From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:34546) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gvzkF-0005IU-Oh for qemu-devel@nongnu.org; Tue, 19 Feb 2019 02:23:12 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gvzkF-0003x6-1n for qemu-devel@nongnu.org; Tue, 19 Feb 2019 02:23:11 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36184) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gvzkE-0003wh-RF for qemu-devel@nongnu.org; Tue, 19 Feb 2019 02:23:10 -0500 References: <1550118402-4057-1-git-send-email-wexu@redhat.com> <1550118402-4057-10-git-send-email-wexu@redhat.com> From: Jason Wang Message-ID: <1c16f234-af83-23c8-2194-94be63574299@redhat.com> Date: Tue, 19 Feb 2019 15:23:01 +0800 MIME-Version: 1.0 In-Reply-To: <1550118402-4057-10-git-send-email-wexu@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v4 09/11] virtio-net: update the head descriptor in a chain lastly List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: wexu@redhat.com, qemu-devel@nongnu.org Cc: mst@redhat.com, jfreiman@redhat.com, maxime.coquelin@redhat.com, tiwei.bie@intel.com On 2019/2/14 =E4=B8=8B=E5=8D=8812:26, wexu@redhat.com wrote: > From: Wei Xu > > This is a helper for packed ring. > > To support packed ring, the head descriptor in a chain should be update= d > lastly since no 'avail_idx' like in packed ring to explicitly tell the > driver side that all payload is ready after having done the chain, so > the head is always visible immediately. > > This patch fills the header after done all the other ones. > > Signed-off-by: Wei Xu It's really odd to workaround API issue in the implementation of device.=20 Please introduce batched used updating helpers instead. Thanks > --- > hw/net/virtio-net.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > index 3f319ef..330abea 100644 > --- a/hw/net/virtio-net.c > +++ b/hw/net/virtio-net.c > @@ -1251,6 +1251,8 @@ static ssize_t virtio_net_receive_rcu(NetClientSt= ate *nc, const uint8_t *buf, > struct virtio_net_hdr_mrg_rxbuf mhdr; > unsigned mhdr_cnt =3D 0; > size_t offset, i, guest_offset; > + VirtQueueElement head; > + int head_len =3D 0; > =20 > if (!virtio_net_can_receive(nc)) { > return -1; > @@ -1328,7 +1330,13 @@ static ssize_t virtio_net_receive_rcu(NetClientS= tate *nc, const uint8_t *buf, > } > =20 > /* signal other side */ > - virtqueue_fill(q->rx_vq, elem, total, i++); > + if (i =3D=3D 0) { > + head_len =3D total; > + head =3D *elem; > + } else { > + virtqueue_fill(q->rx_vq, elem, len, i); > + } > + i++; > g_free(elem); > } > =20 > @@ -1339,6 +1347,7 @@ static ssize_t virtio_net_receive_rcu(NetClientSt= ate *nc, const uint8_t *buf, > &mhdr.num_buffers, sizeof mhdr.num_buffers); > } > =20 > + virtqueue_fill(q->rx_vq, &head, head_len, 0); > virtqueue_flush(q->rx_vq, i); > virtio_notify(vdev, q->rx_vq); > =20