Re: [PATCH net v2 2/2] virtio-net: xsk: rx: move the xdp->data adjustment to buf_to_xdp()
On 6/24/25 17:17, Paolo Abeni wrote:
On 6/21/25 4:49 PM, Bui Quang Minh wrote:
This commit does not do any functional changes. It moves xdp->data
adjustment for buffer other than first buffer to buf_to_xdp() helper so
that the xdp_buff adjustment does not scatter over different functions.
Signed-off-by: Bui Quang Minh
---
drivers/net/virtio_net.c | 16 ++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 1eb237cd5d0b..4e942ea1bfa3 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1159,7 +1159,19 @@ static struct xdp_buff *buf_to_xdp(struct virtnet_info
*vi,
return NULL;
}
- xsk_buff_set_size(xdp, len);
+ if (first_buf) {
+ xsk_buff_set_size(xdp, len);
+ } else {
+ /* This is the same as xsk_buff_set_size but with the adjusted
+* xdp->data.
+*/
+ xdp->data = xdp->data_hard_start + XDP_PACKET_HEADROOM;
+ xdp->data -= vi->hdr_len;
+ xdp->data_meta = xdp->data;
+ xdp->data_end = xdp->data + len;
+ xdp->flags = 0;
+ }
+
xsk_buff_dma_sync_for_cpu(xdp);
return xdp;
@@ -1284,7 +1296,7 @@ static int xsk_append_merge_buffer(struct virtnet_info
*vi,
goto err;
}
- memcpy(buf, xdp->data - vi->hdr_len, len);
+ memcpy(buf, xdp->data, len);
xsk_buff_free(xdp);
I'm unsure if this change is in the right direction because it almost
open-code the existing xsk_buff_set_size() helper - any changes there
should be reflected here, too.
I've found out that there is xdp_prepare_buff helper which gives more
control over the headroom so it can be used here. I'll update in the
next version.
Thanks,
Quang Minh.
Re: [PATCH net v2 2/2] virtio-net: xsk: rx: move the xdp->data adjustment to buf_to_xdp()
On 6/21/25 4:49 PM, Bui Quang Minh wrote:
> This commit does not do any functional changes. It moves xdp->data
> adjustment for buffer other than first buffer to buf_to_xdp() helper so
> that the xdp_buff adjustment does not scatter over different functions.
>
> Signed-off-by: Bui Quang Minh
> ---
> drivers/net/virtio_net.c | 16 ++--
> 1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 1eb237cd5d0b..4e942ea1bfa3 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1159,7 +1159,19 @@ static struct xdp_buff *buf_to_xdp(struct virtnet_info
> *vi,
> return NULL;
> }
>
> - xsk_buff_set_size(xdp, len);
> + if (first_buf) {
> + xsk_buff_set_size(xdp, len);
> + } else {
> + /* This is the same as xsk_buff_set_size but with the adjusted
> + * xdp->data.
> + */
> + xdp->data = xdp->data_hard_start + XDP_PACKET_HEADROOM;
> + xdp->data -= vi->hdr_len;
> + xdp->data_meta = xdp->data;
> + xdp->data_end = xdp->data + len;
> + xdp->flags = 0;
> + }
> +
> xsk_buff_dma_sync_for_cpu(xdp);
>
> return xdp;
> @@ -1284,7 +1296,7 @@ static int xsk_append_merge_buffer(struct virtnet_info
> *vi,
> goto err;
> }
>
> - memcpy(buf, xdp->data - vi->hdr_len, len);
> + memcpy(buf, xdp->data, len);
>
> xsk_buff_free(xdp);
>
I'm unsure if this change is in the right direction because it almost
open-code the existing xsk_buff_set_size() helper - any changes there
should be reflected here, too.
Also AFAICS xdp->data will now carry a different value, and I guess such
change is user-visible from the attached xdp program. The commit message
should at least mentions such fact.
Thanks,
Paolo
Re: [PATCH net v2 2/2] virtio-net: xsk: rx: move the xdp->data adjustment to buf_to_xdp()
On 6/24/25 17:17, Paolo Abeni wrote:
On 6/21/25 4:49 PM, Bui Quang Minh wrote:
This commit does not do any functional changes. It moves xdp->data
adjustment for buffer other than first buffer to buf_to_xdp() helper so
that the xdp_buff adjustment does not scatter over different functions.
Signed-off-by: Bui Quang Minh
---
drivers/net/virtio_net.c | 16 ++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 1eb237cd5d0b..4e942ea1bfa3 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1159,7 +1159,19 @@ static struct xdp_buff *buf_to_xdp(struct virtnet_info
*vi,
return NULL;
}
- xsk_buff_set_size(xdp, len);
+ if (first_buf) {
+ xsk_buff_set_size(xdp, len);
+ } else {
+ /* This is the same as xsk_buff_set_size but with the adjusted
+* xdp->data.
