On Wed, Jul 02, 2025 at 06:28:37PM +0200, Stefano Garzarella wrote:

On Tue, Jul 01, 2025 at 05:45:02PM +0100, Will Deacon wrote:

quoted

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.
Note that the vhost code already has similar logic in
vhost_vsock_alloc_skb().

Signed-off-by: Will Deacon <will@kernel.org>
---
include/linux/virtio_vsock.h     | 4 +---
net/vmw_vsock/virtio_transport.c | 4 +++-
2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 36fb3edfa403..eb6980aa19fd 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h

@@ -52,9 +52,7 @@ static inline void virtio_vsock_skb_rx_put(struct sk_buff *skb)

	u32 len;

	len = le32_to_cpu(virtio_vsock_hdr(skb)->len);
-
-	if (len > 0)
-		skb_put(skb, len);
+	skb_put(skb, len);

Since the caller is supposed to check the len, can we just pass it as
parameter?

So we can avoid the `le32_to_cpu(virtio_vsock_hdr(skb)->len)` here.

Sure, I'll do that. It means that virtio_vsock_skb_rx_put() will briefly
be a simple wrapper around skb_put() but once the non-linear handling
comes in then it becomes useful again.

Will