Re: [dpdk-dev] [PATCH v5 2/4] vhost: add support for packed ring in async vhost

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

On 4/13/21 1:48 PM, Jiang, Cheng1 wrote:
> Hi Maxime,
> 
>> -----Original Message-----
>> From: Maxime Coquelin <maxime.coquelin@redhat.com>
>> Sent: Tuesday, April 13, 2021 4:37 PM
>> To: Jiang, Cheng1 <cheng1.jiang@intel.com>; Xia, Chenbo
>> <chenbo.xia@intel.com>
>> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Yang, YvonneX
>> <yvonnex.yang@intel.com>; Wang, Yinan <yinan.wang@intel.com>; Liu,
>> Yong <yong.liu@intel.com>
>> Subject: Re: [PATCH v5 2/4] vhost: add support for packed ring in async vhost
>>
>>
>>
>> On 4/12/21 1:34 PM, Cheng Jiang wrote:
>>> For now async vhost data path only supports split ring structure. In
>>> order to make async vhost compatible with virtio 1.1 spec this patch
>>> enables packed ring in async vhost data path.
>>>
>>> Signed-off-by: Cheng Jiang <Cheng1.jiang@intel.com>
>>> ---
>>>  lib/librte_vhost/rte_vhost_async.h |   1 +
>>>  lib/librte_vhost/vhost.c           |  27 +-
>>>  lib/librte_vhost/vhost.h           |   7 +-
>>>  lib/librte_vhost/virtio_net.c      | 438 +++++++++++++++++++++++++++--
>>>  4 files changed, 448 insertions(+), 25 deletions(-)
>>>
>>> diff --git a/lib/librte_vhost/rte_vhost_async.h
>>> b/lib/librte_vhost/rte_vhost_async.h
>>> index c855ff875..6faa31f5a 100644
>>> --- a/lib/librte_vhost/rte_vhost_async.h
>>> +++ b/lib/librte_vhost/rte_vhost_async.h
>>> @@ -89,6 +89,7 @@ struct rte_vhost_async_channel_ops {  struct
>>> async_inflight_info {
>>>  	struct rte_mbuf *mbuf;
>>>  	uint16_t descs; /* num of descs inflight */
>>> +	uint16_t nr_buffers; /* num of buffers inflight for packed ring */
>>>  };
>>>
>>>  /**
>>> diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c index
>>> a70fe01d8..8c9935c0f 100644
>>> --- a/lib/librte_vhost/vhost.c
>>> +++ b/lib/librte_vhost/vhost.c
>>> @@ -342,15 +342,21 @@ vhost_free_async_mem(struct vhost_virtqueue
>> *vq)
>>> {
>>>  	if (vq->async_pkts_info)
>>>  		rte_free(vq->async_pkts_info);
>>> -	if (vq->async_descs_split)
>>> +	if (vq->async_buffers_packed) {
>>> +		rte_free(vq->async_buffers_packed);
>>> +		vq->async_buffers_packed = NULL;
>>> +	}
>>> +	if (vq->async_descs_split) {
>>
>> You can remove the check, rte_free is safe with NULL pointers.
>> You can do the same for the other ones in this function.
> 
> OK, it will be fixed.
