From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:34938) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TXs1e-0007GE-RG for qemu-devel@nongnu.org; Mon, 12 Nov 2012 06:18:01 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TXs1b-0008Fe-PK for qemu-devel@nongnu.org; Mon, 12 Nov 2012 06:17:58 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36184) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TXs1b-0008FS-HL for qemu-devel@nongnu.org; Mon, 12 Nov 2012 06:17:55 -0500 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id qACBHsUt025324 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 12 Nov 2012 06:17:54 -0500 Message-ID: <50A0DB54.1060007@redhat.com> Date: Mon, 12 Nov 2012 12:19:48 +0100 From: Hans de Goede MIME-Version: 1.0 References: <1352210901-1923-1-git-send-email-hdegoede@redhat.com> <1352210901-1923-9-git-send-email-hdegoede@redhat.com> <509BD18A.7070709@redhat.com> In-Reply-To: <509BD18A.7070709@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 8/8] usb-hid: Allow connecting to a USB-2 device List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gerd Hoffmann Cc: qemu-devel@nongnu.org Hi, On 11/08/2012 04:36 PM, Gerd Hoffmann wrote: > On 11/06/12 15:08, Hans de Goede wrote: >> Our ehci code has is capable of significantly lowering the wakeup rate >> for the hcd emulation while the device is idle. It is possible to add >> similar code ot the uhci emulation, but that simply is not there atm, >> and there is no reason why a (virtual) usb device can not be a USB-2 device. > > We should probably add usb-tablet2 (+friends) devices as this is a > guest-visible change. We could also try tricks with properties but I > guess separate devices are easier. A quick status update on this patchset. a) I promised to resend it without this patch Friday afternoon at kvm-forum, which I went to do directly after saying goodbye, but when I unsuspended my laptop it broke... (looks like the cable between the motherboard and screen has a loose contact), so it got delayed a bit. b) While working on fixing all the comments on the set yesterday to send a v2, I realized at the very last moment that handling interrupts packet async, rather then by nakking them, causes problems with migration, as the following can happen: 1) hcd submits a packet to device, device returns USB_RET_ASYNC 2) device gets some data, fills the packet, calls complete() on it 3) For ehci complete() calls a bh, which immediately walks the async schedule, but if not enough time has passed since the last bh, to process periodic frames, or if the interrupt endpoint has an interval of more then 1 ms, and this periodic frame it is not scheduled, the completion will not get written back to guest memory! 4) If we now migrate, the completion never gets written back to guest memory and the interrupt packet is effectively lost Notice that the same can happen with non async interrupt packets on the uhci code... I was planning on modifying that to be more like the ehci code anyways to lower the CPU-load (amount of wakeups), but that will not necessarily fix this, so this needs some more thinking. I hope to have a v2 of the wakeup reduction for interrupt endpoints patchset by the end of the day ... Regards, Hans