linux-kernel - Re: [GIT PULL] x86/uapi for 3.8

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Date:	Sun, 16 Dec 2012 14:25:21 +0100
From:	Markus Trippelsdorf <markus@...ppelsdorf.de>
To:	Matt Fleming <matt.fleming@...el.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Guennadi Liakhovetski <g.liakhovetski@....de>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>, Dave Jones <davej@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [GIT PULL] x86/uapi for 3.8

On 2012.12.16 at 12:43 +0000, Matt Fleming wrote:
> 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@...ux-foundation.org> 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@...el.com>
> > > 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@...e.com>
> > >     Signed-off-by: Matt Fleming <matt.fleming@...el.com>
> > > 
> > 
> > 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).

Matt, your patch fixes the problem for me. Thanks.

-- 
Markus

View attachment "dmesg" of type "text/plain" (31902 bytes)