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

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Message-ID: <4C039980.3020608@sgi.com>
Date:	Mon, 31 May 2010 04:12:00 -0700
From:	Mike Travis <travis@....com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	Jacob Pan <jacob.jun.pan@...el.com>, Tejun Heo <tj@...nel.org>,
	Mike Habeck <habeck@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Patch 1/1] x86 pci: Add option to not assign BAR's if not already
 assigned



H. Peter Anvin wrote:
> On 05/28/2010 10:10 AM, Mike Travis wrote:
>>
>> H. Peter Anvin wrote:
>>> On 05/28/2010 09:53 AM, Mike Travis wrote:
>>>> Any further consideration for this patch, or has it been rejected?
>>> Well, it's really up to Jesse, but as far as I can see, this patch is a
>>> net loss of functionality and doesn't actually add anything.  Without
>>> this patch, some resources that were not assigned by BIOS will be
>>> unreachable.  With this patch, *all* resources that were not assigned by
>>> BIOS will be unreachable...
>>>
>>> 	-hpa
>>>
>> Apparently you're missing the point of the patch?  The patch is needed
>> because BIOS is purposely not assigning I/O BAR's to devices that won't
>> use them, freeing up the resource for devices that do need them.  Where
>> is the "all" resources that are not reachable?
>>
> 
> No, the patch isn't needed for those.
> 
> Without your patch:
> 
> - Devices assigned by BIOS remain assigned;
> - Devices not assigned by BIOS get assigned until address space
>   exhausted.
> 
> With your patch:
> 
> - Devices assigned by BIOS remain assigned;
> - Devices not assigned by BIOS never get assigned at all.
> 
> What am I missing here?
> 
> 	-hpa
> 

BIOS still assigns the MMIO BAR's so the devices are alive.
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