Re: [dpdk-dev] [PATCH v10 7/9] net/virtio: add virtio send command packed queue support

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 11/2/18 10:07 AM, Jens Freimann wrote:
> Use packed virtqueue format when reading and writing descriptors
> to/from the ring.
> 
> Signed-off-by: Jens Freimann <jfreimann@redhat.com>
> ---
>   drivers/net/virtio/virtio_ethdev.c | 90 ++++++++++++++++++++++++++++++
>   1 file changed, 90 insertions(+)
> 
> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
> index ed3d5bd2c..4451dd49b 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -141,6 +141,90 @@ 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)
> +{
> +	struct virtqueue *vq = cvq->vq;
> +	int head;
> +	struct vring_desc_packed *desc = vq->ring_packed.desc_packed;
> +	struct virtio_pmd_ctrl *result;
> +	int wrap_counter;
> +	int sum = 0;
> +	int k;
> +
> +	/*
> +	 * Format is enforced in qemu code:
> +	 * One TX packet for header;
> +	 * At least one TX packet per argument;
> +	 * One RX packet for ACK.
> +	 */
> +	head = vq->vq_avail_idx;
> +	wrap_counter = vq->avail_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--;
> +	if (++vq->vq_avail_idx >= vq->vq_nentries) {
> +		vq->vq_avail_idx -= vq->vq_nentries;
> +		vq->avail_wrap_counter ^= 1;
> +	}
> +
> +	for (k = 0; k < pkt_num; k++) {
> +		desc[vq->vq_avail_idx].addr = cvq->virtio_net_hdr_mem
> +			+ sizeof(struct virtio_net_ctrl_hdr)
> +			+ sizeof(ctrl->status) + sizeof(uint8_t) * sum;
> +		desc[vq->vq_avail_idx].len = dlen[k];
> +		desc[vq->vq_avail_idx].flags = VRING_DESC_F_NEXT;
> +		sum += dlen[k];
> +		vq->vq_free_cnt--;
> +		_set_desc_avail(&desc[vq->vq_avail_idx],
> +				vq->avail_wrap_counter);
> +		rte_smp_wmb();
> +		vq->vq_free_cnt--;
> +		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);
> +	desc[vq->vq_avail_idx].flags = VRING_DESC_F_WRITE;
> +	_set_desc_avail(&desc[vq->vq_avail_idx],
> +			vq->avail_wrap_counter);
> +	_set_desc_avail(&desc[head], wrap_counter);
> +	rte_smp_wmb();
> +
> +	vq->vq_free_cnt--;
> +	if (++vq->vq_avail_idx >= vq->vq_nentries) {
> +		vq->vq_avail_idx -= vq->vq_nentries;
> +		vq->avail_wrap_counter ^= 1;
> +	}
> +
> +	virtqueue_notify(vq);
> +
> +	/* wait for used descriptors in virtqueue */
> +	do {
> +		rte_rmb();
> +		usleep(100);
> +	} while (!desc_is_used(&desc[head], vq));

Maybe better to poll for !desc_is_used(&desc[vq->vq_used_cons_idx], vq))
to make it clear we're safe using used_wrap_counter?

> +
> +	/* 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;
> +		}
> +	}
> +
> +	result = cvq->virtio_net_hdr_mz->addr;
> +	return result;
> +}
> +
>   static int
>   virtio_send_command(struct virtnet_ctl *cvq, struct virtio_pmd_ctrl *ctrl,
>   		int *dlen, int pkt_num)
> @@ -174,6 +258,11 @@ virtio_send_command(struct virtnet_ctl *cvq, struct virtio_pmd_ctrl *ctrl,
>   	memcpy(cvq->virtio_net_hdr_mz->addr, ctrl,
>   		sizeof(struct virtio_pmd_ctrl));
>   
> +	if (vtpci_packed_queue(vq->hw)) {
> +		result = virtio_pq_send_command(cvq, ctrl, dlen, pkt_num);
> +		goto out_unlock;
> +	}
> +
>   	/*
>   	 * Format is enforced in qemu code:
>   	 * One TX packet for header;
> @@ -245,6 +334,7 @@ virtio_send_command(struct virtnet_ctl *cvq, struct virtio_pmd_ctrl *ctrl,
>   
>   	result = cvq->virtio_net_hdr_mz->addr;
>   
> +out_unlock:
>   	rte_spinlock_unlock(&cvq->lock);
>   	return result->status;
>   }
>