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RE: [Xen-devel] [Q] Is qemu used when we use VTd?

To: "Akio Takebe" <takebe_akio@xxxxxxxxxxxxxx>, "Jean Guyader" <jean.guyader@xxxxxxxxx>
Subject: RE: [Xen-devel] [Q] Is qemu used when we use VTd?
From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Date: Fri, 12 Sep 2008 10:46:31 +0800
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Thread-topic: [Xen-devel] [Q] Is qemu used when we use VTd?
>From: Akio Takebe
>Sent: 2008年9月11日 19:48
>Can we directly use MMCONFIG for PCI-Express card 
>pass-throughed by VT-d on HVM?

You can't. MMCONFIG in no sense vary from old I/O port
style, as just a means to access PCI configuration space.
Note that PCI configuration space access has to be trapped
as it determines which devices, and also config space
content to be observed by HVM guest. Normally you'd need
some virtualization on config space content, such as BARs.
Thus even by presenting MMCONFIG capability to HVM
guest, you still need trap those access falling in that range.


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