* [PATCH v1] vsock/virtio: rework MSG_ZEROCOPY flag handling
@ 2026-06-05 11:53 Arseniy Krasnov
2026-06-05 15:08 ` David Laight
0 siblings, 1 reply; 2+ messages in thread
From: Arseniy Krasnov @ 2026-06-05 11:53 UTC (permalink / raw)
To: Stefan Hajnoczi, Stefano Garzarella, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, Michael S. Tsirkin,
Jason Wang, Bobby Eshleman, Xuan Zhuo, Eugenio Pérez,
Simon Horman
Cc: kvm, virtualization, netdev, linux-kernel, oxffffaa, rulkc,
Arseniy Krasnov
Logically it was based on TCP implementation, so to make further
support easier, rewrite it in the TCP way.
Signed-off-by: Arseniy Krasnov <avkrasnov@rulkc.org>
---
net/vmw_vsock/virtio_transport_common.c | 64 ++++++++++++-------------
1 file changed, 32 insertions(+), 32 deletions(-)
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 2fd9eaaf5ca6..00caeeaa5590 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -73,10 +73,13 @@ static bool virtio_transport_can_zcopy(const struct virtio_transport *t_ops,
static int virtio_transport_fill_skb(struct sk_buff *skb,
struct virtio_vsock_pkt_info *info,
size_t len,
- bool zcopy)
+ bool zcopy, struct ubuf_info *uarg)
{
struct msghdr *msg = info->msg;
+ /* We have completion - attach it to 'skb'. */
+ skb_zcopy_set(skb, uarg, NULL);
+
if (zcopy)
return __zerocopy_sg_from_iter(msg, NULL, skb,
&msg->msg_iter, len, NULL);
@@ -208,7 +211,8 @@ static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *
u32 src_cid,
u32 src_port,
u32 dst_cid,
- u32 dst_port)
+ u32 dst_port,
+ struct ubuf_info *uarg)
{
struct vsock_sock *vsk;
struct sk_buff *skb;
@@ -245,7 +249,7 @@ static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *
if (info->msg && payload_len > 0) {
int err;
- err = virtio_transport_fill_skb(skb, info, payload_len, zcopy);
+ err = virtio_transport_fill_skb(skb, info, payload_len, zcopy, uarg);
if (err)
goto out;
@@ -321,38 +325,36 @@ 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;
@@ -365,14 +367,12 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
skb = virtio_transport_alloc_skb(info, skb_len, can_zcopy,
src_cid, src_port,
- dst_cid, dst_port);
+ dst_cid, dst_port, uarg);
if (!skb) {
ret = -ENOMEM;
break;
}
- skb_zcopy_set(skb, uarg, NULL);
-
virtio_transport_inc_tx_pkt(vvs, skb);
ret = t_ops->send_pkt(skb, info->net);
@@ -1178,7 +1178,7 @@ static int virtio_transport_reset_no_sock(const struct virtio_transport *t,
le64_to_cpu(hdr->dst_cid),
le32_to_cpu(hdr->dst_port),
le64_to_cpu(hdr->src_cid),
- le32_to_cpu(hdr->src_port));
+ le32_to_cpu(hdr->src_port), NULL);
if (!reply)
return -ENOMEM;
--
2.25.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v1] vsock/virtio: rework MSG_ZEROCOPY flag handling
2026-06-05 11:53 [PATCH v1] vsock/virtio: rework MSG_ZEROCOPY flag handling Arseniy Krasnov
@ 2026-06-05 15:08 ` David Laight
0 siblings, 0 replies; 2+ messages in thread
From: David Laight @ 2026-06-05 15:08 UTC (permalink / raw)
To: Arseniy Krasnov
Cc: Stefan Hajnoczi, Stefano Garzarella, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, Michael S. Tsirkin,
Jason Wang, Bobby Eshleman, Xuan Zhuo, Eugenio Pérez,
Simon Horman, kvm, virtualization, netdev, linux-kernel, oxffffaa,
rulkc
On Fri, 5 Jun 2026 14:53:14 +0300
Arseniy Krasnov <avkrasnov@rulkc.org> wrote:
> Logically it was based on TCP implementation, so to make further
> support easier, rewrite it in the TCP way.
>
> Signed-off-by: Arseniy Krasnov <avkrasnov@rulkc.org>
> ---
> net/vmw_vsock/virtio_transport_common.c | 64 ++++++++++++-------------
> 1 file changed, 32 insertions(+), 32 deletions(-)
>
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index 2fd9eaaf5ca6..00caeeaa5590 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -73,10 +73,13 @@ static bool virtio_transport_can_zcopy(const struct virtio_transport *t_ops,
> static int virtio_transport_fill_skb(struct sk_buff *skb,
> struct virtio_vsock_pkt_info *info,
> size_t len,
> - bool zcopy)
> + bool zcopy, struct ubuf_info *uarg)
> {
> struct msghdr *msg = info->msg;
>
> + /* We have completion - attach it to 'skb'. */
> + skb_zcopy_set(skb, uarg, NULL);
> +
> if (zcopy)
> return __zerocopy_sg_from_iter(msg, NULL, skb,
> &msg->msg_iter, len, NULL);
> @@ -208,7 +211,8 @@ static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *
> u32 src_cid,
> u32 src_port,
> u32 dst_cid,
> - u32 dst_port)
> + u32 dst_port,
> + struct ubuf_info *uarg)
> {
> struct vsock_sock *vsk;
> struct sk_buff *skb;
> @@ -245,7 +249,7 @@ static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *
> if (info->msg && payload_len > 0) {
> int err;
>
> - err = virtio_transport_fill_skb(skb, info, payload_len, zcopy);
> + err = virtio_transport_fill_skb(skb, info, payload_len, zcopy, uarg);
> if (err)
> goto out;
>
> @@ -321,38 +325,36 @@ 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).
> + */
I've not looked at the tcp code, but the above doesn't look right.
I don't see why msg->msg_ubuf might be non-NULL without SOCK_ZEROCOPY set.
That would give the outer code a callback when the last skb is freed but
still copy the data.
I also don't see the point of calling msg_zerocopy_realloc() to get a
callback when the last skb is freed and then setting
uarg_to_msgzc(uarg)->zerocopy = 0;
so that the callback doesn't actually do anything.
It isn't as though you 'find out' later on that you can't actually do
zerocopy.
> 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;
> @@ -365,14 +367,12 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
>
> skb = virtio_transport_alloc_skb(info, skb_len, can_zcopy,
> src_cid, src_port,
> - dst_cid, dst_port);
> + dst_cid, dst_port, uarg);
> if (!skb) {
> ret = -ENOMEM;
> break;
> }
>
> - skb_zcopy_set(skb, uarg, NULL);
Aren't you passing uarg through two function calls instead of doing it here.
Doesn't even make it clearer what is going on.
-- David
> -
> virtio_transport_inc_tx_pkt(vvs, skb);
>
> ret = t_ops->send_pkt(skb, info->net);
> @@ -1178,7 +1178,7 @@ static int virtio_transport_reset_no_sock(const struct virtio_transport *t,
> le64_to_cpu(hdr->dst_cid),
> le32_to_cpu(hdr->dst_port),
> le64_to_cpu(hdr->src_cid),
> - le32_to_cpu(hdr->src_port));
> + le32_to_cpu(hdr->src_port), NULL);
> if (!reply)
> return -ENOMEM;
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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