On 22.01.2019 20:01, Tiwei Bie wrote:
> This patch mainly fixed below issues in the packed ring based
> control vq support in virtio driver:
>
> 1. When parsing the used descriptors, we have to track the
> number of descs that we need to skip;
> 2. vq->vq_free_cnt was decreased twice for a same desc;
>
> Meanwhile, make the function name consistent with other parts.
>
> Fixes: ec194c2f1895 ("net/virtio: support packed queue in send command")
> Fixes: a4270ea4ff79 ("net/virtio: check head desc with correct wrap counter")
>
> Signed-off-by: Tiwei Bie <tiwei....@intel.com>
> ---
> drivers/net/virtio/virtio_ethdev.c | 62 ++++++++++++++----------------
> drivers/net/virtio/virtqueue.h | 12 +-----
> 2 files changed, 31 insertions(+), 43 deletions(-)
>
> diff --git a/drivers/net/virtio/virtio_ethdev.c
> b/drivers/net/virtio/virtio_ethdev.c
> index ee5a98b7c..a3fe65599 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -142,16 +142,17 @@ static const struct rte_virtio_xstats_name_off
> rte_virtio_txq_stat_strings[] = {
> struct virtio_hw_internal virtio_hw_internal[RTE_MAX_ETHPORTS];
>
> static struct virtio_pmd_ctrl *
> -virtio_pq_send_command(struct virtnet_ctl *cvq, struct virtio_pmd_ctrl *ctrl,
> - int *dlen, int pkt_num)
> +virtio_send_command_packed(struct virtnet_ctl *cvq,
> + struct virtio_pmd_ctrl *ctrl,
> + int *dlen, int pkt_num)
> {
> struct virtqueue *vq = cvq->vq;
> int head;
> struct vring_packed_desc *desc = vq->ring_packed.desc_packed;
> struct virtio_pmd_ctrl *result;
> - bool avail_wrap_counter, used_wrap_counter;
> - uint16_t flags;
> + bool avail_wrap_counter;
> int sum = 0;
> + int nb_descs = 0;
> int k;
>
> /*
> @@ -162,11 +163,10 @@ virtio_pq_send_command(struct virtnet_ctl *cvq, struct
> virtio_pmd_ctrl *ctrl,
> */
> head = vq->vq_avail_idx;
> avail_wrap_counter = vq->avail_wrap_counter;
> - used_wrap_counter = vq->used_wrap_counter;
> - desc[head].flags = VRING_DESC_F_NEXT;
> desc[head].addr = cvq->virtio_net_hdr_mem;
> desc[head].len = sizeof(struct virtio_net_ctrl_hdr);
> vq->vq_free_cnt--;
> + nb_descs++;
> if (++vq->vq_avail_idx >= vq->vq_nentries) {
> vq->vq_avail_idx -= vq->vq_nentries;
> vq->avail_wrap_counter ^= 1;
> @@ -177,55 +177,51 @@ virtio_pq_send_command(struct virtnet_ctl *cvq, struct
> virtio_pmd_ctrl *ctrl,
> + sizeof(struct virtio_net_ctrl_hdr)
> + sizeof(ctrl->status) + sizeof(uint8_t) * sum;
> desc[vq->vq_avail_idx].len = dlen[k];
> - flags = VRING_DESC_F_NEXT;
Looks like barriers was badly placed here before this patch.
Anyway, you need a write barrier here between {addr, len} and flags updates.
> + desc[vq->vq_avail_idx].flags = VRING_DESC_F_NEXT |
> + VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
> + VRING_DESC_F_USED(!vq->avail_wrap_counter);
> sum += dlen[k];
> vq->vq_free_cnt--;
> - flags |= VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
> - VRING_DESC_F_USED(!vq->avail_wrap_counter);
> - desc[vq->vq_avail_idx].flags = flags;
> - rte_smp_wmb();
> - vq->vq_free_cnt--;
> + nb_descs++;
> if (++vq->vq_avail_idx >= vq->vq_nentries) {
> vq->vq_avail_idx -= vq->vq_nentries;
> vq->avail_wrap_counter ^= 1;
> }
> }
>
> -
> desc[vq->vq_avail_idx].addr = cvq->virtio_net_hdr_mem
> + sizeof(struct virtio_net_ctrl_hdr);
> desc[vq->vq_avail_idx].len = sizeof(ctrl->status);
> - flags = VRING_DESC_F_WRITE;
> - flags |= VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
> - VRING_DESC_F_USED(!vq->avail_wrap_counter);
> - desc[vq->vq_avail_idx].flags = flags;
> - flags = VRING_DESC_F_NEXT;
> - flags |= VRING_DESC_F_AVAIL(avail_wrap_counter) |
> - VRING_DESC_F_USED(!avail_wrap_counter);
> - desc[head].flags = flags;
> - rte_smp_wmb();
> -
Same here. We need a write barrier to be sure that {addr, len} written
before updating flags.
