Re: [RFC PATCH v9 15/19] vhost/vsock: enable SEQPACKET for transport

[Stefano Garzarella]

On Sat, May 08, 2021 at 07:36:31PM +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>
> ---
> v8 -> v9:
> 1) Move 'seqpacket_allow' to 'struct vhost_vsock'.
> 2) Use cpu_to_le32()/le32_to_cpu() to work with 'flags' of packet.
>
> drivers/vhost/vsock.c | 42 +++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 39 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index 5e78fb719602..3395b25d4a35 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)) {
> @@ -174,6 +177,12 @@ 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 &&
> +		    le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOR) {
> +			pkt->hdr.flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
> +			restore_flag = true;
> +		}

I think is better to move this code in the same block when we limit
payload_len, something like this (not tested):

		/* 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)) {
			payload_len = iov_len - sizeof(pkt->hdr);

			if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOR) {
				pkt->hdr.flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
				restore_flag = true;
			}
		}

The rest LGTM.