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 389DCC3279B for ; Tue, 10 Jul 2018 05:50:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9744920881 for ; Tue, 10 Jul 2018 05:50:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9744920881 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 S1751263AbeGJFuN (ORCPT ); Tue, 10 Jul 2018 01:50:13 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:39444 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751005AbeGJFuL (ORCPT ); Tue, 10 Jul 2018 01:50:11 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 170C3402312B; Tue, 10 Jul 2018 05:50:11 +0000 (UTC) Received: from [10.72.12.151] (ovpn-12-151.pek2.redhat.com [10.72.12.151]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 676612026D6B; Tue, 10 Jul 2018 05:50:06 +0000 (UTC) Subject: Re: [PATCH net-next v1 4/5] virtio_ring: add event idx support in packed ring To: Tiwei Bie , mst@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, virtio-dev@lists.oasis-open.org Cc: wexu@redhat.com, jfreimann@redhat.com References: <20180709072241.8886-1-tiwei.bie@intel.com> <20180709072241.8886-5-tiwei.bie@intel.com> From: Jason Wang Message-ID: <9ee31221-9f4a-f1c5-0f0b-8d178bb536e9@redhat.com> Date: Tue, 10 Jul 2018 13:50:03 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180709072241.8886-5-tiwei.bie@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Tue, 10 Jul 2018 05:50:11 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Tue, 10 Jul 2018 05:50:11 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'jasowang@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018年07月09日 15:22, Tiwei Bie wrote: > @@ -1059,9 +1059,19 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > * suppressions. */ > virtio_mb(vq->weak_barriers); > > + old = vq->next_avail_idx - vq->num_added; > + new = vq->next_avail_idx; > + vq->num_added = 0; > + > snapshot = *(u32 *)vq->vring_packed.device; I think we should use READ_ONCE() to prevent compiler from re-reading. > + off_wrap = virtio16_to_cpu(_vq->vdev, (__virtio16)(snapshot & 0xffff)); > flags = virtio16_to_cpu(_vq->vdev, (__virtio16)(snapshot >> 16)) & 0x3; > > + wrap_counter = off_wrap >> 15; > + event_idx = off_wrap & ~(1 << 15); > + if (wrap_counter != vq->avail_wrap_counter) > + event_idx -= vq->vring_packed.num; Thanks