linux-kernel - Re: [PATCH v2] PCI: Always set prefetchable base/limit upper32 registers

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Date:	Mon, 30 Nov 2009 17:23:02 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Grant Grundler <grundler@...isc-linux.org>
CC:	Alex Williamson <alex.williamson@...com>, jbarnes@...tuousgeek.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI: Always set prefetchable base/limit upper32	registers

Grant Grundler wrote:
> On Mon, Nov 30, 2009 at 05:03:32PM -0700, Grant Grundler wrote:
>> On Mon, Nov 30, 2009 at 02:51:44PM -0700, Alex Williamson wrote:
>>> Prior to 1f82de10 we always initialized the upper 32bits of the
>>> prefetchable memory window, regardless of the address range used.
>>> Now we only touch it for a >32bit address, which means the upper32
>>> registers remain whatever the BIOS initialized them too.
>>>
>>> It's valid for the BIOS to set the upper32 base/limit to
>>> 0xffffffff/0x00000000, which makes us program prefetchable ranges
>>> like 0xffffffffabc00000 - 0x00000000abc00000
>>>
>>> Revert the chunk of 1f82de10 that made this conditional so we always
>>> write the upper32 registers and remove now unused pref_mem64 variable.
>>>
>>> Signed-off-by: Alex Williamson <alex.williamson@...com>
>> Reviewed-by: Grant Grundler <grundler@...isc-linux.org>
> 
> NAK this - I messed up. Yinghai is correct. Something else is going on.
> 
> It might be perfectly OK to read 0xffffffffabc00000 if the bridge
> isn't using the upper32 Prefetchable register. Maybe the problem is
> some code is reading the upper32 value without checking that it's valid?

maybe Alex is using old lspci?

YH
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