Re: [RFC PATCH v8 15/19] vhost/vsock: enable SEQPACKET for transport

[Stefano Garzarella]

On Tue, Apr 13, 2021 at 03:46:18PM +0300, Arseny Krasnov wrote:
> This removes:
> 1) Ignore of non-stream type of packets.
> This adds:
> 1) Handling of SEQPACKET bit: if guest sets features with this bit cleared,
>   then SOCK_SEQPACKET support will be disabled.
> 2) 'seqpacket_allow()' callback.
> 3) Handling of SEQ_EOR bit: when vhost places data in buffers of guest's
>   rx queue, keep this bit set only when last piece of data is copied.
>
> Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
> ---
> v7 -> v8:
> - This patch merged with patch which adds SEQPACKET feature bit to
>   virtio transport.
> - It now handles VIRTIO_VSOCK_SEQ_EOR bit(see commit msg).
>
> drivers/vhost/vsock.c | 31 ++++++++++++++++++++++++++++---
> 1 file changed, 28 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index 5e78fb719602..0969cdc87830 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 {
> @@ -112,6 +113,7 @@ 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)) {
> @@ -174,6 +176,12 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> 		/* Set the correct length in the header */
> 		pkt->hdr.len = cpu_to_le32(payload_len);
>
> +		if (pkt->off + payload_len < pkt->len &&
> +		    pkt->hdr.flags & VIRTIO_VSOCK_SEQ_EOR) {
                             ^
                            (1)
> +			pkt->hdr.flags &= ~VIRTIO_VSOCK_SEQ_EOR;
                                 ^
                                (2)
> +			restore_flag = true;
> +		}
> +
> 		nbytes = copy_to_iter(&pkt->hdr, sizeof(pkt->hdr), &iov_iter);
> 		if (nbytes != sizeof(pkt->hdr)) {
> 			virtio_transport_free_pkt(pkt);
> @@ -181,6 +189,9 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> 			break;
> 		}
>
> +		if (restore_flag)
> +			pkt->hdr.flags |= VIRTIO_VSOCK_SEQ_EOR;
                                 ^
                                (3)
In these 3 points we should use cpu_to_le32()/le32_to_cpu().

> +
> 		nbytes = copy_to_iter(pkt->buf + pkt->off, payload_len,
> 				      &iov_iter);
> 		if (nbytes != payload_len) {
> @@ -354,8 +365,7 @@ 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 +408,8 @@ static bool vhost_vsock_more_replies(struct vhost_vsock *vsock)
> 	return val < vq->num;
> }
>
> +static bool vhost_transport_seqpacket_allow(void);
> +
> static struct virtio_transport vhost_transport = {
> 	.transport = {
> 		.module                   = THIS_MODULE,
> @@ -424,6 +436,10 @@ 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,
> @@ -439,8 +455,14 @@ static struct virtio_transport vhost_transport = {
> 	},
>
> 	.send_pkt = vhost_transport_send_pkt,
> +	.seqpacket_allow = false
> };
>
> +static bool vhost_transport_seqpacket_allow(void)
> +{
> +	return vhost_transport.seqpacket_allow;
> +}

I think here it's even worse then virtio_transport.c, because there may 
be more instances with different guests and some may require the feature 
and some may not, we can't definitely save this information in struct 
virtio_transport, we should put it in `struct vhost_vsock`.

> +
> static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
> {
> 	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
> @@ -785,6 +807,9 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
> 			goto err;
> 	}
>
> +	if (features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET))
> +		vhost_transport.seqpacket_allow = true;
> +
> 	for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
> 		vq = &vsock->vqs[i];
> 		mutex_lock(&vq->mutex);
> --
> 2.25.1