netdev - [RFC PATCH v2 02/15] vhost/vsock: non-linear skb handling support

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Date:   Sun, 23 Apr 2023 22:26:30 +0300
From:   Arseniy Krasnov <AVKrasnov@...rdevices.ru>
To:     Stefan Hajnoczi <stefanha@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Bobby Eshleman <bobby.eshleman@...edance.com>
CC:     <kvm@...r.kernel.org>, <virtualization@...ts.linux-foundation.org>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <kernel@...rdevices.ru>, <oxffffaa@...il.com>,
        <avkrasnov@...rdevices.ru>,
        Arseniy Krasnov <AVKrasnov@...rdevices.ru>
Subject: [RFC PATCH v2 02/15] vhost/vsock: non-linear skb handling support

This adds copying to guest's virtio buffers from non-linear skbs. Such
skbs are created by protocol layer when MSG_ZEROCOPY flags is used.

Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
---
 drivers/vhost/vsock.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 6578db78f0ae..1e70aa390e44 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -197,11 +197,20 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 			break;
 		}
 
-		nbytes = copy_to_iter(skb->data, payload_len, &iov_iter);
-		if (nbytes != payload_len) {
-			kfree_skb(skb);
-			vq_err(vq, "Faulted on copying pkt buf\n");
-			break;
+		if (skb_is_nonlinear(skb)) {
+			if (virtio_transport_nl_skb_to_iov(skb, &iov_iter,
+							   payload_len,
+							   false)) {
+				vq_err(vq, "Faulted on copying pkt buf from page\n");
+				break;
+			}
+		} else {
+			nbytes = copy_to_iter(skb->data, payload_len, &iov_iter);
+			if (nbytes != payload_len) {
+				kfree_skb(skb);
+				vq_err(vq, "Faulted on copying pkt buf\n");
+				break;
+			}
 		}
 
 		/* Deliver to monitoring devices all packets that we
@@ -212,7 +221,9 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 		vhost_add_used(vq, head, sizeof(*hdr) + payload_len);
 		added = true;
 
-		skb_pull(skb, payload_len);
+		if (!skb_is_nonlinear(skb))
+			skb_pull(skb, payload_len);
+
 		total_len += payload_len;
 
 		/* If we didn't send all the payload we can requeue the packet
-- 
2.25.1