linux-kernel - Re: [PATCH] x86/PCI: never allocate PCI MMIO resources below BIOS

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Message-Id: <201004261427.57229.bjorn.helgaas@hp.com>
Date:	Mon, 26 Apr 2010 14:27:56 -0600
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	Andy Isaacson <adi@...apodia.org>,
	"R. Andrew Bailey" <bailey@...mai.com>,
	Yinghai <yinghai.lu@...cle.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, guenter.roeck@...csson.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Renninger <trenn@...e.de>, yaneti@...lera.com
Subject: Re: [PATCH] x86/PCI: never allocate PCI MMIO resources below BIOS_END

On Monday 26 April 2010 01:31:35 pm Jesse Barnes wrote:
> On Mon, 26 Apr 2010 11:34:36 -0700
> Andy Isaacson <adi@...apodia.org> wrote:
> > On Fri, Apr 23, 2010 at 05:05:24PM -0600, Bjorn Helgaas wrote:

> > > commit 7fb707eb97fdf6dc4fa4b127f127f8d00223afc7
> > > Author: Bjorn Helgaas <bjorn.helgaas@...com>
> > > Date:   Fri Apr 23 15:22:10 2010 -0600
> > > 
> > > x86/PCI: never allocate PCI MMIO resources below BIOS_END
> > >     
> > > When we move a PCI device or assign resources to a device not configured
> > > by the BIOS, we want to avoid the BIOS region below 1MB.  Note that if the
> > > BIOS places devices below 1MB, we leave them there.
> > 
> > Works for me.  dmesg at
> > https://bugzilla.kernel.org/attachment.cgi?id=26150
> 
> Great, thanks for testing.  Applied this one to my for-linus tree.  

Thanks!

> I still think Yinghai's patches should go in as well (marking regions as
> busy seems like good housekeeping), but with this fixed they're a better
> fit for -next.

I'm a little concerned that those patches are a sledgehammer approach.
Previously, IORESOURCE_BUSY has basically been used for mutual exclusion
between drivers that would otherwise claim the same resource.  It hasn't
been used to guide resource assignment in the PCI/PNP/etc core.  Maybe
it's a good idea to also use IORESOURCE_BUSY there, but I'm not sure.
Right now it feels like undesirable overloading to me.

I think it also leads to at least one problem: Guenter's machine has no
VGA but has a PCI device that lives at 0xa0000.  The driver for that
device won't be able to request that region if the arch code has marked
it busy.

Bjorn
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