From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-dev-return-5151-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 99650984027 for ; Sun, 9 Dec 2018 14:33:49 +0000 (UTC) Date: Sun, 9 Dec 2018 09:33:42 -0500 From: "Michael S. Tsirkin" 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> Subject: [virtio-dev] Re: [RFC 3/3] virtio_ring: use new vring flags 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 List-ID: 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 --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org