Re: [PATCH 2/5] VSOCK: support fill data to mergeable rx buffer in host

[Jason Wang <jasowang@redhat.com>]

On 2018/11/5 下午3:45, jiangyiwen wrote:
> When vhost support VIRTIO_VSOCK_F_MRG_RXBUF feature,
> it will merge big packet into rx vq.
>
> Signed-off-by: Yiwen Jiang <jiangyiwen@huawei.com>
> ---
>   drivers/vhost/vsock.c             | 117 +++++++++++++++++++++++++++++++-------
>   include/linux/virtio_vsock.h      |   1 +
>   include/uapi/linux/virtio_vsock.h |   5 ++
>   3 files changed, 102 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index 34bc3ab..648be39 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -22,7 +22,8 @@
>   #define VHOST_VSOCK_DEFAULT_HOST_CID	2
>
>   enum {
> -	VHOST_VSOCK_FEATURES = VHOST_FEATURES,
> +	VHOST_VSOCK_FEATURES = VHOST_FEATURES |
> +			(1ULL << VIRTIO_VSOCK_F_MRG_RXBUF),
>   };
>
>   /* Used to track all the vhost_vsock instances on the system. */
> @@ -80,6 +81,68 @@ static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
>   	return vsock;
>   }
>
> +static int get_rx_bufs(struct vhost_virtqueue *vq,
> +		struct vring_used_elem *heads, int datalen,
> +		unsigned *iovcount, unsigned int quota)
> +{
> +	unsigned int out, in;
> +	int seg = 0;
> +	int headcount = 0;
> +	unsigned d;
> +	int ret;
> +	/*
> +	 * len is always initialized before use since we are always called with
> +	 * datalen > 0.
> +	 */
> +	u32 uninitialized_var(len);
> +
> +	while (datalen > 0 && headcount < quota) {
> +		if (unlikely(seg >= UIO_MAXIOV)) {
> +			ret = -ENOBUFS;
> +			goto err;
> +		}
> +
> +		ret = vhost_get_vq_desc(vq, vq->iov + seg,
> +				ARRAY_SIZE(vq->iov) - seg, &out,
> +				&in, NULL, NULL);
> +		if (unlikely(ret < 0))
> +			goto err;
> +
> +		d = ret;
> +		if (d == vq->num) {
> +			ret = 0;
> +			goto err;
> +		}
> +
> +		if (unlikely(out || in <= 0)) {
> +			vq_err(vq, "unexpected descriptor format for RX: "
> +					"out %d, in %d\n", out, in);
> +			ret = -EINVAL;
> +			goto err;
> +		}
> +
> +		heads[headcount].id = cpu_to_vhost32(vq, d);
> +		len = iov_length(vq->iov + seg, in);
> +		heads[headcount].len = cpu_to_vhost32(vq, len);
> +		datalen -= len;
> +		++headcount;
> +		seg += in;
> +	}
> +
> +	heads[headcount - 1].len = cpu_to_vhost32(vq, len + datalen);
> +	*iovcount = seg;
> +
> +	/* Detect overrun */
> +	if (unlikely(datalen > 0)) {
> +		ret = UIO_MAXIOV + 1;
> +		goto err;
> +	}
> +	return headcount;
> +err:
> +	vhost_discard_vq_desc(vq, headcount);
> +	return ret;
> +}


Seems duplicated with the one used by vhost-net.

In packed virtqueue implementation, I plan to move this to vhost.c.


