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Re: [Xen-devel] Virtualization project idea

To: admin@xxxxxxxxxxx
Subject: Re: [Xen-devel] Virtualization project idea
From: Dhananjay Goel <dhananjaygoel123@xxxxxxxxx>
Date: Fri, 27 Aug 2010 15:26:23 +0530
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, James Harper <james.harper@xxxxxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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Might be we can do it such that a file being accessed from USB has a lock in a VM and release once we're done with the file. So, only one VM (at a time) will have control on a file in USB device. 


On Fri, Aug 27, 2010 at 3:20 PM, David Markey <admin@xxxxxxxxxxx> wrote:
I dont think so, I'm not sure there is anything in the USB protocol that would allow this.

You would have to somehow have a lock, and allow only one VM access at a time.

On 27 August 2010 10:48, Dhananjay Goel <dhananjaygoel123@xxxxxxxxx> wrote:
On Fri, Aug 27, 2010 at 3:14 PM, Keir Fraser <keir.fraser@xxxxxxxxxxxxx> wrote:
On 27/08/2010 10:25, "Dhananjay Goel" <dhananjaygoel123@xxxxxxxxx> wrote:

>  Would USB over IP not be helpful here?
> USB over IP is just another way of doing direct USB passthru,
> it doesn't really allow sharing the devices.
> --Consider a use case: You are using your mobile for browsing internet on PC.
> Your mobile device 
> acts a usb modem for the host machine. That can not be used in guest
> for internet connectivity simuntaneously. You need to connect/disconnect
> every time to access internet whereas it would have been seamless
> internet connectivity. 

You don't necessarily share network, disc, or mouse/keyboard at the USB
level. For network, as an example, the hardware device belongs to the host
which provides NATed or bridged networking to VMs. VMs see a virtual network
device rather than the underlying physical device. Similar principle applies
to other device classes -- VMs see a virtual device. If you want a VM to see
a property of a physical device that cannot be expressed in your virtual
device model, you pass that physical device through directly to that one VM.
If you want direct passthrough and some semblance of sharing between VMs...
that's harder to do.

I agree its difficult to do. But is it possible to do? Can we make such that USB devices are shared across VMs? Any suggestion of how it can be done? 

 -- Keir

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