On Wed, Oct 29, 2025 at 4:20 PM Paolo Abeni pabeni@redhat.com wrote:
On 10/29/25 2:24 AM, Jason Wang wrote:
From: "Michael S. Tsirkin" mst@redhat.com
Changing alignment of header would mean it's no longer safe to cast a 2 byte aligned pointer between formats. Use two 16 bit fields to make it 2 byte aligned as previously.
This fixes the performance regression since commit ("virtio_net: enable gso over UDP tunnel support.") as it uses virtio_net_hdr_v1_hash_tunnel which embeds virtio_net_hdr_v1_hash. Pktgen in guest + XDP_DROP on TAP + vhost_net shows the TX PPS is recovered from 2.4Mpps to 4.45Mpps.
Fixes: 56a06bd40fab ("virtio_net: enable gso over UDP tunnel support.") Cc: stable@vger.kernel.org Signed-off-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Jason Wang jasowang@redhat.com
Whoops, I replied to the older thread before reading this one.
Acked-by: Paolo Abeni pabeni@redhat.com
I apologize, build will be broken since
commit b2284768c6b32aa224ca7d0ef0741beb434f03aa Author: Jason Wang jasowang@redhat.com Date: Wed Oct 22 11:44:21 2025 +0800
virtio-net: zero unused hash fields
I will prepare a new version.
Btw, it looks like there's an uAPI change that may break builds of the userspace:
diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h index 8bf27ab8bcb4..1db45b01532b 100644 --- a/include/uapi/linux/virtio_net.h +++ b/include/uapi/linux/virtio_net.h @@ -193,7 +193,8 @@ struct virtio_net_hdr_v1 {
struct virtio_net_hdr_v1_hash { struct virtio_net_hdr_v1 hdr; - __le32 hash_value; + __le16 hash_value_lo; + __le16 hash_value_hi;
We can have a kernel only version for this but it probably means we need a kernel only version for all the future extension of vnet header?
Thanks