From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH RFC] pass write value to in_range pointers Date: Tue, 23 Jun 2009 12:52:21 +0300 Message-ID: <4A40A5D5.4080208@redhat.com> References: <20090619002224.15859.97977.stgit@dev.haskins.net> <20090619003045.15859.73197.stgit@dev.haskins.net> <20090622151631.GA14780@redhat.com> <4A3FA6FC.9030301@novell.com> <20090622160833.GA15228@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gregory Haskins , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mtosatti@redhat.com, paulmck@linux.vnet.ibm.com, markmc@redhat.com To: "Michael S. Tsirkin" Return-path: Received: from mx2.redhat.com ([66.187.237.31]:38923 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751729AbZFWJv0 (ORCPT ); Tue, 23 Jun 2009 05:51:26 -0400 In-Reply-To: <20090622160833.GA15228@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 06/22/2009 07:08 PM, Michael S. Tsirkin wrote: > On Mon, Jun 22, 2009 at 11:45:00AM -0400, Gregory Haskins wrote: > >> Michael S. Tsirkin wrote: >> >>> It seems that a lot of complexity and trickiness with iosignalfd is >>> handling the group/item relationship, which comes about because kvm does >>> not currently let a device on the bus claim a write transaction based on the >>> value written. This could be greatly simplified if the value written >>> was passed to the in_range check for write operation. We could then >>> simply make each kvm_iosignalfd a device on the bus. >>> >>> What does everyone think of the following lightly tested patch? >>> >>> >> Hi Michael, >> Its interesting, but I am not convinced its necessary. We created the >> group/item layout because iosignalfds are unique in that they are >> probably the only IO device that wants to do some kind of address >> aliasing. >> > > We actually already have aliasing: is_write flag is used for this > purpose. Actually, it's possible to remove is_write by passing > a null pointer in write_val for reads. I like this a bit less as > the code generated is less compact ... Avi, what do you think? > Greg, won't Michael's patch eliminate a big chunk from your iosignalfd patches? Seems like a win to me. > One is enough :) > Seriously, do you see that this saves you all of RCU, linked lists and > counters? You don't need to keep track of iofds, you don't need to > implement your own lookup logic - you just use the kvm device > and that's it. > > Yup. -- error compiling committee.c: too many arguments to function