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

[Stefano Garzarella <sgarzare@redhat.com>]

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@kaspersky.com>
>---
> 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
>