> -----Original Message-----
> From: Xie, Huawei
> Sent: Tuesday, June 2, 2015 3:51 PM
> To: Ouyang, Changchun; dev at dpdk.org
> Cc: Cao, Waterman
> Subject: Re: [PATCH v3 1/4] lib_vhost: Fix enqueue/dequeue can't handle
> chained vring descriptors
>
> On 6/1/2015 4:26 PM, Ouyang, Changchun wrote:
> > Vring enqueue need consider the 2 cases:
> > 1. use separate descriptors to contain virtio header and actual data, e.g.
> the first descriptor
> > is for virtio header, and then followed by descriptors for actual data.
> > 2. virtio header and some data are put together in one descriptor, e.g. the
> first descriptor contain both
> > virtio header and part of actual data, and then followed by more
> descriptors for rest of packet data,
> > current DPDK based virtio-net pmd implementation is this case;
> >
> > So does vring dequeue, it should not assume vring descriptor is
> > chained or not chained, it should use
> > desc->flags to check whether it is chained or not. this patch also
> > desc->fixes TX corrupt issue in fedora 21
> > which uses one single vring descriptor(header and data are in one
> descriptor) for virtio tx process on default.
> Suggest remove fedora 21 in the commit message, at least the bug is related
> to virtio-net driver rather than distribution.
Just try to give more information that this patch can fix the issue TX corrupt
issue on fedora 21,
I don't think this information is contradict with what you mean.
> > Changes in v3
> > - support scattered mbuf, check the mbuf has 'next' pointer or not and
> copy all segments to vring buffer.
> >
> > Changes in v2
> > - drop the uncompleted packet
> > - refine code logic
> >
> > Signed-off-by: Changchun Ouyang <changchun.ouyang at intel.com>
> > ---
> > lib/librte_vhost/vhost_rxtx.c | 88
> > ++++++++++++++++++++++++++++++++++---------
> > 1 file changed, 71 insertions(+), 17 deletions(-)
> >
> > diff --git a/lib/librte_vhost/vhost_rxtx.c
> > b/lib/librte_vhost/vhost_rxtx.c index 4809d32..5fe1b6c 100644
> > --- a/lib/librte_vhost/vhost_rxtx.c
> > +++ b/lib/librte_vhost/vhost_rxtx.c
> > @@ -46,7 +46,8 @@
> > * This function adds buffers to the virtio devices RX virtqueue. Buffers
> > can
> > * be received from the physical port or from another virtio device. A
> packet
> > * count is returned to indicate the number of packets that are
> > succesfully
> > - * added to the RX queue. This function works when mergeable is disabled.
> > + * added to the RX queue. This function works when the mbuf is
> > + scattered, but
> > + * it doesn't support the mergeable feature.
> > */
> > static inline uint32_t __attribute__((always_inline))
> > virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id, @@ -59,7
> > +60,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
> > struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};
> > uint64_t buff_addr = 0;
> > uint64_t buff_hdr_addr = 0;
> > - uint32_t head[MAX_PKT_BURST], packet_len = 0;
> > + uint32_t head[MAX_PKT_BURST];
> > uint32_t head_idx, packet_success = 0;
> > uint16_t avail_idx, res_cur_idx;
> > uint16_t res_base_idx, res_end_idx;
> > @@ -113,6 +114,10 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t
> queue_id,
> > rte_prefetch0(&vq->desc[head[packet_success]]);
> >
> > while (res_cur_idx != res_end_idx) {
> > + uint32_t offset = 0, vb_offset = 0;
> > + uint32_t pkt_len, len_to_cpy, data_len, total_copied = 0;
> > + uint8_t hdr = 0, uncompleted_pkt = 0;
> > +
> > /* Get descriptor from available ring */
> > desc = &vq->desc[head[packet_success]];
> >
> > @@ -125,7 +130,6 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t
> > queue_id,
> >
> > /* Copy virtio_hdr to packet and increment buffer address */
> > buff_hdr_addr = buff_addr;
> > - packet_len = rte_pktmbuf_data_len(buff) + vq->vhost_hlen;
> >
> > /*
> > * If the descriptors are chained the header and data are @@
> > -136,28 +140,73 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t
> queue_id,
> > desc = &vq->desc[desc->next];
> > /* Buffer address translation. */
> > buff_addr = gpa_to_vva(dev, desc->addr);
> > - desc->len = rte_pktmbuf_data_len(buff);
> > } else {
> > - buff_addr += vq->vhost_hlen;
> > - desc->len = packet_len;
> > + vb_offset += vq->vhost_hlen;
> > + hdr = 1;
> > }
> >
> > + pkt_len = rte_pktmbuf_pkt_len(buff);
> > + data_len = rte_pktmbuf_data_len(buff);
> > + len_to_cpy = RTE_MIN(data_len,
> > + hdr ? desc->len - vq->vhost_hlen : desc->len);
> > + while (len_to_cpy > 0) {
> while (total_copied < pkt_len) is secure and readable.
