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Date: Mon, 10 Mar 2008 18:24:17 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       "Rafael J. Wysocki" <rjw@sisk.pl>, Len Brown <lenb@kernel.org>
Subject: Re: [patch] fix ACPI boot regression (was: Re: Linux 2.6.25-rc5)
Message-ID: <20080310172417.GA25898@elte.hu>
References: <alpine.LFD.1.00.0803092231580.5896@woody.linux-foundation.org> <20080310170434.GA22430@elte.hu> <alpine.LFD.1.00.0803101011580.5896@woody.linux-foundation.org>
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Mon, 10 Mar 2008, Ingo Molnar wrote:
> >
> > so zero-extending the result in the PCI-BIOS read routine fixes the 
> > regression on my laptop. ( It might fix some other long-standing 
> > issues we had with PCI-BIOS during the past decade ... ) Both 8-bit 
> > and 16-bit accesses were buggy.
> 
> Oh, wow. That must have been there forever, but very few people 
> probably ever cared.
> 
> And why is your laptop using the BIOS routines anyway? Or was that 
> just a result of your randconfig having turned off the sane config 
> access routines?

yeah, randconfig generated this:

  CONFIG_PCI=y
  CONFIG_PCI_GOBIOS=y
  # CONFIG_PCI_GOMMCONFIG is not set
  # CONFIG_PCI_GODIRECT is not set
  # CONFIG_PCI_GOANY is not set
  CONFIG_PCI_BIOS=y

which forced the PCI code into the BIOS access method on this otherwise 
modern system. I disable some of the really-known-to-be-broken .config 
options in randconfig - but i still bravely keept CONFIG_GO_PCIBIOS in 
the randomized space, which triggered this.

On another box, which has a different BIOS, this bug never happened, in 
tens of thousands of bootup tests.

	Ingo