> +
>   static void
>   vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
>   			    struct vhost_virtqueue *vq)
> @@ -87,22 +150,34 @@ static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
>   	struct vhost_virtqueue *tx_vq = &vsock->vqs[VSOCK_VQ_TX];
>   	bool added = false;
>   	bool restart_tx = false;
> +	int mergeable;
> +	size_t vsock_hlen;
>
>   	mutex_lock(&vq->mutex);
>
>   	if (!vq->private_data)
>   		goto out;
>
> +	mergeable = vhost_has_feature(vq, VIRTIO_VSOCK_F_MRG_RXBUF);
> +	/*
> +	 * Guest fill page for rx vq in mergeable case, so it will not
> +	 * allocate pkt structure, we should reserve size of pkt in advance.
> +	 */
> +	if (likely(mergeable))
> +		vsock_hlen = sizeof(struct virtio_vsock_pkt);
> +	else
> +		vsock_hlen = sizeof(struct virtio_vsock_hdr);
> +
>   	/* Avoid further vmexits, we're already processing the virtqueue */
>   	vhost_disable_notify(&vsock->dev, vq);
>
>   	for (;;) {
>   		struct virtio_vsock_pkt *pkt;
>   		struct iov_iter iov_iter;
> -		unsigned out, in;
> +		unsigned out = 0, in = 0;
>   		size_t nbytes;
>   		size_t len;
> -		int head;
> +		s16 headcount;
>
>   		spin_lock_bh(&vsock->send_pkt_list_lock);
>   		if (list_empty(&vsock->send_pkt_list)) {
> @@ -116,16 +191,9 @@ static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
>   		list_del_init(&pkt->list);
>   		spin_unlock_bh(&vsock->send_pkt_list_lock);
>
> -		head = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
> -					 &out, &in, NULL, NULL);
> -		if (head < 0) {
> -			spin_lock_bh(&vsock->send_pkt_list_lock);
> -			list_add(&pkt->list, &vsock->send_pkt_list);
> -			spin_unlock_bh(&vsock->send_pkt_list_lock);
> -			break;
> -		}
> -
> -		if (head == vq->num) {
> +		headcount = get_rx_bufs(vq, vq->heads, vsock_hlen + pkt->len,
> +				&in, likely(mergeable) ? UIO_MAXIOV : 1);
> +		if (headcount <= 0) {
>   			spin_lock_bh(&vsock->send_pkt_list_lock);
>   			list_add(&pkt->list, &vsock->send_pkt_list);
>   			spin_unlock_bh(&vsock->send_pkt_list_lock);
> @@ -133,19 +201,13 @@ static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
>   			/* We cannot finish yet if more buffers snuck in while
>   			 * re-enabling notify.
>   			 */
> -			if (unlikely(vhost_enable_notify(&vsock->dev, vq))) {
> +			if (!headcount && unlikely(vhost_enable_notify(&vsock->dev, vq))) {
>   				vhost_disable_notify(&vsock->dev, vq);
>   				continue;
>   			}
>   			break;
>   		}
>
> -		if (out) {
> -			virtio_transport_free_pkt(pkt);
> -			vq_err(vq, "Expected 0 output buffers, got %u\n", out);
> -			break;
> -		}
> -
>   		len = iov_length(&vq->iov[out], in);
>   		iov_iter_init(&iov_iter, READ, &vq->iov[out], in, len);
>
> @@ -156,6 +218,19 @@ static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
>   			break;
>   		}
>
> +		if (likely(mergeable)) {
> +			pkt->mrg_rxbuf_hdr.num_buffers = cpu_to_le16(headcount);
> +			nbytes = copy_to_iter(&pkt->mrg_rxbuf_hdr,
> +					sizeof(pkt->mrg_rxbuf_hdr), &iov_iter);
> +			if (nbytes != sizeof(pkt->mrg_rxbuf_hdr)) {
> +				virtio_transport_free_pkt(pkt);
> +				vq_err(vq, "Faulted on copying rxbuf hdr\n");
> +				break;
> +			}
> +			iov_iter_advance(&iov_iter, (vsock_hlen -
> +					sizeof(pkt->mrg_rxbuf_hdr) - sizeof(pkt->hdr)));
> +		}
> +
>   		nbytes = copy_to_iter(pkt->buf, pkt->len, &iov_iter);
>   		if (nbytes != pkt->len) {
>   			virtio_transport_free_pkt(pkt);
> @@ -163,7 +238,7 @@ static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
>   			break;
>   		}
>
> -		vhost_add_used(vq, head, sizeof(pkt->hdr) + pkt->len);
> +		vhost_add_used_n(vq, vq->heads, headcount);
>   		added = true;


Looks rather similar to vhost-net mergeable rx buffer implementation. 
Another proof of using vhost-net.

Thanks


>
>   		if (pkt->reply) {
> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> index bf84418..da9e1fe 100644
> --- a/include/linux/virtio_vsock.h
> +++ b/include/linux/virtio_vsock.h
> @@ -50,6 +50,7 @@ struct virtio_vsock_sock {
>
>   struct virtio_vsock_pkt {
>   	struct virtio_vsock_hdr	hdr;
> +	struct virtio_vsock_mrg_rxbuf_hdr mrg_rxbuf_hdr;
>   	struct work_struct work;
>   	struct list_head list;
>   	/* socket refcnt not held, only use for cancellation */
> diff --git a/include/uapi/linux/virtio_vsock.h b/include/uapi/linux/virtio_vsock.h
> index 1d57ed3..2292f30 100644
> --- a/include/uapi/linux/virtio_vsock.h
> +++ b/include/uapi/linux/virtio_vsock.h
> @@ -63,6 +63,11 @@ struct virtio_vsock_hdr {
>   	__le32	fwd_cnt;
>   } __attribute__((packed));
>
> +/* It add mergeable rx buffers feature */
> +struct virtio_vsock_mrg_rxbuf_hdr {
> +	__le16  num_buffers;    /* number of mergeable rx buffers */
> +} __attribute__((packed));
> +
>   enum virtio_vsock_type {
>   	VIRTIO_VSOCK_TYPE_STREAM = 1,
>   };