linux-kernel - Re: [Patch 1/1] x86 pci: Add option to not assign BAR's if not already assigned

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Date:	Fri, 14 May 2010 15:47:06 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Mike Travis <travis@....com>
Cc:	Bjorn Helgaas <bjorn.helgaas@...com>, Mike Habeck <habeck@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Jacob Pan <jacob.jun.pan@...el.com>, Tejun Heo <tj@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Yinghai <yinghai.lu@...cle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Myron Stowe <myron.stowe@...com>
Subject: Re: [Patch 1/1] x86 pci: Add option to not assign BAR's if not
 already assigned

On Fri, 14 May 2010 15:34:01 -0700
Mike Travis <travis@....com> wrote:

> 
> 
> Jesse Barnes wrote:
> > On Thu, 13 May 2010 14:02:30 -0600
> > Bjorn Helgaas <bjorn.helgaas@...com> wrote:
> >>>> This issue is not specific to x86, so I don't really like having
> >>>> the implementation be x86-specific.
> >>> I agree this isn't a x86 specific issue but given the 'norom'
> >>> cmdline option is basically doing the same thing (but for pci
> >>> Expansion ROM BARs) this code was modeled after it.
> 
> >> IMHO, we should fix both.
> > 
> > Yeah, that would be good.  Mike, have you looked at this at all?
> > 
> > Also, to clarify, this isn't affecting users today, right?  Or do you
> > need all this I/O space for multiple IOHs and the drivers that bind to
> > them in current UV systems?
> 
> We have customers that want to install more than 16 PCI-e cards right
> now.  Our window of opportunity closes very soon (days), so either this
> patch makes it in as is (or something close), or we wait for another
> release cycle.  UV shipments start this month.
> 
> [I wouldn't mind working on an improvement for later.]

Wow and they're using cards that want to use I/O space?  Funky.  It's
too late to get this into 2.6.34, but that can't be what you were
expecting... I don't see a problem with getting something like this in
for 2.6.35.

> > Fundamentally, until we have real dynamic PCI resource management (i.e.
> > driver hooks for handling relocation, lazy allocation of resources at
> > driver bind time, etc.) we're going to continue to need hacks like
> > this.  However, we could make them slightly more automated by making
> > "nobar" and "norom" the default on systems that typically need them,
> > maybe with a DMI table.
> 
> It seems that BIOS changes are much more difficult.  The real solution
> to this problem is for Card Vendors to not request I/O Bars if they
> won't be using them.  But that's the hardest option of all to accomplish.

Right.

-- 
Jesse Barnes, Intel Open Source Technology Center
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