linux-kernel - Re: [RFC PATCH 3/5] vsock/virtio: can_msgzerocopy adapts to multi-devices

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Date: Thu, 23 May 2024 12:44:20 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Xuewei Niu <niuxuewei97@...il.com>
Cc: stefanha@...hat.com, mst@...hat.com, davem@...emloft.net, 
	kvm@...r.kernel.org, virtualization@...ts.linux.dev, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Xuewei Niu <niuxuewei.nxw@...group.com>
Subject: Re: [RFC PATCH 3/5] vsock/virtio: can_msgzerocopy adapts to
 multi-devices

On Fri, May 17, 2024 at 10:46:05PM GMT, Xuewei Niu wrote:
>Adds a new argument, named "cid", to let them know which `virtio_vsock` to
>be selected.
>
>Signed-off-by: Xuewei Niu <niuxuewei.nxw@...group.com>
>---
> include/linux/virtio_vsock.h            | 2 +-
> net/vmw_vsock/virtio_transport.c        | 5 ++---
> net/vmw_vsock/virtio_transport_common.c | 6 +++---
> 3 files changed, 6 insertions(+), 7 deletions(-)

Every commit in linux must be working to support bisection. So these 
changes should be made before adding multi-device support.

>
>diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>index c82089dee0c8..21bfd5e0c2e7 100644
>--- a/include/linux/virtio_vsock.h
>+++ b/include/linux/virtio_vsock.h
>@@ -168,7 +168,7 @@ struct virtio_transport {
> 	 * extra checks and can perform zerocopy transmission by
> 	 * default.
> 	 */
>-	bool (*can_msgzerocopy)(int bufs_num);
>+	bool (*can_msgzerocopy)(u32 cid, int bufs_num);
> };
>
> ssize_t
>diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>index 93d25aeafb83..998b22e5ce36 100644
>--- a/net/vmw_vsock/virtio_transport.c
>+++ b/net/vmw_vsock/virtio_transport.c
>@@ -521,14 +521,13 @@ static void virtio_vsock_rx_done(struct virtqueue *vq)
> 	queue_work(virtio_vsock_workqueue, &vsock->rx_work);
> }
>
>-static bool virtio_transport_can_msgzerocopy(int bufs_num)
>+static bool virtio_transport_can_msgzerocopy(u32 cid, int bufs_num)
> {
> 	struct virtio_vsock *vsock;
> 	bool res = false;
>
> 	rcu_read_lock();
>-
>-	vsock = rcu_dereference(the_virtio_vsock);
>+	vsock = virtio_transport_get_virtio_vsock(cid);
> 	if (vsock) {
> 		struct virtqueue *vq = vsock->vqs[VSOCK_VQ_TX];
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index bed75a41419e..e7315d7b9af1 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -39,7 +39,7 @@ virtio_transport_get_ops(struct vsock_sock *vsk)
>
> static bool virtio_transport_can_zcopy(const struct virtio_transport *t_ops,
> 				       struct virtio_vsock_pkt_info *info,
>-				       size_t pkt_len)
>+				       size_t pkt_len, unsigned int cid)
> {
> 	struct iov_iter *iov_iter;
>
>@@ -62,7 +62,7 @@ static bool virtio_transport_can_zcopy(const struct virtio_transport *t_ops,
> 		int pages_to_send = iov_iter_npages(iov_iter, MAX_SKB_FRAGS);
>
> 		/* +1 is for packet header. */
>-		return t_ops->can_msgzerocopy(pages_to_send + 1);
>+		return t_ops->can_msgzerocopy(cid, pages_to_send + 1);
> 	}
>
> 	return true;
>@@ -375,7 +375,7 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
> 			info->msg->msg_flags &= ~MSG_ZEROCOPY;
>
> 		if (info->msg->msg_flags & MSG_ZEROCOPY)
>-			can_zcopy = virtio_transport_can_zcopy(t_ops, info, pkt_len);
>+			can_zcopy = virtio_transport_can_zcopy(t_ops, info, pkt_len, src_cid);
>
> 		if (can_zcopy)
> 			max_skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE,
>-- 
>2.34.1
>