From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758981AbbCDPbj (ORCPT ); Wed, 4 Mar 2015 10:31:39 -0500 Received: from cantor2.suse.de ([195.135.220.15]:60081 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758542AbbCDPbi (ORCPT ); Wed, 4 Mar 2015 10:31:38 -0500 Message-ID: <54F72555.30304@suse.com> Date: Wed, 04 Mar 2015 16:31:33 +0100 From: Juergen Gross User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Greg KH CC: David Vrabel , linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, linux-usb@vger.kernel.org, cyliu@suse.com Subject: Re: [Xen-devel] [PATCH 3/4] usb: Introduce Xen pvUSB backend References: <1424957717-392-1-git-send-email-jgross@suse.com> <1424957717-392-4-git-send-email-jgross@suse.com> <54F44BD5.1030008@citrix.com> <54F7091C.1050001@suse.com> <20150304152722.GA11839@kroah.com> In-Reply-To: <20150304152722.GA11839@kroah.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/04/2015 04:27 PM, Greg KH wrote: > On Wed, Mar 04, 2015 at 02:31:08PM +0100, Juergen Gross wrote: >> On 03/02/2015 12:39 PM, David Vrabel wrote: >>> On 26/02/15 13:35, Juergen Gross wrote: >>>> Introduces the Xen pvUSB backend. With pvUSB it is possible for a Xen >>>> domU to communicate with a USB device assigned to that domU. The >>>> communication is all done via the pvUSB backend in a driver domain >>>> (usually Dom0) which is owner of the physical device. >>> >>> Why do we need a kernel usb backend instead of a user-space one using >>> libusb? >> >> Good question. At a first glance libusb seems to offer most/all needed >> interfaces. The main question is whether performance with libusb will >> be okay. There will be one additional copy of the I/O data needed if >> I've read the code in drivers/usb/core/devio.c correctly. > > You can drive USB devices at line speed using libusb just fine. Try it > out and see please, processors copy data _very_ fast these days. Okay, thanks for the information. I'll take this as a hint to try the user space variant. :-) Juergen