things work better? It's the
only thing I noticed that looked wrong with the original patch (apart
from the >512G ram bug that Yinghai pointed out).

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