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=-3.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 7C279C07E85 for ; Sun, 9 Dec 2018 14:33:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3D3A120672 for ; Sun, 9 Dec 2018 14:33:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3D3A120672 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 S1726279AbeLIOdt (ORCPT ); Sun, 9 Dec 2018 09:33:49 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47082 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726239AbeLIOds (ORCPT ); Sun, 9 Dec 2018 09:33:48 -0500 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 1CD57C028345; Sun, 9 Dec 2018 14:33:48 +0000 (UTC) Received: from redhat.com (ovpn-120-192.rdu2.redhat.com [10.10.120.192]) by smtp.corp.redhat.com (Postfix) with SMTP id EFE711019635; Sun, 9 Dec 2018 14:33:42 +0000 (UTC) Date: Sun, 9 Dec 2018 09:33:42 -0500 From: "Michael S. Tsirkin" To: Tiwei Bie Cc: jasowang@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, virtio-dev@lists.oasis-open.org, wexu@redhat.com, jfreimann@redhat.com, maxime.coquelin@redhat.com Subject: Re: [RFC 3/3] virtio_ring: use new vring flags Message-ID: <20181209093222-mutt-send-email-mst@kernel.org> References: <20181207084842.13133-1-tiwei.bie@intel.com> <20181207084842.13133-4-tiwei.bie@intel.com> <20181207130822-mutt-send-email-mst@kernel.org> <20181208134728.GC29772@dpdk-tbie> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181208134728.GC29772@dpdk-tbie> 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]); Sun, 09 Dec 2018 14:33:48 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Dec 08, 2018 at 09:47:29PM +0800, Tiwei Bie wrote: > On Fri, Dec 07, 2018 at 01:10:48PM -0500, Michael S. Tsirkin wrote: > > On Fri, Dec 07, 2018 at 04:48:42PM +0800, Tiwei Bie wrote: > > > Switch to using the _SPLIT_ and _PACKED_ variants of vring flags > > > in split ring and packed ring respectively. > > > > > > Signed-off-by: Tiwei Bie > > > --- > > > @@ -502,7 +505,8 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > > } > > > } > > > /* Last one doesn't continue. */ > > > - desc[prev].flags &= cpu_to_virtio16(_vq->vdev, ~VRING_DESC_F_NEXT); > > > + desc[prev].flags &= cpu_to_virtio16(_vq->vdev, > > > + (u16)~BIT(VRING_SPLIT_DESC_F_NEXT)); > > > > > > if (indirect) { > > > /* Now that the indirect table is filled in, map it. */ > > > > I kind of dislike it that this forces use of a cast here. > > Kind of makes it more fragile. Let's use a temporary instead? > > I tried something like this: > > u16 mask = ~BIT(VRING_SPLIT_DESC_F_NEXT); > > And it will still cause the warning: > > warning: large integer implicitly truncated to unsigned type [-Woverflow] > u16 mask = ~BIT(VRING_SPLIT_DESC_F_NEXT); > > If the cast isn't wanted, maybe use ~(1 << VRING_SPLIT_DESC_F_NEXT) > directly? What I'd like to see is a macro that warns/errors out if the shift is too large. I'll think it over on the weekend. > > > > > > -- > > > 2.17.1