From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753205Ab3AJIpE (ORCPT ); Thu, 10 Jan 2013 03:45:04 -0500 Received: from mail-we0-f173.google.com ([74.125.82.173]:48949 "EHLO mail-we0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751894Ab3AJIpB (ORCPT ); Thu, 10 Jan 2013 03:45:01 -0500 Message-ID: <50EE7F88.1010100@redhat.com> Date: Thu, 10 Jan 2013 09:44:56 +0100 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Rusty Russell CC: Jens Axboe , kvm@vger.kernel.org, linux-scsi@vger.kernel.org, mst@redhat.com, hutao@cn.fujitsu.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, stefanha@redhat.com Subject: Re: [PATCH v2 1/5] virtio: add functions for piecewise addition of buffers References: <1355833972-20319-1-git-send-email-pbonzini@redhat.com> <1355833972-20319-2-git-send-email-pbonzini@redhat.com> <87r4m45g88.fsf@rustcorp.com.au> <50E54DC0.4040609@redhat.com> <87pq1h508k.fsf@rustcorp.com.au> <50EADB62.1010704@redhat.com> <87wqvo3542.fsf@rustcorp.com.au> In-Reply-To: <87wqvo3542.fsf@rustcorp.com.au> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 08/01/2013 01:12, Rusty Russell ha scritto: >>>> >>> Unfortunately, that cannot work because not all architectures support >>>> >>> chained scatterlists. >>> >> >>> >> WHAT? I can't figure out what an arch needs to do to support this? >> > >> > It needs to use the iterator functions in its DMA driver. > But we don't care for virtio. True. >>> >> All archs we care about support them, though, so I think we can ignore >>> >> this issue for now. >> > >> > Kind of... In principle all QEMU-supported arches can use virtio, and >> > the speedup can be quite useful. And there is no Kconfig symbol for SG >> > chains that I can use to disable virtio-scsi on unsupported arches. :/ > Well, we #error if it's not supported. Then the lazy architectures can > fix it. Yeah, that would be one approach. But frankly, your patch is really disgusting. :) Not your fault, of course, but I still prefer a limited amount of duplication. Perhaps we can get the best of both worlds, I'll take a look when I have some time. Paolo