[PATCH v2] vsock/virtio: rework MSG_ZEROCOPY flag handling
From: Arseniy Krasnov <hidden>
Date: 2026-06-14 17:48:23
Also in:
kvm, lkml, virtualization
Subsystem:
networking [general], the rest, virtio and vhost vsock driver, virtio core, vm sockets (af_vsock) · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Stefan Hajnoczi, Stefano Garzarella, "Michael S. Tsirkin", Jason Wang
Logically it was based on TCP implementation, so make further support easier, rewrite it in the TCP way. Signed-off-by: Arseniy Krasnov <redacted> --- Changelog v1->v2: * Rebase on last 'net-next'. Don't need 'skb_zcopy_set()' now - it was already added. net/vmw_vsock/virtio_transport_common.c | 48 ++++++++++++------------- 1 file changed, 23 insertions(+), 25 deletions(-)
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 09475007165b..787524b8cb44 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c@@ -328,38 +328,36 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW) return pkt_len; - if (info->msg) { - /* If zerocopy is not enabled by 'setsockopt()', we behave as - * there is no MSG_ZEROCOPY flag set. + if (info->msg && (info->msg->msg_flags & MSG_ZEROCOPY)) { + /* If 'info->msg' is not NULL, this is only VIRTIO_VSOCK_OP_RW. + * 'MSG_ZEROCOPY' flag handling here is based on the same flag + * handling from 'tcp_sendmsg_locked()'. */ - if (!sock_flag(sk_vsock(vsk), SOCK_ZEROCOPY)) - info->msg->msg_flags &= ~MSG_ZEROCOPY; + if (info->msg->msg_ubuf) { + uarg = info->msg->msg_ubuf; + can_zcopy = virtio_transport_can_zcopy(t_ops, info, pkt_len); + } else if (sock_flag(sk_vsock(vsk), SOCK_ZEROCOPY)) { + uarg = msg_zerocopy_realloc(sk_vsock(vsk), pkt_len, + NULL, false); + if (!uarg) { + virtio_transport_put_credit(vvs, pkt_len); + return -ENOMEM; + } - if (info->msg->msg_flags & MSG_ZEROCOPY) can_zcopy = virtio_transport_can_zcopy(t_ops, info, pkt_len); + if (!can_zcopy) + uarg_to_msgzc(uarg)->zerocopy = 0; + + have_uref = true; + } + + /* 'can_zcopy' means that this transmission will be + * in zerocopy way (e.g. using 'frags' array). + */ if (can_zcopy) max_skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE, (MAX_SKB_FRAGS * PAGE_SIZE)); - - if (info->msg->msg_flags & MSG_ZEROCOPY && - info->op == VIRTIO_VSOCK_OP_RW) { - uarg = info->msg->msg_ubuf; - - if (!uarg) { - uarg = msg_zerocopy_realloc(sk_vsock(vsk), - pkt_len, NULL, false); - if (!uarg) { - virtio_transport_put_credit(vvs, pkt_len); - return -ENOMEM; - } - - if (!can_zcopy) - uarg_to_msgzc(uarg)->zerocopy = 0; - - have_uref = true; - } - } } rest_len = pkt_len;
--
2.25.1