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From:   Arseniy Krasnov <AVKrasnov@sberdevices.ru>
To:     Stefan Hajnoczi <stefanha@redhat.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Bobby Eshleman <bobby.eshleman@bytedance.com>
CC:     <kvm@vger.kernel.org>, <virtualization@lists.linux-foundation.org>,
        <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <kernel@sberdevices.ru>, <oxffffaa@gmail.com>,
        <avkrasnov@sberdevices.ru>,
        Arseniy Krasnov <AVKrasnov@sberdevices.ru>
Subject: [RFC PATCH v2 08/15] vsock: check for MSG_ZEROCOPY support
Date:   Sun, 23 Apr 2023 22:26:36 +0300
Message-ID: <20230423192643.1537470-9-AVKrasnov@sberdevices.ru>
In-Reply-To: <20230423192643.1537470-1-AVKrasnov@sberdevices.ru>
References: <20230423192643.1537470-1-AVKrasnov@sberdevices.ru>
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This feature totally depends on transport, so if transport doesn't
support it, return error.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 include/net/af_vsock.h   | 3 +++
 net/vmw_vsock/af_vsock.c | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index 0e7504a42925..270ca54cfab8 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -177,6 +177,9 @@ struct vsock_transport {
 
 	/* Read a single skb */
 	int (*read_skb)(struct vsock_sock *, skb_read_actor_t);
+
+	/* Zero-copy. */
+	bool (*msgzerocopy_allow)(void);
 };
 
 /**** CORE ****/
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index c50d2632a75f..eac8c1affd6a 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1824,6 +1824,13 @@ static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg,
 		goto out;
 	}
 
+	if (msg->msg_flags & MSG_ZEROCOPY &&
+	    (!transport->msgzerocopy_allow ||
+	     !transport->msgzerocopy_allow())) {
+		err = -EOPNOTSUPP;
+		goto out;
+	}
+
 	/* Wait for room in the produce queue to enqueue our user's data. */
 	timeout = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
 
-- 
2.25.1