+*/
+ xdp->data = xdp->data_hard_start + XDP_PACKET_HEADROOM;
+ xdp->data -= vi->hdr_len;
+ xdp->data_meta = xdp->data;
+ xdp->data_end = xdp->data + len;
+ xdp->flags = 0;
+ }
+
xsk_buff_dma_sync_for_cpu(xdp);
return xdp;
@@ -1284,7 +1296,7 @@ static int xsk_append_merge_buffer(struct virtnet_info
*vi,
goto err;
}
- memcpy(buf, xdp->data - vi->hdr_len, len);
+ memcpy(buf, xdp->data, len);
xsk_buff_free(xdp);
I'm unsure if this change is in the right direction because it almost
open-code the existing xsk_buff_set_size() helper - any changes there
should be reflected here, too.
Also AFAICS xdp->data will now carry a different value, and I guess such
change is user-visible from the attached xdp program. The commit message
should at least mentions such fact.
The else path in buf_to_xdp is only triggered when it's called in
xsk_append_merge_buffer. That's also the reason of the memcpy line
change in xsk_append_merge_buffer. xsk_append_merge_buffer will allocate
frag and copy xdp_buff's data to that frag. Previously, after
buf_to_xdp, the xdp->data does not point to correct place yet so when
memcpy, we need to copy from xdp->data - vi->hdr_len. With this change,
we will adjust xdp->data = xdp->data - vi->hdr_len right in buf_to_xdp
and also adjust other fields (xdp->data_end) to the correct place too.
So I don't think there is a functional change in this commit.
Thanks,
Quang Minh.
Re: [PATCH net v2 2/2] virtio-net: xsk: rx: move the xdp->data adjustment to buf_to_xdp()
On Sat, 21 Jun 2025 21:49:52 +0700, Bui Quang Minh
wrote:
> This commit does not do any functional changes. It moves xdp->data
> adjustment for buffer other than first buffer to buf_to_xdp() helper so
> that the xdp_buff adjustment does not scatter over different functions.
>
> Signed-off-by: Bui Quang Minh
> ---
> drivers/net/virtio_net.c | 16 ++--
> 1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 1eb237cd5d0b..4e942ea1bfa3 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1159,7 +1159,19 @@ static struct xdp_buff *buf_to_xdp(struct virtnet_info
> *vi,
> return NULL;
> }
>
> - xsk_buff_set_size(xdp, len);
> + if (first_buf) {
> + xsk_buff_set_size(xdp, len);
> + } else {
> + /* This is the same as xsk_buff_set_size but with the adjusted
> + * xdp->data.
> + */
> + xdp->data = xdp->data_hard_start + XDP_PACKET_HEADROOM;
> + xdp->data -= vi->hdr_len;
> + xdp->data_meta = xdp->data;
> + xdp->data_end = xdp->data + len;
> + xdp->flags = 0;
> + }
> +
> xsk_buff_dma_sync_for_cpu(xdp);
>
> return xdp;
> @@ -1284,7 +1296,7 @@ static int xsk_append_merge_buffer(struct virtnet_info
> *vi,
> goto err;
> }
>
> - memcpy(buf, xdp->data - vi->hdr_len, len);
> + memcpy(buf, xdp->data, len);
>
> xsk_buff_free(xdp);
>
> --
> 2.43.0
>
Re: [PATCH net v2 2/2] virtio-net: xsk: rx: move the xdp->data adjustment to buf_to_xdp()
On Sat, 21 Jun 2025 21:49:52 +0700, Bui Quang Minh
wrote:
> This commit does not do any functional changes. It moves xdp->data
> adjustment for buffer other than first buffer to buf_to_xdp() helper so
> that the xdp_buff adjustment does not scatter over different functions.
>
> Signed-off-by: Bui Quang Minh
Reviewed-by: Xuan Zhuo
> ---
> drivers/net/virtio_net.c | 16 ++--
> 1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 1eb237cd5d0b..4e942ea1bfa3 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1159,7 +1159,19 @@ static struct xdp_buff *buf_to_xdp(struct virtnet_info
> *vi,
> return NULL;
> }
>
> - xsk_buff_set_size(xdp, len);
> + if (first_buf) {
> + xsk_buff_set_size(xdp, len);
> + } else {
> + /* This is the same as xsk_buff_set_size but with the adjusted
> + * xdp->data.
> + */
> + xdp->data = xdp->data_hard_start + XDP_PACKET_HEADROOM;
> + xdp->data -= vi->hdr_len;
> + xdp->data_meta = xdp->data;
> + xdp->data_end = xdp->data + len;
> + xdp->flags = 0;
> + }
> +
> xsk_buff_dma_sync_for_cpu(xdp);
>
> return xdp;
> @@ -1284,7 +1296,7 @@ static int xsk_append_merge_buffer(struct virtnet_info
> *vi,
> goto err;
> }
>
> - memcpy(buf, xdp->data - vi->hdr_len, len);
> + memcpy(buf, xdp->data, len);
>
> xsk_buff_free(xdp);
>
> --
> 2.43.0
>