> 
>>
>>>  		rte_free(vq->async_descs_split);
>>> +		vq->async_descs_split = NULL;
>>> +	}
>>> +
>>>  	if (vq->it_pool)
>>>  		rte_free(vq->it_pool);
>>>  	if (vq->vec_pool)
>>>  		rte_free(vq->vec_pool);
>>>
>>>  	vq->async_pkts_info = NULL;
>>> -	vq->async_descs_split = NULL;
>>>  	vq->it_pool = NULL;
>>>  	vq->vec_pool = NULL;
>>>  }
>>> @@ -1627,9 +1633,9 @@ int rte_vhost_async_channel_register(int vid,
>> uint16_t queue_id,
>>>  		return -1;
>>>
>>>  	/* packed queue is not supported */
>>> -	if (unlikely(vq_is_packed(dev) || !f.async_inorder)) {
>>> +	if (unlikely(!f.async_inorder)) {
>>>  		VHOST_LOG_CONFIG(ERR,
>>> -			"async copy is not supported on packed queue or
>> non-inorder mode "
>>> +			"async copy is not supported on non-inorder mode "
>>>  			"(vid %d, qid: %d)\n", vid, queue_id);
>>>  		return -1;
>>>  	}
>>> @@ -1667,11 +1673,18 @@ int rte_vhost_async_channel_register(int vid,
>> uint16_t queue_id,
>>>  	vq->vec_pool = rte_malloc_socket(NULL,
>>>  			VHOST_MAX_ASYNC_VEC * sizeof(struct iovec),
>>>  			RTE_CACHE_LINE_SIZE, node);
>>> -	vq->async_descs_split = rte_malloc_socket(NULL,
>>> +	if (vq_is_packed(dev)) {
>>> +		vq->async_buffers_packed = rte_malloc_socket(NULL,
>>> +			vq->size * sizeof(struct vring_used_elem_packed),
>>> +			RTE_CACHE_LINE_SIZE, node);
>>> +	} else {
>>> +		vq->async_descs_split = rte_malloc_socket(NULL,
>>>  			vq->size * sizeof(struct vring_used_elem),
>>>  			RTE_CACHE_LINE_SIZE, node);
>>> -	if (!vq->async_descs_split || !vq->async_pkts_info ||
>>> -		!vq->it_pool || !vq->vec_pool) {
>>> +	}
>>> +
>>> +	if (!vq->async_buffers_packed || !vq->async_descs_split ||
>>> +		!vq->async_pkts_info || !vq->it_pool || !vq->vec_pool) {
>>>  		vhost_free_async_mem(vq);
>>>  		VHOST_LOG_CONFIG(ERR,
>>>  				"async register failed: cannot allocate
>> memory for vq data "
>>> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h index
>>> f628714c2..fe131ae8f 100644
>>> --- a/lib/librte_vhost/vhost.h
>>> +++ b/lib/librte_vhost/vhost.h
>>> @@ -201,9 +201,14 @@ struct vhost_virtqueue {
>>>  	uint16_t	async_pkts_idx;
>>>  	uint16_t	async_pkts_inflight_n;
>>>  	uint16_t	async_last_pkts_n;
>>> -	struct vring_used_elem  *async_descs_split;
>>> +	union {
>>> +		struct vring_used_elem  *async_descs_split;
>>> +		struct vring_used_elem_packed *async_buffers_packed;
>>> +	};
>>>  	uint16_t async_desc_idx;
>>> +	uint16_t async_packed_buffer_idx;
>>
>> Don't dupplicate variable names, async_desc_idx can be reused for packed
>> ring. Also, they are representing the same thing, why use desc in one case
>> and buffer in the other?
> 
> The main reason is that the unit of the packed used ring is buffer, which can contain many desc.
> I think using desc_idx will cause ambiguity, but if you think that I should reuse the desc_idx, I have no problem with that.

OK, in this case please use a union not to waste memory.

>>
>>>  	uint16_t last_async_desc_idx;
>>> +	uint16_t last_async_buffer_idx;
>>
>> Same remark here.
