linux-kernel - Re: [RFC PATCH v8 14/19] virtio/vsock: enable SEQPACKET for transport

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Date:   Wed, 21 Apr 2021 11:22:08 +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>,
        Andra Paraschiv <andraprs@...zon.com>,
        Colin Ian King <colin.king@...onical.com>,
        Norbert Slusarek <nslusarek@....net>,
        Jeff Vander Stoep <jeffv@...gle.com>,
        Alexander Popov <alex.popov@...ux.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 v8 14/19] virtio/vsock: enable SEQPACKET for transport

On Tue, Apr 13, 2021 at 03:45:49PM +0300, Arseny Krasnov wrote:
>This adds
>1) SEQPACKET ops for virtio transport and 'seqpacket_allow()' callback.
>2) Handling of SEQPACKET bit: guest tries to negotiate it with vhost.
>
>Signed-off-by: Arseny Krasnov <arseny.krasnov@...persky.com>
>---
>v7 -> v8:
> - This patch merged with patch which adds SEQPACKET feature bit to
>   virtio transport.
>
> net/vmw_vsock/virtio_transport.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
>diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>index 2700a63ab095..ee99bd919a12 100644
>--- a/net/vmw_vsock/virtio_transport.c
>+++ b/net/vmw_vsock/virtio_transport.c
>@@ -443,6 +443,8 @@ static void virtio_vsock_rx_done(struct virtqueue 
>*vq)
> 	queue_work(virtio_vsock_workqueue, &vsock->rx_work);
> }
>
>+static bool virtio_transport_seqpacket_allow(void);
>+
> static struct virtio_transport virtio_transport = {
> 	.transport = {
> 		.module                   = THIS_MODULE,
>@@ -469,6 +471,10 @@ static struct virtio_transport virtio_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          = virtio_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,
>@@ -483,8 +489,14 @@ static struct virtio_transport virtio_transport = {
> 	},
>
> 	.send_pkt = virtio_transport_send_pkt,
>+	.seqpacket_allow = false
> };
>
>+static bool virtio_transport_seqpacket_allow(void)
>+{
>+	return virtio_transport.seqpacket_allow;
>+}
>+
> static void virtio_transport_rx_work(struct work_struct *work)
> {
> 	struct virtio_vsock *vsock =
>@@ -612,6 +624,10 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
> 	rcu_assign_pointer(the_virtio_vsock, vsock);
>
> 	mutex_unlock(&the_virtio_vsock_mutex);
>+
>+	if (vdev->features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET))
>+		virtio_transport.seqpacket_allow = true;
>+

virtio-vsock devices can be hot-plugged and hot-unplugged, so we should 
reset virtio_transport.seqpacket_allow at every probe.

Now thinking about it more, would it be better to save this information 
in struct virtio_vsock instead of struct virtio_transport?

> 	return 0;
>
> out:
>@@ -695,6 +711,7 @@ static struct virtio_device_id id_table[] = {
> };
>
> static unsigned int features[] = {
>+	VIRTIO_VSOCK_F_SEQPACKET
> };
>
> static struct virtio_driver virtio_vsock_driver = {
>-- 
>2.25.1
>