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Re: [Qemu-devel] [PATCH] pci: fix requester id to be the one on root bus

From: Peter Xu
Subject: Re: [Qemu-devel] [PATCH] pci: fix requester id to be the one on root bus
Date: Thu, 12 May 2016 12:43:06 +0800
User-agent: Mutt/1.5.24 (2015-08-30)

On Wed, May 11, 2016 at 09:22:03PM -0600, Alex Williamson wrote:
> PCI Express to PCI/PCI-X Bridge Specification rev 1.0
> 2.3 Assignment of Requester ID and Tag by the Bridge
> PCIe-to-PCI bridges assign a requester ID composed of the secondary bus
> number with devfn = 0.  Although often on real hardware, the root
> complex PCI bridge uses the actual bridge requester ID even though
> it's actually a PCIe bridge.  Linux assume that if a bridge has a PCIe
> capability with type PCIe-to-PCI/X bridge we use the secondary bus
> requester ID, if it has a PCIe capability with type PCI/X-to-PCIe, we
> use the bridge requester ID.  If it does not have a PCIe capability we
> use the bridge ID except for a few quirked devices known to use the
> secondary bus ID.  Yay standards!  Thanks,

Thanks Alex!

I have found pci and pci-to-pci bridge specs, which seems useful to
me.  However, I still cannot find pcie-to-pci bridge spec online (as
you have mentioned above).  Is that only for registered users?

-- peterx

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