On 01/03/2018 02:25 AM, Jesper Dangaard Brouer wrote:
> This patch only introduce the core data structures and API functions.
> All XDP enabled drivers must use the API before this info can used.
>
> There is a need for XDP to know more about the RX-queue a given XDP
> frames have arrived on. For both the XDP bpf-prog and kernel side.
>
> Instead of extending xdp_buff each time new info is needed, the patch
> creates a separate read-mostly struct xdp_rxq_info, that contains this
> info. We stress this data/cache-line is for read-only info. This is
> NOT for dynamic per packet info, use the data_meta for such use-cases.
>
> The performance advantage is this info can be setup at RX-ring init
> time, instead of updating N-members in xdp_buff. A possible (driver
> level) micro optimization is that xdp_buff->rxq assignment could be
> done once per XDP/NAPI loop. The extra pointer deref only happens for
> program needing access to this info (thus, no slowdown to existing
> use-cases).
>
> Signed-off-by: Jesper Dangaard Brouer <bro...@redhat.com>
> ---
> include/linux/filter.h | 2 +
> include/net/xdp.h | 47 ++++++++++++++++++++++++++++++++++
> net/core/Makefile | 2 +
> net/core/xdp.c | 67
> ++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 117 insertions(+), 1 deletion(-)
> create mode 100644 include/net/xdp.h
> create mode 100644 net/core/xdp.c
>
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index 2b0df2703671..425056c7f96c 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -20,6 +20,7 @@
> #include <linux/set_memory.h>
> #include <linux/kallsyms.h>
>
> +#include <net/xdp.h>
> #include <net/sch_generic.h>
Perhaps just 'struct xdp_rxq_info' is need here instead of
the full include. At least that is the pattern used for sk_buff
and sock. (by the way sorry for the late v4 feedback)
>
> #include <uapi/linux/filter.h>
> @@ -503,6 +504,7 @@ struct xdp_buff {
> void *data_end;
> void *data_meta;
> void *data_hard_start;
> + struct xdp_rxq_info *rxq;
> };
>
> /* Compute the linear packet data range [data, data_end) which
> diff --git a/include/net/xdp.h b/include/net/xdp.h
> new file mode 100644
> index 000000000000..86c41631a908
> --- /dev/null
> +++ b/include/net/xdp.h
[...]
> +
> +/* Returns 0 on success, negative on failure */
> +int xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,
> + struct net_device *dev, u32 queue_index)
> +{
> + if (xdp_rxq->reg_state == REG_STATE_UNUSED) {
> + WARN(1, "Driver promised not to register this");
> + return -EINVAL;
> + }
> +
> + if (xdp_rxq->reg_state == REG_STATE_REGISTERED) {
> + WARN(1, "Missing unregister, handled but fix driver");
> + xdp_rxq_info_unreg(xdp_rxq);
> + }
> +
> + if (!dev) {
Seems a bit paranoid, driver passing a NULL dev would be
badly broken. And probably not important but could make
above tests unlikely().
> + WARN(1, "Missing net_device from driver");
> + return -ENODEV;
> + }
> +
> + /* State either UNREGISTERED or NEW */
> + xdp_rxq_info_init(xdp_rxq);
> + xdp_rxq->dev = dev;
> + xdp_rxq->queue_index = queue_index;
> +
> + xdp_rxq->reg_state = REG_STATE_REGISTERED;
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(xdp_rxq_info_reg);
> +
> +void xdp_rxq_info_unused(struct xdp_rxq_info *xdp_rxq)
> +{
> + xdp_rxq->reg_state = REG_STATE_UNUSED;
> +}
> +EXPORT_SYMBOL_GPL(xdp_rxq_info_unused);
>
