On Mon, Mar 23, 2026 at 03:31:49PM +0100, Laurent Vivier wrote: > udp_vu_sock_recv() currently mixes two concerns: receiving data from the > socket and managing virtqueue buffers (collecting, rewinding, releasing). > This makes the function harder to reason about and couples socket I/O > with virtqueue state. > > Move all virtqueue operations, vu_collect(), vu_init_elem(), > vu_queue_rewind(), vu_set_vnethdr(), and the queue-readiness check, into > udp_vu_sock_to_tap(), which is the only caller. This turns > udp_vu_sock_recv() into a pure socket receive function that simply reads > into the provided iov array and adjusts its length. > > Signed-off-by: Laurent Vivier Reviewed-by: David Gibson > --- > udp_vu.c | 110 +++++++++++++++++++++++++------------------------------ > 1 file changed, 49 insertions(+), 61 deletions(-) > > diff --git a/udp_vu.c b/udp_vu.c > index 6638cb0ddc5f..dc949e30a793 100644 > --- a/udp_vu.c > +++ b/udp_vu.c > @@ -33,9 +33,6 @@ > #include "udp_vu.h" > #include "vu_common.h" > > -static struct iovec iov_vu [VIRTQUEUE_MAX_SIZE]; > -static struct vu_virtq_element elem [VIRTQUEUE_MAX_SIZE]; > - > /** > * udp_vu_hdrlen() - Sum size of all headers, from UDP to virtio-net > * @v6: Set for IPv6 packet > @@ -58,78 +55,35 @@ static size_t udp_vu_hdrlen(bool v6) > > /** > * udp_vu_sock_recv() - Receive datagrams from socket into vhost-user buffers > - * @c: Execution context > * @iov: IO vector for the frame (in/out) > * @cnt: Number of IO vector entries (in/out) > - * @vq: virtqueue to use to receive data > * @s: Socket to receive from > * @v6: Set for IPv6 connections > * > - * Return: size of received data, 0 if the datagram > - * was discarded because the virtqueue is not ready, -1 on error > + * Return: size of received data, -1 on error > */ > -static ssize_t udp_vu_sock_recv(const struct ctx *c, struct iovec *iov, > - size_t *cnt, unsigned *elem_used, > - struct vu_virtq *vq, int s, bool v6) > +static ssize_t udp_vu_sock_recv(struct iovec *iov, size_t *cnt, int s, bool v6) > { > - const struct vu_dev *vdev = c->vdev; > - struct msghdr msg = { 0 }; > + struct iovec msg_iov[*cnt]; > + struct msghdr msg = { 0 }; > struct iov_tail payload; > - size_t hdrlen, iov_used; > - unsigned elem_cnt; > - unsigned i, j; > + size_t hdrlen; > ssize_t dlen; > > - assert(!c->no_udp); > - > - if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) { > - debug("Got UDP packet, but RX virtqueue not usable yet"); > - > - if (recvmsg(s, &msg, MSG_DONTWAIT) < 0) > - debug_perror("Failed to discard datagram"); > - > - *cnt = 0; > - return 0; > - } > - > /* compute L2 header length */ > hdrlen = udp_vu_hdrlen(v6); > > - elem_cnt = vu_collect(vdev, vq, elem, ARRAY_SIZE(elem), > - iov, *cnt, &iov_used, > - IP_MAX_MTU + ETH_HLEN + VNET_HLEN, NULL); > - if (elem_cnt == 0) > - return -1; > - > - assert((size_t)elem_cnt == iov_used); /* one iovec per element */ > - > - payload = IOV_TAIL(iov, iov_used, hdrlen); > + payload = IOV_TAIL(iov, *cnt, hdrlen); > > - struct iovec msg_iov[payload.cnt]; > msg.msg_iov = msg_iov; > msg.msg_iovlen = iov_tail_clone(msg.msg_iov, payload.cnt, &payload); > > /* read data from the socket */ > dlen = recvmsg(s, &msg, 0); > - if (dlen < 0) { > - vu_queue_rewind(vq, elem_cnt); > + if (dlen < 0) > return -1; > - } > - > - *cnt = vu_pad(iov, iov_used, 0, dlen + hdrlen); > - > - *elem_used = 0; > - for (i = 0, j = 0; j < *cnt && i < elem_cnt; i++) { > - if (j + elem[i].in_num > *cnt) > - elem[i].in_num = *cnt - j; > - j += elem[i].in_num; > - (*elem_used)++; > - } > > - vu_set_vnethdr(iov[0].iov_base, *elem_used); > - > - /* release unused buffers */ > - vu_queue_rewind(vq, elem_cnt - *elem_used); > + *cnt = vu_pad(iov, *cnt, 0, dlen + hdrlen); > > return dlen; > } > @@ -217,26 +171,60 @@ static void udp_vu_csum(const struct flowside *toside, > */ > void udp_vu_sock_to_tap(const struct ctx *c, int s, int n, flow_sidx_t tosidx) > { > + static struct iovec iov_vu [VIRTQUEUE_MAX_SIZE]; > + static struct vu_virtq_element elem [VIRTQUEUE_MAX_SIZE]; > const struct flowside *toside = flowside_at_sidx(tosidx); > bool v6 = !(inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr)); > struct vu_dev *vdev = c->vdev; > struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE]; > - struct iov_tail data; > int i; > > + assert(!c->no_udp); > + > + if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) { > + struct msghdr msg = { 0 }; > + > + debug("Got UDP packet, but RX virtqueue not usable yet"); > + > + for (i = 0; i < n; i++) { > + if (recvmsg(s, &msg, MSG_DONTWAIT) < 0) > + debug_perror("Failed to discard datagram"); > + } > + > + return; > + } > + > for (i = 0; i < n; i++) { > - unsigned elem_used; > + unsigned elem_used, elem_cnt, j, k; > size_t iov_cnt; > ssize_t dlen; > > - iov_cnt = ARRAY_SIZE(iov_vu); > - dlen = udp_vu_sock_recv(c, iov_vu, &iov_cnt, &elem_used, vq, > - s, v6); > - if (dlen < 0) > + elem_cnt = vu_collect(vdev, vq, elem, ARRAY_SIZE(elem), > + iov_vu, ARRAY_SIZE(iov_vu), &iov_cnt, > + IP_MAX_MTU + ETH_HLEN + VNET_HLEN, NULL); > + if (elem_cnt == 0) > + break; > + > + dlen = udp_vu_sock_recv(iov_vu, &iov_cnt, s, v6); > + if (dlen < 0) { > + vu_queue_rewind(vq, elem_cnt); > break; > + } > + > + elem_used = 0; > + for (j = 0, k = 0; k < iov_cnt && j < elem_cnt; j++) { > + if (k + elem[j].in_num > iov_cnt) > + elem[j].in_num = iov_cnt - k; > + k += elem[j].in_num; > + elem_used++; > + } > + > + /* release unused buffers */ > + vu_queue_rewind(vq, elem_cnt - elem_used); > > if (iov_cnt > 0) { > - data = IOV_TAIL(iov_vu, iov_cnt, 0); > + struct iov_tail data = IOV_TAIL(iov_vu, iov_cnt, 0); > + vu_set_vnethdr(iov_vu[0].iov_base, elem_used); > udp_vu_prepare(c, &data, toside, dlen); > if (*c->pcap) { > udp_vu_csum(toside, &data); > -- > 2.53.0 > -- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson