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Re: [Xen-devel] Question: PV and HVM device list

To: Hu Jia Yi <jyhu@xxxxxxxxx>
Subject: Re: [Xen-devel] Question: PV and HVM device list
From: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
Date: Wed, 5 Sep 2007 16:42:39 +0100
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On Wed, Sep 05, 2007 at 02:13:58PM +0800, Hu Jia Yi wrote:
> I have two questions about xen. Hope I can find answers/hints in this
> mailing list.
> 1. how PV and HVM know about what physical devices are in the PC? 

They typically don't know anything about physical hardware. Normal practice
is to only assign virtual devices to guests - virtual network / disk or
sound & USB devices are most common (the latter two for HVM only).

> 2. If a USB disk is plugged in, how does xen notify this to PV and HVM
> so that the guest domains can do things as there were no virtualization
> layer.

Xen doesn't do anything when USB disks are plugged in. It is possible use
admin tools to explicitly map a USB disk through to a guest as a virtual
disk, or in HVM case to hand-off the entire USB device to the guest. This
is a manual admin config step though - nothing automatic occurrs.

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