>>
>>>  	/* vq async features */
>>>  	bool		async_inorder;
>>> diff --git a/lib/librte_vhost/virtio_net.c
>>> b/lib/librte_vhost/virtio_net.c index c43ab0093..410be9678 100644
>>> --- a/lib/librte_vhost/virtio_net.c
>>> +++ b/lib/librte_vhost/virtio_net.c
>>> @@ -363,14 +363,14 @@
>>> vhost_shadow_dequeue_single_packed_inorder(struct vhost_virtqueue
>> *vq,
>>> }
>>>
>>>  static __rte_always_inline void
>>> -vhost_shadow_enqueue_single_packed(struct virtio_net *dev,
>>> -				   struct vhost_virtqueue *vq,
>>> -				   uint32_t len[],
>>> -				   uint16_t id[],
>>> -				   uint16_t count[],
>>> +vhost_shadow_enqueue_packed(struct vhost_virtqueue *vq,
>>> +				   uint32_t *len,
>>> +				   uint16_t *id,
>>> +				   uint16_t *count,
>>>  				   uint16_t num_buffers)
>>>  {
>>>  	uint16_t i;
>>> +
>>>  	for (i = 0; i < num_buffers; i++) {
>>>  		/* enqueue shadow flush action aligned with batch num */
>>>  		if (!vq->shadow_used_idx)
>>> @@ -382,6 +382,17 @@ vhost_shadow_enqueue_single_packed(struct
>> virtio_net *dev,
>>>  		vq->shadow_aligned_idx += count[i];
>>>  		vq->shadow_used_idx++;
>>>  	}
>>> +}
>>> +
>>> +static __rte_always_inline void
>>> +vhost_shadow_enqueue_single_packed(struct virtio_net *dev,
>>> +				   struct vhost_virtqueue *vq,
>>> +				   uint32_t *len,
>>> +				   uint16_t *id,
>>> +				   uint16_t *count,
>>> +				   uint16_t num_buffers)
>>> +{
>>> +	vhost_shadow_enqueue_packed(vq, len, id, count, num_buffers);
>>>
>>>  	if (vq->shadow_aligned_idx >= PACKED_BATCH_SIZE) {
>>>  		do_data_copy_enqueue(dev, vq);
>>> @@ -1481,6 +1492,62 @@ shadow_ring_store(struct vhost_virtqueue *vq,
>> void *shadow_ring, void *d_ring,
>>>  	}
>>>  }
>>>
>>> +static __rte_always_inline void
>>> +vhost_update_used_packed(struct vhost_virtqueue *vq,
>>> +			struct vring_used_elem_packed *shadow_ring,
>>> +			uint16_t count)
>>> +{
>>> +	if (count == 0)
>>> +		return;
>>
>> Move this after the variables declaration.
> 
> Sure.
> 
>>
>>> +
>>> +	int i;
>>> +	uint16_t used_idx = vq->last_used_idx;
>>> +	uint16_t head_idx = vq->last_used_idx;
>>> +	uint16_t head_flags = 0;
>>> +
>>> +	/* Split loop in two to save memory barriers */
>>> +	for (i = 0; i < count; i++) {
>>> +		vq->desc_packed[used_idx].id = shadow_ring[i].id;
>>> +		vq->desc_packed[used_idx].len = shadow_ring[i].len;
>>> +
>>> +		used_idx += shadow_ring[i].count;
>>> +		if (used_idx >= vq->size)
>>> +			used_idx -= vq->size;
>>> +	}
>>> +
>>> +	/* The ordering for storing desc flags needs to be enforced. */
>>> +	rte_atomic_thread_fence(__ATOMIC_RELEASE);
>>> +
>>> +	for (i = 0; i < count; i++) {
>>> +		uint16_t flags;
>>> +
>>> +		if (vq->shadow_used_packed[i].len)
>>> +			flags = VRING_DESC_F_WRITE;
>>> +		else
>>> +			flags = 0;
>>> +
>>> +		if (vq->used_wrap_counter) {
>>> +			flags |= VRING_DESC_F_USED;
>>> +			flags |= VRING_DESC_F_AVAIL;
>>> +		} else {
>>> +			flags &= ~VRING_DESC_F_USED;
