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Re: [Xen-users] [XEN 3.3 - PCI passthrough] - interaction latencies with

To: jer jer <jeremie.garcia.trash@xxxxxxxxx>
Subject: Re: [Xen-users] [XEN 3.3 - PCI passthrough] - interaction latencies with /dev/ttyUSB0
From: Ken Cobler <kcobler@xxxxxxxxxxxxxx>
Date: Mon, 12 Jan 2009 07:16:27 -0600
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jer jer wrote:
Thanks for your help Ken,

I'm gonna have a look to the USB over IP solution.
Nevertheless, in addition to my post, I ran further tests and noticed that when processing test on dom0 (no passthrough), everything works fine (no more latencies).
So, I'm about to conclude that the problem is due to PCI passthrough.
I'm a litlle bit surprised, cause I thought that doing this would have given direct USB access.

Is it known that pci passthrough pull down performances?

Furthertmore, I've read that XEN 3.4 will introduce virtualized USB driver. So can we concluide that no more support will be done on PCI passthrough?

Finally, do you have any perf issues running USB over IP?

Tks a lot!


It would be great to see complete USB virtualization in Xen. However, I don't think that would take away from PCI passthrough. Simply, there are other devices that are PCI devices and not USB, that could be passed to a domU.


With regards to USB over IP, I have only implemented a Digiboard hardware product called AnywhereUSB, http://www.digi.com/products/usb/anywhereusb.jsp

The only concern someone may have about AnywhereUSB is it will only support USB 1.0 speeds for all devices. In my application, that was not an issue.


Ken Cobler

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