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Re: [Qemu-devel] [RFC] pxb: Restrict to x86

From: Marcel Apfelbaum
Subject: Re: [Qemu-devel] [RFC] pxb: Restrict to x86
Date: Sun, 8 Jan 2017 10:17:12 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1

On 01/06/2017 09:41 PM, Michael S. Tsirkin wrote:
On Fri, Jan 06, 2017 at 08:13:11AM +0200, Marcel Apfelbaum wrote:
On 01/06/2017 07:04 AM, David Gibson wrote:
The PCI Expander Bridge (PXB) device is essentially a hack to allow
different PCIe devices to be assigned to different NUMA nodes on x86.  Each
PXB is sort-of a separate PCI host bridge, except that its config space
is shared with the config space of the main PCI host bridge, rather than
being independent.

Hi David,

This is only necessary if the platform doesn't (easily) allow truly
independent PCI host bridges.  AFAIK that's just x86.

Indeed, it is possible to support independent PCI host bridges on x86 by
using a separate MMCONFIG space for each one and enable separate PCI domains.
We simply didn't need this until now, but maybe will be implemented it in the 

In fact I would say that's the cleanest way to do this on q35.

Message received :)


This patch makes it possible to configure PXB out of the build, and adjusts
the default configs so it's only included on x86 targets.


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