>>> +			flags &= ~VRING_DESC_F_AVAIL;
>>> +		}
>>> +
>>> +		if (i > 0) {
>>> +			vq->desc_packed[vq->last_used_idx].flags = flags;
>>> +
>>> +		} else {
>>> +			head_idx = vq->last_used_idx;
>>> +			head_flags = flags;
>>> +		}
>>> +
>>> +		vq_inc_last_used_packed(vq, shadow_ring[i].count);
>>> +	}
>>> +
>>> +	vq->desc_packed[head_idx].flags = head_flags; }
>>> +
>>>  static __rte_noinline uint32_t
>>>  virtio_dev_rx_async_submit_split(struct virtio_net *dev,
>>>  	struct vhost_virtqueue *vq, uint16_t queue_id, @@ -1656,6
>> +1723,294
>>> @@ virtio_dev_rx_async_submit_split(struct virtio_net *dev,
>>>  	return pkt_idx;
>>>  }
>>>
>>> +static __rte_always_inline int
>>> +vhost_enqueue_async_single_packed(struct virtio_net *dev,
>>> +			    struct vhost_virtqueue *vq,
>>> +			    struct rte_mbuf *pkt,
>>> +			    struct buf_vector *buf_vec,
>>> +			    uint16_t *nr_descs,
>>> +			    uint16_t *nr_buffers,
>>> +			    struct vring_packed_desc *async_descs,
>>> +			    struct iovec *src_iovec, struct iovec *dst_iovec,
>>> +			    struct rte_vhost_iov_iter *src_it,
>>> +			    struct rte_vhost_iov_iter *dst_it) {
>>> +	uint16_t nr_vec = 0;
>>> +	uint16_t avail_idx = vq->last_avail_idx;
>>> +	uint16_t max_tries, tries = 0;
>>> +	uint16_t buf_id = 0;
>>> +	uint32_t len = 0;
>>> +	uint16_t desc_count = 0;
>>> +	uint32_t size = pkt->pkt_len + sizeof(struct
>> virtio_net_hdr_mrg_rxbuf);
>>> +	uint32_t buffer_len[vq->size];
>>> +	uint16_t buffer_buf_id[vq->size];
>>> +	uint16_t buffer_desc_count[vq->size];
>>> +	*nr_buffers = 0;
>>> +
>>> +	if (rxvq_is_mergeable(dev))
>>> +		max_tries = vq->size - 1;
>>> +	else
>>> +		max_tries = 1;
>>> +
>>> +	while (size > 0) {
>>> +		/*
>>> +		 * if we tried all available ring items, and still
>>> +		 * can't get enough buf, it means something abnormal
>>> +		 * happened.
>>> +		 */
>>> +		if (unlikely(++tries > max_tries))
>>> +			return -1;
>>> +
>>> +		if (unlikely(fill_vec_buf_packed(dev, vq,
>>> +						avail_idx, &desc_count,
>>> +						buf_vec, &nr_vec,
>>> +						&buf_id, &len,
>>> +						VHOST_ACCESS_RW) < 0))
>>> +			return -1;
>>> +
>>> +		len = RTE_MIN(len, size);
>>> +		size -= len;
>>> +
>>> +		buffer_len[*nr_buffers] = len;
>>> +		buffer_buf_id[*nr_buffers] = buf_id;
>>> +		buffer_desc_count[*nr_buffers] = desc_count;
>>> +		*nr_buffers += 1;
>>> +
>>> +		*nr_descs += desc_count;
>>> +		avail_idx += desc_count;
>>> +		if (avail_idx >= vq->size)
>>> +			avail_idx -= vq->size;
>>> +	}
>>> +
>>> +	if (async_mbuf_to_desc(dev, vq, pkt, buf_vec, nr_vec, *nr_buffers,
>>> +		src_iovec, dst_iovec, src_it, dst_it) < 0)
>>> +		return -1;
>>> +	/* store descriptors for DMA */
>>> +	if (avail_idx >= *nr_descs)
>>> +		rte_memcpy(async_descs,
>>> +			&vq->desc_packed[vq->last_avail_idx],
>>> +			*nr_descs * sizeof(struct vring_packed_desc));
>>
>> Please add brackets for the 'if' since there are for the 'else'.
> 
> Sure, sorry for that.
