netdev - Re: [PATCH] pciaer: report config read/write errors

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Date:	Tue, 02 Dec 2008 15:14:35 -0500
From:	Loic Prylli <loic@...i.com>
To:	Stephen Hemminger <shemminger@...tta.com>
CC:	David Miller <davem@...emloft.net>, jeffrey.t.kirsher@...el.com,
	netdev@...r.kernel.org, jeff@...zik.org,
	peter.p.waskiewicz.jr@...el.com, linux-pci@...r.kernel.org
Subject: Re: [PATCH] pciaer: report config read/write errors

On 12/02/2008 02:44 PM, Stephen Hemminger wrote:
> pci_find_ext_capability would succeed but all access to registers >= 256
> would fail if MMCONFIG failed. 

Your sentence seems self-contradicting to me. pci_find_ext_capability() 
(!=  pci_find_capability()) only tries to access registers >= 256, so I 
don't see how it would succeed if *all* those accesses are failing.

> P.s: you can look back into LKML for Linus discussion about why MMCONFIG
> is broken anyway.
>   

I was an active participant in one of those discussions (although it is 
possible I missed a later one), so I am quite aware about the 
limitations of MMCONFIG. But pci_find_ext_capability() looked to me a 
good filter to check about those limitations().

This is not just about pciaer, for instance, it might be that a lot of 
the SR-IOV code submitted recently assumes that if the corresponding 
extended-capability can be detected, little checking needs to be done 
afterwards.

Loic

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