From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:38528) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ShBy0-0000Rd-Pm for qemu-devel@nongnu.org; Tue, 19 Jun 2012 23:52:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ShBxz-0006Rb-5I for qemu-devel@nongnu.org; Tue, 19 Jun 2012 23:52:28 -0400 Received: from gate.crashing.org ([63.228.1.57]:54291) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ShBxy-0006R6-Sh for qemu-devel@nongnu.org; Tue, 19 Jun 2012 23:52:27 -0400 Message-ID: <1340164332.28143.66.camel@pasglop> From: Benjamin Herrenschmidt Date: Wed, 20 Jun 2012 13:52:12 +1000 In-Reply-To: <20120620031421.GB9144@truffala.fritz.box> References: <1340087992-2399-1-git-send-email-benh@kernel.crashing.org> <1340087992-2399-8-git-send-email-benh@kernel.crashing.org> <4FE081CE.1060001@redhat.com> <1340137438.28143.28.camel@pasglop> <20120620031421.GB9144@truffala.fritz.box> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 07/13] usb: Convert usb_packet_{map, unmap} to universal DMA helpers List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson Cc: Gerd Hoffmann , anthony@codemonkey.ws, qemu-devel@nongnu.org On Wed, 2012-06-20 at 13:14 +1000, David Gibson wrote: > So, in fact the original comment is a bit out of date. With the > current version of this series, then a guest attempt to invalidate > will be delayed until the unmap occurs. No, this code was dropped, including the tracking of the maps, following comments from Anthony and others. The API for providing a cancel callback is still there but nothing will call it unless the backend does its own tracking and decides to do so. As it is, the race exist but: - It will only hurt the guest - And only for a very buggy guest So the worst case is that it hurts something like kdump. I plan to re-introduce some of the mechanisms for cancellation eventually, but we agreed that it wasn't going to be a show stopper and that we could work on getting that sorted in a second phase. I'm looking at a more efficient way to deal with the tracking of the maps as well since some devices uses them often. Cheers, Ben.