> 
>>
>>> +	else {
>>> +		uint16_t nr_copy = vq->size - vq->last_avail_idx;
>>> +		rte_memcpy(async_descs,
>>> +			&vq->desc_packed[vq->last_avail_idx],
>>> +			nr_copy * sizeof(struct vring_packed_desc));
>>> +		rte_memcpy(async_descs + nr_copy,
>>> +			vq->desc_packed, (*nr_descs - nr_copy) *
>>> +			sizeof(struct vring_packed_desc));
>>> +	}
>>> +
>>> +	vhost_shadow_enqueue_packed(vq, buffer_len, buffer_buf_id,
>>> +					   buffer_desc_count, *nr_buffers);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static __rte_always_inline int16_t
>>> +virtio_dev_rx_async_single_packed(struct virtio_net *dev,
>>> +			    struct vhost_virtqueue *vq,
>>> +			    struct rte_mbuf *pkt,
>>> +			    uint16_t *nr_descs, uint16_t *nr_buffers,
>>> +			    struct vring_packed_desc *async_descs,
>>> +			    struct iovec *src_iovec, struct iovec *dst_iovec,
>>> +			    struct rte_vhost_iov_iter *src_it,
>>> +			    struct rte_vhost_iov_iter *dst_it) {
>>> +	struct buf_vector buf_vec[BUF_VECTOR_MAX];
>>> +	*nr_descs = 0;
>>> +	*nr_buffers = 0;
>>> +
>>> +	if (unlikely(vhost_enqueue_async_single_packed(dev, vq, pkt,
>> buf_vec,
>>> +						 nr_descs,
>>> +						 nr_buffers,
>>> +						 async_descs,
>>> +						 src_iovec, dst_iovec,
>>> +						 src_it, dst_it) < 0)) {
>>> +		VHOST_LOG_DATA(DEBUG,
>>> +				"(%d) failed to get enough desc from vring\n",
>>> +				dev->vid);
>>> +		return -1;
>>> +	}
>>> +
>>> +	VHOST_LOG_DATA(DEBUG, "(%d) current index %d | end
>> index %d\n",
>>> +			dev->vid, vq->last_avail_idx,
>>> +			vq->last_avail_idx + *nr_descs);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static __rte_noinline uint32_t
>>> +virtio_dev_rx_async_submit_packed(struct virtio_net *dev,
>>> +	struct vhost_virtqueue *vq, uint16_t queue_id,
>>> +	struct rte_mbuf **pkts, uint32_t count,
>>> +	struct rte_mbuf **comp_pkts, uint32_t *comp_count) {
>>> +	uint32_t pkt_idx = 0, pkt_burst_idx = 0;
>>> +	uint16_t async_descs_idx = 0;
>>> +	uint16_t num_buffers;
>>> +	uint16_t num_desc;
>>> +
>>> +	struct rte_vhost_iov_iter *it_pool = vq->it_pool;
>>> +	struct iovec *vec_pool = vq->vec_pool;
>>> +	struct rte_vhost_async_desc tdes[MAX_PKT_BURST];
>>> +	struct iovec *src_iovec = vec_pool;
>>> +	struct iovec *dst_iovec = vec_pool + (VHOST_MAX_ASYNC_VEC >>
>> 1);
>>> +	struct rte_vhost_iov_iter *src_it = it_pool;
>>> +	struct rte_vhost_iov_iter *dst_it = it_pool + 1;
>>> +	uint16_t slot_idx = 0;
>>> +	uint16_t segs_await = 0;
>>> +	uint16_t iovec_idx = 0, it_idx = 0;
>>> +	struct async_inflight_info *pkts_info = vq->async_pkts_info;
>>> +	uint32_t n_pkts = 0, pkt_err = 0;
>>> +	uint32_t num_async_pkts = 0, num_done_pkts = 0;
>>> +	struct vring_packed_desc async_descs[vq->size];
>>> +
>>> +	rte_prefetch0(&vq->desc_packed[vq->last_avail_idx & (vq->size -
>>> +1)]);
>>
>> The size of the ring is not necessarily a power of two with packed ring.
> 
> For the size of the ring is not necessarily a power of two,
> so maybe I can use codes like 
> Indx % vq->size  ?
> I'm not sure if it's a good way to do that.

In this case it is OK.

>>
>>> +
>>> +	for (pkt_idx = 0; pkt_idx < count; pkt_idx++) {
>>> +		if (unlikely(virtio_dev_rx_async_single_packed(dev, vq,
>>> +						pkts[pkt_idx],
>>> +						&num_desc, &num_buffers,
>>> +
>> 	&async_descs[async_descs_idx],
>>> +						&src_iovec[iovec_idx],
>>> +						&dst_iovec[iovec_idx],
>>> +						&src_it[it_idx],
>>> +						&dst_it[it_idx]) < 0))
>>> +			break;
>>> +
>>> +		VHOST_LOG_DATA(DEBUG, "(%d) current index %d | end
>> index %d\n",
>>> +			dev->vid, vq->last_avail_idx,
>>> +			vq->last_avail_idx + num_desc);
>>> +
>>> +		slot_idx = (vq->async_pkts_idx + num_async_pkts) &
>>> +			(vq->size - 1);
>>
>> Same here.
