From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758922AbbCDP10 (ORCPT ); Wed, 4 Mar 2015 10:27:26 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:52883 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758433AbbCDP1Y (ORCPT ); Wed, 4 Mar 2015 10:27:24 -0500 Date: Wed, 4 Mar 2015 07:27:22 -0800 From: Greg KH To: Juergen Gross 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 Message-ID: <20150304152722.GA11839@kroah.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54F7091C.1050001@suse.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. thanks, greg k-h