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

[Arseny Krasnov <arseny.krasnov@kaspersky.com>]

On 03.06.2021 18:34, Stefano Garzarella wrote:
> 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?
Ack
>
>> 		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
>>
>