From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42261) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZEZ0D-0000n8-RO for qemu-devel@nongnu.org; Mon, 13 Jul 2015 04:22:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZEZ09-0003YA-Sn for qemu-devel@nongnu.org; Mon, 13 Jul 2015 04:22:17 -0400 Date: Mon, 13 Jul 2015 11:22:09 +0300 From: "Michael S. Tsirkin" Message-ID: <20150713112041-mutt-send-email-mst@redhat.com> References: <1436766411-29144-1-git-send-email-jasowang@redhat.com> <1436766411-29144-5-git-send-email-jasowang@redhat.com> <20150713102402-mutt-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150713102402-mutt-send-email-mst@redhat.com> Subject: Re: [Qemu-devel] [PATCH 5/5] virtio-net: unbreak any layout List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jason Wang Cc: clg@fr.ibm.com, qemu-devel@nongnu.org, Greg Kurz , qemu-stable@nongnu.org On Mon, Jul 13, 2015 at 10:24:59AM +0300, Michael S. Tsirkin wrote: > On Mon, Jul 13, 2015 at 01:46:51PM +0800, Jason Wang wrote: > > Commit 032a74a1c0fcdd5fd1c69e56126b4c857ee36611 > > ("virtio-net: byteswap virtio-net header") breaks any layout by > > requiring out_sg[0].iov_len >= n->guest_hdr_len. Fixing this by > > copying header to temporary buffer and copying it back after byteswap. > > > > Fixes 032a74a1c0fcdd5fd1c69e56126b4c857ee36611 > > ("virtio-net: byteswap virtio-net header") > > Cc: qemu-stable@nongnu.org > > Cc: clg@fr.ibm.com > > Signed-off-by: Jason Wang > > --- > > hw/net/virtio-net.c | 10 +++++++--- > > 1 file changed, 7 insertions(+), 3 deletions(-) > > > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > > index e3c2db3..b42af8f 100644 > > --- a/hw/net/virtio-net.c > > +++ b/hw/net/virtio-net.c > > @@ -1139,10 +1139,11 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q) > > } > > > > while (virtqueue_pop(q->tx_vq, &elem)) { > > - ssize_t ret, len; > > + ssize_t ret, len, s; > > unsigned int out_num = elem.out_num; > > struct iovec *out_sg = &elem.out_sg[0]; > > struct iovec sg[VIRTQUEUE_MAX_SIZE]; > > + struct virtio_net_hdr hdr; > > > > if (out_num < 1) { > > error_report("virtio-net header not in first element"); > > @@ -1150,11 +1151,14 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q) > > } > > > > if (n->has_vnet_hdr) { > > - if (out_sg[0].iov_len < n->guest_hdr_len) { > > + s = iov_to_buf(out_sg, out_num, 0, &hdr, sizeof(hdr)); > > + if (s != sizeof(hdr)) { > > error_report("virtio-net header incorrect"); > > exit(1); > > } > > - virtio_net_hdr_swap(vdev, (void *) out_sg[0].iov_base); > > + virtio_net_hdr_swap(vdev, (void *) &hdr); > > + s = iov_from_buf(out_sg, out_num, 0, &hdr, sizeof(hdr)); > > + assert(s == sizeof(hdr)); > > } > > > > /* > > Looks like this will write into out_sg - that's violating the virtio spec. And the fault lies with the original code upstream - not with these patches. In my opinion the thing to do here is to completely avoid using vnet header for cross endian unless host supports ioctls to set endian-ness. > > -- > > 2.1.4