From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH 0/5] Various USB fixes and improvements Date: Thu, 14 Aug 2008 12:55:54 -0500 Message-ID: <48A471AA.2010001@codemonkey.ws> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org To: Max Krasnyansky Return-path: Received: from wr-out-0506.google.com ([64.233.184.238]:30080 "EHLO wr-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759224AbYHNR4e (ORCPT ); Thu, 14 Aug 2008 13:56:34 -0400 Received: by wr-out-0506.google.com with SMTP id 69so641675wri.5 for ; Thu, 14 Aug 2008 10:56:33 -0700 (PDT) In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: Max Krasnyansky wrote: > This patch series started when I tried to share USB ports between > four instances of Windows XP running on the same Linux box (under KVM). > I quickly realized that current USB support is not very flexible. We do > not handle devices disconnects, there is not way to assign certain USB > ports to VM instance, etc. > > Once I fixed that I discovered that USB devices that I absolutely need > in the VMs (Xilinx and Altera USB dongles) do not really work with > QEMU. VMs were getting stuck, applications unhappy, etc. > So I endded up rewriting UHCI and Linux host USB layers to make them > fully async and to support multiple outstanding transactions. > > The result is quite nice. We can now assign USB buses to VM instances > and devices are automatically connected to the VMs. Just do > usb_add host:N.* > in the console or -usbdevice command line option (N is the bus number). > Also when device is disconnected from the host it's automatically removed > from the guest. > > Host USB devices operate in fully async mode (except the control transfers). > All the stalls and jerkiness due to long synchronous transactions is gone. > I can easily hook up four different USB devices (mouse, CF card reader, > phone, Xilinx dongle) and everything is working perfectly. Mouse movements > are silky smooth :). > > I did some profiling with OProfile and we seems to be doing ok while XP is > pumping ~10 MBytes over USB (reported by one of the apps I'm using). UHCI > stuff is well below VNC for example. > > There is more work to be done (async control transfers for example). But I > think this is way better than what we have now and is ready for more testing > by wider audience. > > Most of the testing so far was done with KVM flavor of QEMU. I did test > generic i386-softmmu target a bit, it's too slow for any serious testing > with XP. I did full compile (all targets) too and it went fine. > Altogether this patch series looks very promising. The current USB pass through code is pretty fickle so some clean-up is definitely needed. I don't understand USB well enough to do a thorough review. I hope others can look through it and provide more detailed feedback. I'll do some testing of it tonight. Regards, Anthony Liguori