On Mon, Jul 14, 2025 at 04:20:57PM +0100, Will Deacon wrote:
>virtio_vsock_skb_rx_put() only calls skb_put() if the length in the
>packet header is not zero even though skb_put() handles this case
>gracefully.
>
>Remove the functionally redundant check from virtio_vsock_skb_rx_put()
>and, on the assumption that this is a worthwhile optimisation for
>handling credit messages, augment the existing length checks in
>virtio_transport_rx_work() to elide the call for zero-length payloads.
>Since the callers all have the length, extend virtio_vsock_skb_rx_put()
>to take it as an additional parameter rather than fish it back out of
>the packet header.
>
>Note that the vhost code already has similar logic in
>vhost_vsock_alloc_skb().
>
>Signed-off-by: Will Deacon <will@kernel.org>
>---
> drivers/vhost/vsock.c | 2 +-
> include/linux/virtio_vsock.h | 9 ++-------
> net/vmw_vsock/virtio_transport.c | 4 +++-
> 3 files changed, 6 insertions(+), 9 deletions(-)
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
>
>diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>index 66a0f060770e..4c4a642945eb 100644
>--- a/drivers/vhost/vsock.c
>+++ b/drivers/vhost/vsock.c
>@@ -375,7 +375,7 @@ vhost_vsock_alloc_skb(struct vhost_virtqueue *vq,
> return NULL;
> }
>
>- virtio_vsock_skb_rx_put(skb);
>+ virtio_vsock_skb_rx_put(skb, payload_len);
>
> nbytes = copy_from_iter(skb->data, payload_len, &iov_iter);
> if (nbytes != payload_len) {
>diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>index 36fb3edfa403..97465f378ade 100644
>--- a/include/linux/virtio_vsock.h
>+++ b/include/linux/virtio_vsock.h
>@@ -47,14 +47,9 @@ static inline void virtio_vsock_skb_clear_tap_delivered(struct sk_buff *skb)
> VIRTIO_VSOCK_SKB_CB(skb)->tap_delivered = false;
> }
>
>-static inline void virtio_vsock_skb_rx_put(struct sk_buff *skb)
>+static inline void virtio_vsock_skb_rx_put(struct sk_buff *skb, u32 len)
> {
>- u32 len;
>-
>- len = le32_to_cpu(virtio_vsock_hdr(skb)->len);
>-
>- if (len > 0)
>- skb_put(skb, len);
>+ skb_put(skb, len);
> }
>
> static inline struct sk_buff *virtio_vsock_alloc_skb(unsigned int size, gfp_t mask)
>diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>index bd2c6aaa1a93..1af7723669cb 100644
>--- a/net/vmw_vsock/virtio_transport.c
>+++ b/net/vmw_vsock/virtio_transport.c
>@@ -656,7 +656,9 @@ static void virtio_transport_rx_work(struct work_struct *work)
> continue;
> }
>
>- virtio_vsock_skb_rx_put(skb);
>+ if (payload_len)
>+ virtio_vsock_skb_rx_put(skb, payload_len);
>+
> virtio_transport_deliver_tap_pkt(skb);
> virtio_transport_recv_pkt(&virtio_transport, skb);
> }
>--
>2.50.0.727.gbf7dc18ff4-goog
>