> Besides, what if we encounter some descriptor with zero length? With
> len_to_cpy > 0, we would pass a partially copied mbuf to guest but still
> used->len = packet_len.
Good catch, will update it in v4.
> > + /* Copy mbuf data to buffer */
> > + rte_memcpy((void *)(uintptr_t)(buff_addr +
> vb_offset),
> > + (const void *)(rte_pktmbuf_mtod(buff,
> const char *) + offset),
> > + len_to_cpy);
> > + PRINT_PACKET(dev, (uintptr_t)(buff_addr +
> vb_offset),
> > + len_to_cpy, 0);
> > +
> > + offset += len_to_cpy;
> > + vb_offset += len_to_cpy;
> > + total_copied += len_to_cpy;
> > +
> > + /* The whole packet completes */
> > + if (total_copied == pkt_len)
> > + break;
> > +
> > + /* The current segment completes */
> > + if (offset == data_len) {
> > + buff = buff->next;
> > + if (buff != NULL) {
> > + offset = 0;
> > + data_len =
> rte_pktmbuf_data_len(buff);
> > + }
> What if (buf == NULL)? Either we treat mbuf reliable, and don't do any sanity
> check, or we check thoroughly.
> if (buff != NULL) {
The check could be removed, as another check " total_copied == pkt_len" can
guarantee when the current segment completes and
The whole packet doesn't complete, then the next must not be null.
Will update it in v4
>
> } else {
> ...
> break;
> }
> > + }
> > +
> > + /* The current vring descriptor done */
> > + if (vb_offset == desc->len) {
> > + if (desc->flags & VRING_DESC_F_NEXT) {
> > + desc = &vq->desc[desc->next];
> > + buff_addr = gpa_to_vva(dev, desc-
> >addr);
> > + vb_offset = 0;
> > + } else {
> > + /* Room in vring buffer is not enough
> */
> > + uncompleted_pkt = 1;
> > + break;
> > + }
> > + }
> > + len_to_cpy = RTE_MIN(data_len - offset, desc->len -
> vb_offset);
> > + };
> > +
> > /* Update used ring with desc information */
> > vq->used->ring[res_cur_idx & (vq->size - 1)].id =
> >
> head[packet_success];
> > - vq->used->ring[res_cur_idx & (vq->size - 1)].len =
> packet_len;
> >
> > - /* Copy mbuf data to buffer */
> > - /* FIXME for sg mbuf and the case that desc couldn't hold the
> mbuf data */
> > - rte_memcpy((void *)(uintptr_t)buff_addr,
> > - rte_pktmbuf_mtod(buff, const void *),
> > - rte_pktmbuf_data_len(buff));
> > - PRINT_PACKET(dev, (uintptr_t)buff_addr,
> > - rte_pktmbuf_data_len(buff), 0);
> > + /* Drop the packet if it is uncompleted */
> > + if (unlikely(uncompleted_pkt == 1))
> > + vq->used->ring[res_cur_idx & (vq->size - 1)].len =
> > + vq->vhost_hlen;
> > + else
> > + vq->used->ring[res_cur_idx & (vq->size - 1)].len =
> > + pkt_len + vq-
> >vhost_hlen;
> >
> > res_cur_idx++;
> > packet_success++;
> >
> > + if (unlikely(uncompleted_pkt == 1))
> > + continue;
> > +
> > rte_memcpy((void *)(uintptr_t)buff_hdr_addr,
> > (const void *)&virtio_hdr, vq->vhost_hlen);
> >
> > @@ -589,7 +638,14 @@ rte_vhost_dequeue_burst(struct virtio_net *dev,
> uint16_t queue_id,
> > desc = &vq->desc[head[entry_success]];
> >
> > /* Discard first buffer as it is the virtio header */
> > - desc = &vq->desc[desc->next];
> > + if (desc->flags & VRING_DESC_F_NEXT) {
> > + desc = &vq->desc[desc->next];
> > + vb_offset = 0;
> > + vb_avail = desc->len;
> > + } else {
> > + vb_offset = vq->vhost_hlen;
> > + vb_avail = desc->len - vb_offset;
> > + }
> >
> > /* Buffer address translation. */
> > vb_addr = gpa_to_vva(dev, desc->addr); @@ -608,8 +664,6
> @@
> > rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
> > vq->used->ring[used_idx].id = head[entry_success];
> > vq->used->ring[used_idx].len = 0;
> >
> > - vb_offset = 0;
> > - vb_avail = desc->len;
> > /* Allocate an mbuf and populate the structure. */
> > m = rte_pktmbuf_alloc(mbuf_pool);
> > if (unlikely(m == NULL)) {
