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

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Date:   Thu, 13 May 2021 15:44:37 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseny Krasnov <arseny.krasnov@...persky.com>
Cc:     Stefan Hajnoczi <stefanha@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jorgen Hansen <jhansen@...are.com>,
        Colin Ian King <colin.king@...onical.com>,
        Norbert Slusarek <nslusarek@....net>,
        Andra Paraschiv <andraprs@...zon.com>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, stsp2@...dex.ru, oxffffaa@...il.com
Subject: Re: [RFC PATCH v9 15/19] vhost/vsock: enable SEQPACKET for transport

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@...persky.com>
>---
> 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.