From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06871ECDE42 for ; Thu, 18 Oct 2018 02:44:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B252F2083A for ; Thu, 18 Oct 2018 02:44:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B252F2083A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727466AbeJRKnb (ORCPT ); Thu, 18 Oct 2018 06:43:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48030 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727267AbeJRKnb (ORCPT ); Thu, 18 Oct 2018 06:43:31 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 69C40C03D466; Thu, 18 Oct 2018 02:44:50 +0000 (UTC) Received: from [10.72.12.103] (ovpn-12-103.pek2.redhat.com [10.72.12.103]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2A2651062243; Thu, 18 Oct 2018 02:44:38 +0000 (UTC) Subject: Re: [PATCH net-next V2 6/8] vhost: packed ring support To: "Michael S. Tsirkin" Cc: Tiwei Bie , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, wexu@redhat.com, jfreimann@redhat.com, maxime.coquelin@redhat.com References: <1531711691-6769-1-git-send-email-jasowang@redhat.com> <1531711691-6769-7-git-send-email-jasowang@redhat.com> <20181012143244.GA28400@debian> <20181012131812-mutt-send-email-mst@kernel.org> <447f47fa-32dd-a408-dd81-13a9839e0748@redhat.com> <20181014224208-mutt-send-email-mst@kernel.org> <20181015062241-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: Date: Thu, 18 Oct 2018 10:44:36 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181015062241-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Thu, 18 Oct 2018 02:44:50 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/10/15 下午6:25, Michael S. Tsirkin wrote: > On Mon, Oct 15, 2018 at 10:51:06AM +0800, Jason Wang wrote: >> On 2018年10月15日 10:43, Michael S. Tsirkin wrote: >>> On Mon, Oct 15, 2018 at 10:22:33AM +0800, Jason Wang wrote: >>>> On 2018年10月13日 01:23, Michael S. Tsirkin wrote: >>>>> On Fri, Oct 12, 2018 at 10:32:44PM +0800, Tiwei Bie wrote: >>>>>> On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote: >>>>>> [...] >>>>>>> @@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg >>>>>>> vq->last_avail_idx = s.num; >>>>>>> /* Forget the cached index value. */ >>>>>>> vq->avail_idx = vq->last_avail_idx; >>>>>>> + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) { >>>>>>> + vq->last_avail_wrap_counter = wrap_counter; >>>>>>> + vq->avail_wrap_counter = vq->last_avail_wrap_counter; >>>>>>> + } >>>>>>> break; >>>>>>> case VHOST_GET_VRING_BASE: >>>>>>> s.index = idx; >>>>>>> s.num = vq->last_avail_idx; >>>>>>> + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) >>>>>>> + s.num |= vq->last_avail_wrap_counter << 31; >>>>>>> + if (copy_to_user(argp, &s, sizeof(s))) >>>>>>> + r = -EFAULT; >>>>>>> + break; >>>>>>> + case VHOST_SET_VRING_USED_BASE: >>>>>>> + /* Moving base with an active backend? >>>>>>> + * You don't want to do that. >>>>>>> + */ >>>>>>> + if (vq->private_data) { >>>>>>> + r = -EBUSY; >>>>>>> + break; >>>>>>> + } >>>>>>> + if (copy_from_user(&s, argp, sizeof(s))) { >>>>>>> + r = -EFAULT; >>>>>>> + break; >>>>>>> + } >>>>>>> + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) { >>>>>>> + wrap_counter = s.num >> 31; >>>>>>> + s.num &= ~(1 << 31); >>>>>>> + } >>>>>>> + if (s.num > 0xffff) { >>>>>>> + r = -EINVAL; >>>>>>> + break; >>>>>>> + } >>>>>> Do we want to put wrap_counter at bit 15? >>>>> I think I second that - seems to be consistent with >>>>> e.g. event suppression structure and the proposed >>>>> extension to driver notifications. >>>> Ok, I assumes packed virtqueue support 64K but looks not. I can change it to >>>> bit 15 and GET_VRING_BASE need to be changed as well. >>>> >>>>>> If put wrap_counter at bit 31, the check (s.num > 0xffff) >>>>>> won't be able to catch the illegal index 0x8000~0xffff for >>>>>> packed ring. >>>>>> >>>> Do we need to clarify this in the spec? >>> Isn't this all internal vhost stuff? >> I meant the illegal index 0x8000-0xffff. > It does say packed virtqueues support up to 2 15 entries each. > > But yes we can add a requirement that devices do not expose > larger rings. Split does not support 2**16 either, right? > With 2**16 enties avail index becomes 0 and ring looks empty. > Yes, so it's better to clarify this in the spec. Thanks