linux-kernel - Re: [Fwd: Re: [PATCH 0/5]PCI: x86 MMCONFIG]

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Date:	Thu, 20 Dec 2007 13:30:16 -0500
From:	Tony Camuso <tcamuso@...hat.com>
To:	Matthew Wilcox <matthew@....cx>
CC:	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	linux-pci@...ey.karlin.mff.cuni.cz
Subject: Re: [Fwd: Re: [PATCH 0/5]PCI: x86 MMCONFIG]

Matthew Wilcox wrote:

> Bad deduction.  What's happening is that the write to the BAR is causing
> it to overlap the decode for mmconfig space.  So the mmconfig write to
> set the BAR back never gets through.
> 
> I have a different idea to fix this problem.  Instead of writing
> 0xffffffff, we could look for an unused bit of space in the E820 map and
> write, say, 0xdfffffff to the low 32-bits of a BAR.  Then it wouldn't
> overlap, and we could find its size using MMCONFIG.
> 
The BAR claims to be a 64-bit BAR.

> Does anyone know how Windows handles these machines?  Obviously, if it's
> using MMCONFIG, it'd have the same problems.  Does it just use type 1
> for initial sizing?  Or does it use type 1 for all accesses below 256
> bytes?
> 
As far as I know, Windows has a blacklist that limits systems with these
devices to legacy PCI config access.

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