> 
> Sure.
> 
>>
>>> +		if (src_it[it_idx].count) {
>>> +			uint16_t from, to;
>>> +
>>> +			async_descs_idx += num_desc;
>>> +			async_fill_desc(&tdes[pkt_burst_idx++],
>> &src_it[it_idx],
>>> +					&dst_it[it_idx]);
>>> +			pkts_info[slot_idx].descs = num_desc;
>>> +			pkts_info[slot_idx].nr_buffers = num_buffers;
>>> +			pkts_info[slot_idx].mbuf = pkts[pkt_idx];
>>> +			num_async_pkts++;
>>> +			iovec_idx += src_it[it_idx].nr_segs;
>>> +			it_idx += 2;
>>> +
>>> +			segs_await += src_it[it_idx].nr_segs;
>>> +
>>> +			/**
>>> +			 * recover shadow used ring and keep DMA-occupied
>>> +			 * descriptors.
>>> +			 */
>>> +			from = vq->shadow_used_idx - num_buffers;
>>> +			to = vq->async_packed_buffer_idx & (vq->size - 1);
>>> +			shadow_ring_store(vq, vq->shadow_used_packed,
>>> +					vq->async_buffers_packed,
>>> +					from, to, num_buffers,
>>> +					sizeof(struct
>> vring_used_elem_packed));
>>> +
>>> +			vq->async_packed_buffer_idx += num_buffers;
>>> +			vq->shadow_used_idx -= num_buffers;
>>> +		} else
>>
>> Brackets needed.
> 
> Sure.
> 
>>
>>> +			comp_pkts[num_done_pkts++] = pkts[pkt_idx];
>>> +
>>> +		vq_inc_last_avail_packed(vq, num_desc);
>>> +
>>> +		/*
>>> +		 * conditions to trigger async device transfer:
>>> +		 * - buffered packet number reaches transfer threshold
>>> +		 * - unused async iov number is less than max vhost vector
>>> +		 */
>>> +		if (unlikely(pkt_burst_idx >=
>> VHOST_ASYNC_BATCH_THRESHOLD ||
>>> +			((VHOST_MAX_ASYNC_VEC >> 1) - segs_await <
>>> +			BUF_VECTOR_MAX))) {
>>> +			n_pkts = vq->async_ops.transfer_data(dev->vid,
>>> +					queue_id, tdes, 0, pkt_burst_idx);
>>> +			iovec_idx = 0;
>>> +			it_idx = 0;
>>> +			segs_await = 0;
>>> +			vq->async_pkts_inflight_n += n_pkts;
>>> +
>>> +			if (unlikely(n_pkts < pkt_burst_idx)) {
>>> +				/*
>>> +				 * log error packets number here and do
>> actual
>>> +				 * error processing when applications poll
>>> +				 * completion
>>> +				 */
>>> +				pkt_err = pkt_burst_idx - n_pkts;
>>> +				pkt_burst_idx = 0;
>>> +				pkt_idx++;
>>> +				break;
>>> +			}
>>> +
>>> +			pkt_burst_idx = 0;
>>> +		}
>>> +	}
>>> +
>>> +	if (pkt_burst_idx) {
>>> +		n_pkts = vq->async_ops.transfer_data(dev->vid,
>>> +				queue_id, tdes, 0, pkt_burst_idx);
>>> +		vq->async_pkts_inflight_n += n_pkts;
>>> +
>>> +		if (unlikely(n_pkts < pkt_burst_idx))
>>> +			pkt_err = pkt_burst_idx - n_pkts;
>>> +	}
>>> +
>>> +	do_data_copy_enqueue(dev, vq);
>>> +
>>> +	if (unlikely(pkt_err)) {
>>> +		uint16_t descs_err = 0;
>>> +		uint16_t buffers_err = 0;
>>> +
>>> +		num_async_pkts -= pkt_err;
>>> +		pkt_idx -= pkt_err;
>>> +	/* calculate the sum of buffers and descs of DMA-error packets. */
>>> +		while (pkt_err-- > 0) {
>>> +			descs_err +=
>>> +				pkts_info[slot_idx & (vq->size - 1)].descs;
>>
>> The size of the ring is not necessarily a power of two with packed ring.
