linux-kernel - Re: [RFC PATCH 1/1] PCI: skip release and reallocation of io port resources

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Message-Id: <201007090950.47269.bjorn.helgaas@hp.com>
Date:	Fri, 9 Jul 2010 09:50:45 -0600
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Ram Pai <linuxram@...ibm.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, clemens@...isch.de
Subject: Re: [RFC PATCH 1/1] PCI: skip release and reallocation of io port resources

On Tuesday, July 06, 2010 06:49:32 pm Yinghai Lu wrote:
> On 07/06/2010 04:58 PM, Linus Torvalds wrote:
> > On Tue, Jul 6, 2010 at 4:13 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> >>
> >> So you want to use pci=override_bios to reallocate all bios assigned resource include
> >> peer root buses resources and pci bridge resource and pci devices BAR?
> > 
> > In a perfect world, we'd never need this at all, but sicne that's not
> > an option, the second-best alternative might be something like the
> > following:
> > 
> >   pci=override=off # default
> >   pci=override=conflict # override only on conflicts
> >   pci=override=<device> # clear BIOS allocations for <device> (and any
> > children, if it's a bus)
> 
> current:
> if there is conflict, like pci bridge resources or pci devices resources is not in the scope of peer root bus resource range.
> or pci devices is not in pci bridge resources range.
> kernel would reject the resource and try to get new range in parent resource for the children.
> 
> so current default is overriding the conflicts already.

One conflict we don't handle correctly is when we find a device that
doesn't fit inside the root bus resources.  We currently disable the
device, but Windows just leaves it where BIOS put it.

This causes this bug: https://bugzilla.kernel.org/show_bug.cgi?id=16263
It should be fairly simple to make Linux handle this conflict the same
way, without requiring any special kernel arguments.

Bjorn
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