Re: [GIT PULL] x86/uapi for 3.8

From: Markus Trippelsdorf
Date: Sat Dec 15 2012 - 11:35:27 EST


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
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