Re: [PATCH v10 15/18] vhost/vsock: support SEQPACKET for transport

[Stefano Garzarella]

On Thu, May 20, 2021 at 10:19:13PM +0300, Arseny Krasnov wrote:

Please describe better the changes included in this patch in the first 
part of the commit message.

> As vhost places data in buffers of guest's rx queue, keep SEQ_EOR
> bit set only when last piece of data is copied. Otherwise we get
> sequence packets for one socket in guest's rx queue with SEQ_EOR bit
> set. Also remove ignore of non-stream type of packets, handle SEQPACKET
> feature bit.
>
> Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
> ---
> v9 -> v10:
> 1) Move 'restore_flag' handling to 'payload_len' calculation
>    block.
>
> drivers/vhost/vsock.c | 44 +++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 40 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index 5e78fb719602..63d15beaad05 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -31,7 +31,8 @@
>
> enum {
> 	VHOST_VSOCK_FEATURES = VHOST_FEATURES |
> -			       (1ULL << VIRTIO_F_ACCESS_PLATFORM)
> +			       (1ULL << VIRTIO_F_ACCESS_PLATFORM) |
> +			       (1ULL << VIRTIO_VSOCK_F_SEQPACKET)
> };
>
> enum {
> @@ -56,6 +57,7 @@ struct vhost_vsock {
> 	atomic_t queued_replies;
>
> 	u32 guest_cid;
> +	bool seqpacket_allow;
> };
>
> static u32 vhost_transport_get_local_cid(void)
> @@ -112,6 +114,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> 		size_t nbytes;
> 		size_t iov_len, payload_len;
> 		int head;
> +		bool restore_flag = false;
>
> 		spin_lock_bh(&vsock->send_pkt_list_lock);
> 		if (list_empty(&vsock->send_pkt_list)) {
> @@ -168,9 +171,15 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> 		/* If the packet is greater than the space available in the
> 		 * buffer, we split it using multiple buffers.
> 		 */
> -		if (payload_len > iov_len - sizeof(pkt->hdr))
> +		if (payload_len > iov_len - sizeof(pkt->hdr)) {
> 			payload_len = iov_len - sizeof(pkt->hdr);

Please, add a comment here to explain why we need this.

> +			if (le32_to_cpu(pkt->hdr.flags) & 
> VIRTIO_VSOCK_SEQ_EOR) {
> +				pkt->hdr.flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
> +				restore_flag = true;
> +			}
> +		}
> +
> 		/* Set the correct length in the header */
> 		pkt->hdr.len = cpu_to_le32(payload_len);
>
> @@ -181,6 +190,9 @@ vhost_transport_do_send_pkt(struct vhost_vsock 
> *vsock,
> 			break;
> 		}
>
> +		if (restore_flag)
> +			pkt->hdr.flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
> +

Maybe we can restore the flag only if we are queueing again the same 
packet, I mean in the `if (pkt->off < pkt->len) {` branch below.

What do you think?

> 		nbytes = copy_to_iter(pkt->buf + pkt->off, payload_len,
> 				      &iov_iter);
> 		if (nbytes != payload_len) {
> @@ -354,8 +366,7 @@ vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq,
> 		return NULL;
> 	}
>
> -	if (le16_to_cpu(pkt->hdr.type) == VIRTIO_VSOCK_TYPE_STREAM)
> -		pkt->len = le32_to_cpu(pkt->hdr.len);
> +	pkt->len = le32_to_cpu(pkt->hdr.len);
>
> 	/* No payload */
> 	if (!pkt->len)
> @@ -398,6 +409,8 @@ static bool vhost_vsock_more_replies(struct 
> vhost_vsock *vsock)
> 	return val < vq->num;
> }
>
> +static bool vhost_transport_seqpacket_allow(u32 remote_cid);
> +
> static struct virtio_transport vhost_transport = {
> 	.transport = {
> 		.module                   = THIS_MODULE,
> @@ -424,6 +437,10 @@ static struct virtio_transport vhost_transport = {
> 		.stream_is_active         = virtio_transport_stream_is_active,
> 		.stream_allow             = virtio_transport_stream_allow,
>
> +		.seqpacket_dequeue        = virtio_transport_seqpacket_dequeue,
> +		.seqpacket_enqueue        = virtio_transport_seqpacket_enqueue,
> +		.seqpacket_allow          = vhost_transport_seqpacket_allow,
> +
> 		.notify_poll_in           = virtio_transport_notify_poll_in,
> 		.notify_poll_out          = virtio_transport_notify_poll_out,
> 		.notify_recv_init         = virtio_transport_notify_recv_init,
> @@ -441,6 +458,22 @@ static struct virtio_transport vhost_transport = {
> 	.send_pkt = vhost_transport_send_pkt,
> };
>
> +static bool vhost_transport_seqpacket_allow(u32 remote_cid)
> +{
> +	struct vhost_vsock *vsock;
> +	bool seqpacket_allow = false;
> +
> +	rcu_read_lock();
> +	vsock = vhost_vsock_get(remote_cid);
> +
> +	if (vsock)
> +		seqpacket_allow = vsock->seqpacket_allow;
> +
> +	rcu_read_unlock();
> +
> +	return seqpacket_allow;
> +}
> +
> static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
> {
> 	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
> @@ -785,6 +818,9 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
> 			goto err;
> 	}
>
> +	if (features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET))
> +		vsock->seqpacket_allow = true;
> +
> 	for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
> 		vq = &vsock->vqs[i];
> 		mutex_lock(&vq->mutex);
> --
> 2.25.1