> 
> Will be fixed.
> 
>>
>>> +			buffers_err +=
>>> +				pkts_info[slot_idx & (vq->size -
>> 1)].nr_buffers;
>>
>> Ditto.
> 
> Will be fixed.
> 
>>
>>> +			slot_idx--;
>>> +		}
>>> +
>>> +		vq->async_packed_buffer_idx -= buffers_err;
>>> +
>>> +		if (vq->last_avail_idx >= descs_err) {
>>> +			vq->last_avail_idx -= descs_err;
>>> +
>>> +			rte_memcpy(&vq->desc_packed[vq->last_avail_idx],
>>> +				&async_descs[async_descs_idx - descs_err],
>>> +				descs_err * sizeof(struct
>> vring_packed_desc));
>>> +		} else {
>>> +			uint16_t nr_copy;
>>> +
>>> +			vq->last_avail_idx = vq->last_avail_idx + vq->size
>>> +						- descs_err;
>>> +			nr_copy = vq->size - vq->last_avail_idx;
>>> +			rte_memcpy(&vq->desc_packed[vq->last_avail_idx],
>>> +				&async_descs[async_descs_idx - descs_err],
>>> +				nr_copy * sizeof(struct vring_packed_desc));
>>> +			descs_err -= nr_copy;
>>> +			rte_memcpy(vq->desc_packed,
>>> +				&async_descs[async_descs_idx - descs_err],
>>> +				descs_err * sizeof(struct
>> vring_packed_desc));
>>> +			vq->avail_wrap_counter ^= 1;
>>> +		}
>>> +
>>> +		num_done_pkts = pkt_idx - num_async_pkts;
>>> +	}
>>
>> This error handling could be moved in a dedicated function.
> 
> Sure, will fix it in the next version.
> 
>>
>>> +	vq->async_pkts_idx += num_async_pkts;
>>> +	*comp_count = num_done_pkts;
>>> +
>>> +	if (likely(vq->shadow_used_idx)) {
>>> +		vhost_flush_enqueue_shadow_packed(dev, vq);
>>> +		vhost_vring_call_packed(dev, vq);
>>> +	}
>>> +
>>> +	return pkt_idx;
>>> +}
>>
>> Above function is very big and complex, it should be possible to split it in
>> several ones to make it maintainable.
> 
> I think move the error handling code will make it smaller.
> 
> Thanks.
> Cheng
> 
>>
>>> +
>>>  static __rte_always_inline void
>>>  write_back_completed_descs_split(struct vhost_virtqueue *vq, uint16_t
>>> n_descs)  { @@ -1693,12 +2048,40 @@
>>> write_back_completed_descs_split(struct vhost_virtqueue *vq, uint16_t
>> n_descs)
>>>  	} while (nr_left > 0);
>>>  }
>>>
>>> +static __rte_always_inline void
>>> +write_back_completed_descs_packed(struct vhost_virtqueue *vq,
>>> +				uint16_t n_buffers)
>>> +{
>>> +	uint16_t nr_left = n_buffers;
>>> +	uint16_t from, to;
>>> +
>>> +	do {
>>> +		from = vq->last_async_buffer_idx &
>>> +						(vq->size - 1);
>>> +		to = (from + nr_left) & (vq->size - 1);
>>
>> The size of the ring is not necessarily a power of two with packed ring.
> 
> Sure.