Another way to avoid most of barriers is to work similar to
'flush_shadow_used_ring_packed',
i.e. update all the data in a loop - write barrier - update all the flags.
> + desc[vq->vq_avail_idx].flags = VRING_DESC_F_WRITE |
> + VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
> + VRING_DESC_F_USED(!vq->avail_wrap_counter);
> vq->vq_free_cnt--;
> + nb_descs++;
> if (++vq->vq_avail_idx >= vq->vq_nentries) {
> vq->vq_avail_idx -= vq->vq_nentries;
> vq->avail_wrap_counter ^= 1;
> }
>
> + virtio_wmb(vq->hw->weak_barriers);
> + desc[head].flags = VRING_DESC_F_NEXT |
> + VRING_DESC_F_AVAIL(avail_wrap_counter) |
> + VRING_DESC_F_USED(!avail_wrap_counter);
> +
> + virtio_wmb(vq->hw->weak_barriers);
> virtqueue_notify(vq);
>
> /* wait for used descriptors in virtqueue */
> - do {
> - rte_rmb();
> + while (!desc_is_used(&desc[head], vq))
> usleep(100);
> - } while (!__desc_is_used(&desc[head], used_wrap_counter));
> +
> + virtio_rmb(vq->hw->weak_barriers);
>
> /* now get used descriptors */
> - while (desc_is_used(&desc[vq->vq_used_cons_idx], vq)) {
> - vq->vq_free_cnt++;
> - if (++vq->vq_used_cons_idx >= vq->vq_nentries) {
> - vq->vq_used_cons_idx -= vq->vq_nentries;
> - vq->used_wrap_counter ^= 1;
> - }
> + vq->vq_free_cnt += nb_descs;
> + vq->vq_used_cons_idx += nb_descs;
> + if (vq->vq_used_cons_idx >= vq->vq_nentries) {
> + vq->vq_used_cons_idx -= vq->vq_nentries;
> + vq->used_wrap_counter ^= 1;
> }
>
> result = cvq->virtio_net_hdr_mz->addr;
> @@ -266,7 +262,7 @@ virtio_send_command(struct virtnet_ctl *cvq, struct
> virtio_pmd_ctrl *ctrl,
> sizeof(struct virtio_pmd_ctrl));
>
> if (vtpci_packed_queue(vq->hw)) {
> - result = virtio_pq_send_command(cvq, ctrl, dlen, pkt_num);
> + result = virtio_send_command_packed(cvq, ctrl, dlen, pkt_num);
> goto out_unlock;
> }
>
> diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
> index 7fcde5643..ca9d8e6e3 100644
> --- a/drivers/net/virtio/virtqueue.h
> +++ b/drivers/net/virtio/virtqueue.h
> @@ -281,7 +281,7 @@ struct virtio_tx_region {
> };
>
> static inline int
> -__desc_is_used(struct vring_packed_desc *desc, bool wrap_counter)
> +desc_is_used(struct vring_packed_desc *desc, struct virtqueue *vq)
> {
> uint16_t used, avail, flags;
>
> @@ -289,16 +289,9 @@ __desc_is_used(struct vring_packed_desc *desc, bool
> wrap_counter)
> used = !!(flags & VRING_DESC_F_USED(1));
> avail = !!(flags & VRING_DESC_F_AVAIL(1));
>
> - return avail == used && used == wrap_counter;
> + return avail == used && used == vq->used_wrap_counter;
> }
>
> -static inline int
> -desc_is_used(struct vring_packed_desc *desc, struct virtqueue *vq)
> -{
> - return __desc_is_used(desc, vq->used_wrap_counter);
> -}
> -
> -
> static inline void
> vring_desc_init_packed(struct virtqueue *vq, int n)
> {
> @@ -354,7 +347,6 @@ virtqueue_enable_intr_packed(struct virtqueue *vq)
> {
> uint16_t *event_flags = &vq->ring_packed.driver_event->desc_event_flags;
>
> -
> if (vq->event_flags_shadow == RING_EVENT_FLAGS_DISABLE) {
> virtio_wmb(vq->hw->weak_barriers);
> vq->event_flags_shadow = RING_EVENT_FLAGS_ENABLE;
>
