From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Wright <chrisw@sous-sol.org>
Subject: Re: Query on IOMMU
Date: Wed, 22 Dec 2010 06:56:46 -0800
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Cc: Chris Wright <chrisw@sous-sol.org>,
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To: Prasad Joshi <P.G.Joshi@student.reading.ac.uk>
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* Prasad Joshi (P.G.Joshi@student.reading.ac.uk) wrote:
> Is the answer 
> 
> "All PCI buses located behind a PCI-PCI bridge must reside between the seondary bus number and the subordinate bus number (inclusive)."
> 
> 00:14.4 PCI bridge: ATI Technologies Inc SBx00 PCI to PCI Bridge
>                       Bus: primary=00, secondary=01, subordinate=01, sec-latency=64
> 
> So all the PCI devices between secondary (01) and subordinate (01) (in this case same) are behind the PCI Bridge. Correct me if I am wrong.

That's correct.  You'll find secondary < subordinate when there's
another bridge downstream.

> 01:05.0 Ethernet controller: Intel Corporation 82557/8/9/0/1 Ethernet Pro 100 (rev 0c)
> As Bus ID is 01 this ethernet controller is behind the PCI Bridge

Yup.

> 03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 06)
> As Bus: 03, I can assume this is not behind the PCI Bridge
> 
> But if subordinate would have been, say 03 or 04, then even this ethernet card (03:00:0) would be behind the PCI Bridge.
> 
> Am I correct?

That's right.

thanks,
-chris