> 
>>
>>> +		if (to > from) {
>>> +			vhost_update_used_packed(vq,
>>> +				vq->async_buffers_packed + from,
>>> +				to - from);
>>> +			vq->last_async_buffer_idx += nr_left;
>>> +			nr_left = 0;
>>> +		} else {
>>> +			vhost_update_used_packed(vq,
>>> +				vq->async_buffers_packed + from,
>>> +				vq->size - from);
>>> +			vq->last_async_buffer_idx +=
>>> +						vq->size - from;
>>> +			nr_left -= vq->size - from;
>>> +		}
>>> +	} while (nr_left > 0);
>>> +}
>>> +
>>>  uint16_t rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
>>>  		struct rte_mbuf **pkts, uint16_t count)  {
>>>  	struct virtio_net *dev = get_device(vid);
>>>  	struct vhost_virtqueue *vq;
>>> -	uint16_t n_pkts_cpl = 0, n_pkts_put = 0, n_descs = 0;
>>> +	uint16_t n_pkts_cpl = 0, n_pkts_put = 0, n_descs = 0, n_buffers = 0;
>>>  	uint16_t start_idx, pkts_idx, vq_size;
>>>  	struct async_inflight_info *pkts_info;
>>>  	uint16_t from, i;
>>> @@ -1740,21 +2123,41 @@ uint16_t
>> rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
>>>  		goto done;
>>>  	}
>>>
>>> -	for (i = 0; i < n_pkts_put; i++) {
>>> -		from = (start_idx + i) & (vq_size - 1);
>>> -		n_descs += pkts_info[from].descs;
>>> -		pkts[i] = pkts_info[from].mbuf;
>>> +	if (vq_is_packed(dev)) {
>>> +		for (i = 0; i < n_pkts_put; i++) {
>>> +			from = (start_idx + i) & (vq_size - 1);
>>
>> Unlike split ring, packed ring size is not necessarily a power of 2.
> 
> Sure.
> Thanks.
> 
>>
>>> +			n_buffers += pkts_info[from].nr_buffers;
>>> +			pkts[i] = pkts_info[from].mbuf;
>>> +		}
>>> +	} else {
>>> +		for (i = 0; i < n_pkts_put; i++) {
>>> +			from = (start_idx + i) & (vq_size - 1);
>>> +			n_descs += pkts_info[from].descs;
>>> +			pkts[i] = pkts_info[from].mbuf;
>>> +		}
>>>  	}
>>> +
>>>  	vq->async_last_pkts_n = n_pkts_cpl - n_pkts_put;
>>>  	vq->async_pkts_inflight_n -= n_pkts_put;
>>>
>>>  	if (likely(vq->enabled && vq->access_ok)) {
>>> -		write_back_completed_descs_split(vq, n_descs);
>>> +		if (vq_is_packed(dev)) {
>>> +			write_back_completed_descs_packed(vq,
>> n_buffers);
>>>
>>> -		__atomic_add_fetch(&vq->used->idx, n_descs,
>> __ATOMIC_RELEASE);
>>> -		vhost_vring_call_split(dev, vq);
>>> -	} else
>>> -		vq->last_async_desc_idx += n_descs;
>>> +			vhost_vring_call_packed(dev, vq);
>>> +		} else {
>>> +			write_back_completed_descs_split(vq, n_descs);
>>> +
>>> +			__atomic_add_fetch(&vq->used->idx, n_descs,
>>> +					__ATOMIC_RELEASE);
>>> +			vhost_vring_call_split(dev, vq);
>>> +		}
>>> +	} else {
>>> +		if (vq_is_packed(dev))
>>> +			vq->last_async_buffer_idx += n_buffers;
>>> +		else
>>> +			vq->last_async_desc_idx += n_descs;
>>> +	}
>>>
>>>  done:
>>>  	rte_spinlock_unlock(&vq->access_lock);
>>> @@ -1795,9 +2198,10 @@ virtio_dev_rx_async_submit(struct virtio_net
>> *dev, uint16_t queue_id,
>>>  	if (count == 0)
>>>  		goto out;
>>>
>>> -	/* TODO: packed queue not implemented */
>>>  	if (vq_is_packed(dev))
>>> -		nb_tx = 0;
>>> +		nb_tx = virtio_dev_rx_async_submit_packed(dev,
>>> +				vq, queue_id, pkts, count, comp_pkts,
>>> +				comp_count);
>>>  	else
>>>  		nb_tx = virtio_dev_rx_async_submit_split(dev,
>>>  				vq, queue_id, pkts, count, comp_pkts,
>>>
>