Extend the XDP Tx metadata framework so that user can requests launch time hardware offload, where the Ethernet device will schedule the packet for transmission at a pre-determined time called launch time. The value of launch time is communicated from user space to Ethernet driver via launch_time field of struct xsk_tx_metadata.
Suggested-by: Stanislav Fomichev sdf@fomichev.me Acked-by: Stanislav Fomichev sdf@fomichev.me Signed-off-by: Song Yoong Siang yoong.siang.song@intel.com --- Documentation/netlink/specs/netdev.yaml | 4 ++ Documentation/networking/xsk-tx-metadata.rst | 62 ++++++++++++++++++++ include/net/xdp_sock.h | 10 ++++ include/net/xdp_sock_drv.h | 1 + include/uapi/linux/if_xdp.h | 10 ++++ include/uapi/linux/netdev.h | 3 + net/core/netdev-genl.c | 2 + net/xdp/xsk.c | 3 + tools/include/uapi/linux/if_xdp.h | 10 ++++ tools/include/uapi/linux/netdev.h | 3 + 10 files changed, 108 insertions(+)
diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml index cbb544bd6c84..901b5afb3df0 100644 --- a/Documentation/netlink/specs/netdev.yaml +++ b/Documentation/netlink/specs/netdev.yaml @@ -70,6 +70,10 @@ definitions: name: tx-checksum doc: L3 checksum HW offload is supported by the driver. + - + name: tx-launch-time-fifo + doc: + Launch time HW offload is supported by the driver. - name: queue-type type: enum diff --git a/Documentation/networking/xsk-tx-metadata.rst b/Documentation/networking/xsk-tx-metadata.rst index e76b0cfc32f7..df53a10ccac3 100644 --- a/Documentation/networking/xsk-tx-metadata.rst +++ b/Documentation/networking/xsk-tx-metadata.rst @@ -50,6 +50,10 @@ The flags field enables the particular offload: checksum. ``csum_start`` specifies byte offset of where the checksumming should start and ``csum_offset`` specifies byte offset where the device should store the computed checksum. +- ``XDP_TXMD_FLAGS_LAUNCH_TIME``: requests the device to schedule the + packet for transmission at a pre-determined time called launch time. The + value of launch time is indicated by ``launch_time`` field of + ``union xsk_tx_metadata``.
Besides the flags above, in order to trigger the offloads, the first packet's ``struct xdp_desc`` descriptor should set ``XDP_TX_METADATA`` @@ -65,6 +69,63 @@ In this case, when running in ``XDK_COPY`` mode, the TX checksum is calculated on the CPU. Do not enable this option in production because it will negatively affect performance.
+Launch Time +=========== + +The value of the requested launch time should be based on the device's PTP +Hardware Clock (PHC) to ensure accuracy. AF_XDP takes a different data path +compared to the ETF queuing discipline, which organizes packets and delays +their transmission. Instead, AF_XDP immediately hands off the packets to +the device driver without rearranging their order or holding them prior to +transmission. Since the driver maintains FIFO behavior and does not perform +packet reordering, a packet with a launch time request will block other +packets in the same Tx Queue until it is sent. Therefore, it is recommended +to allocate separate queue for scheduling traffic that is intended for +future transmission. + +In scenarios where the launch time offload feature is disabled, the device +driver is expected to disregard the launch time request. For correct +interpretation and meaningful operation, the launch time should never be +set to a value larger than the farthest programmable time in the future +(the horizon). Different devices have different hardware limitations on the +launch time offload feature. + +stmmac driver +------------- + +For stmmac, TSO and launch time (TBS) features are mutually exclusive for +each individual Tx Queue. By default, the driver configures Tx Queue 0 to +support TSO and the rest of the Tx Queues to support TBS. The launch time +hardware offload feature can be enabled or disabled by using the tc-etf +command to call the driver's ndo_setup_tc() callback. + +The value of the launch time that is programmed in the Enhanced Normal +Transmit Descriptors is a 32-bit value, where the most significant 8 bits +represent the time in seconds and the remaining 24 bits represent the time +in 256 ns increments. The programmed launch time is compared against the +PTP time (bits[39:8]) and rolls over after 256 seconds. Therefore, the +horizon of the launch time for dwmac4 and dwxlgmac2 is 128 seconds in the +future. + +igc driver +---------- + +For igc, all four Tx Queues support the launch time feature. The launch +time hardware offload feature can be enabled or disabled by using the +tc-etf command to call the driver's ndo_setup_tc() callback. When entering +TSN mode, the igc driver will reset the device and create a default Qbv +schedule with a 1-second cycle time, with all Tx Queues open at all times. + +The value of the launch time that is programmed in the Advanced Transmit +Context Descriptor is a relative offset to the starting time of the Qbv +transmission window of the queue. The Frst flag of the descriptor can be +set to schedule the packet for the next Qbv cycle. Therefore, the horizon +of the launch time for i225 and i226 is the ending time of the next cycle +of the Qbv transmission window of the queue. For example, when the Qbv +cycle time is set to 1 second, the horizon of the launch time ranges +from 1 second to 2 seconds, depending on where the Qbv cycle is currently +running. + Querying Device Capabilities ============================
@@ -74,6 +135,7 @@ Refer to ``xsk-flags`` features bitmask in
- ``tx-timestamp``: device supports ``XDP_TXMD_FLAGS_TIMESTAMP`` - ``tx-checksum``: device supports ``XDP_TXMD_FLAGS_CHECKSUM`` +- ``tx-launch-time-fifo``: device supports ``XDP_TXMD_FLAGS_LAUNCH_TIME``
See ``tools/net/ynl/samples/netdev.c`` on how to query this information.
diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h index bfe625b55d55..a58ae7589d12 100644 --- a/include/net/xdp_sock.h +++ b/include/net/xdp_sock.h @@ -110,11 +110,16 @@ struct xdp_sock { * indicates position where checksumming should start. * csum_offset indicates position where checksum should be stored. * + * void (*tmo_request_launch_time)(u64 launch_time, void *priv) + * Called when AF_XDP frame requested launch time HW offload support. + * launch_time indicates the PTP time at which the device can schedule the + * packet for transmission. */ struct xsk_tx_metadata_ops { void (*tmo_request_timestamp)(void *priv); u64 (*tmo_fill_timestamp)(void *priv); void (*tmo_request_checksum)(u16 csum_start, u16 csum_offset, void *priv); + void (*tmo_request_launch_time)(u64 launch_time, void *priv); };
#ifdef CONFIG_XDP_SOCKETS @@ -162,6 +167,11 @@ static inline void xsk_tx_metadata_request(const struct xsk_tx_metadata *meta, if (!meta) return;
+ if (ops->tmo_request_launch_time) + if (meta->flags & XDP_TXMD_FLAGS_LAUNCH_TIME) + ops->tmo_request_launch_time(meta->request.launch_time, + priv); + if (ops->tmo_request_timestamp) if (meta->flags & XDP_TXMD_FLAGS_TIMESTAMP) ops->tmo_request_timestamp(priv); diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h index 784cd34f5bba..fe4afb251719 100644 --- a/include/net/xdp_sock_drv.h +++ b/include/net/xdp_sock_drv.h @@ -199,6 +199,7 @@ static inline void *xsk_buff_raw_get_data(struct xsk_buff_pool *pool, u64 addr) #define XDP_TXMD_FLAGS_VALID ( \ XDP_TXMD_FLAGS_TIMESTAMP | \ XDP_TXMD_FLAGS_CHECKSUM | \ + XDP_TXMD_FLAGS_LAUNCH_TIME | \ 0)
static inline bool diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h index 42ec5ddaab8d..42869770776e 100644 --- a/include/uapi/linux/if_xdp.h +++ b/include/uapi/linux/if_xdp.h @@ -127,6 +127,12 @@ struct xdp_options { */ #define XDP_TXMD_FLAGS_CHECKSUM (1 << 1)
+/* Request launch time hardware offload. The device will schedule the packet for + * transmission at a pre-determined time called launch time. The value of + * launch time is communicated via launch_time field of struct xsk_tx_metadata. + */ +#define XDP_TXMD_FLAGS_LAUNCH_TIME (1 << 2) + /* AF_XDP offloads request. 'request' union member is consumed by the driver * when the packet is being transmitted. 'completion' union member is * filled by the driver when the transmit completion arrives. @@ -142,6 +148,10 @@ struct xsk_tx_metadata { __u16 csum_start; /* Offset from csum_start where checksum should be stored. */ __u16 csum_offset; + + /* XDP_TXMD_FLAGS_LAUNCH_TIME */ + /* Launch time in nanosecond against the PTP HW Clock */ + __u64 launch_time; } request;
struct { diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h index e4be227d3ad6..aac92afa917e 100644 --- a/include/uapi/linux/netdev.h +++ b/include/uapi/linux/netdev.h @@ -59,10 +59,13 @@ enum netdev_xdp_rx_metadata { * by the driver. * @NETDEV_XSK_FLAGS_TX_CHECKSUM: L3 checksum HW offload is supported by the * driver. + * @NETDEV_XSK_FLAGS_TX_LAUNCH_TIME_FIFO: Launch Time HW offload is supported + * by the driver. */ enum netdev_xsk_flags { NETDEV_XSK_FLAGS_TX_TIMESTAMP = 1, NETDEV_XSK_FLAGS_TX_CHECKSUM = 2, + NETDEV_XSK_FLAGS_TX_LAUNCH_TIME_FIFO = 4, };
enum netdev_queue_type { diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c index 715f85c6b62e..7832abc5ca6e 100644 --- a/net/core/netdev-genl.c +++ b/net/core/netdev-genl.c @@ -52,6 +52,8 @@ XDP_METADATA_KFUNC_xxx xsk_features |= NETDEV_XSK_FLAGS_TX_TIMESTAMP; if (netdev->xsk_tx_metadata_ops->tmo_request_checksum) xsk_features |= NETDEV_XSK_FLAGS_TX_CHECKSUM; + if (netdev->xsk_tx_metadata_ops->tmo_request_launch_time) + xsk_features |= NETDEV_XSK_FLAGS_TX_LAUNCH_TIME_FIFO; }
if (nla_put_u32(rsp, NETDEV_A_DEV_IFINDEX, netdev->ifindex) || diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 89d2bef96469..41093ea63700 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -742,6 +742,9 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, goto free_err; } } + + if (meta->flags & XDP_TXMD_FLAGS_LAUNCH_TIME) + skb->skb_mstamp_ns = meta->request.launch_time; } }
diff --git a/tools/include/uapi/linux/if_xdp.h b/tools/include/uapi/linux/if_xdp.h index 42ec5ddaab8d..42869770776e 100644 --- a/tools/include/uapi/linux/if_xdp.h +++ b/tools/include/uapi/linux/if_xdp.h @@ -127,6 +127,12 @@ struct xdp_options { */ #define XDP_TXMD_FLAGS_CHECKSUM (1 << 1)
+/* Request launch time hardware offload. The device will schedule the packet for + * transmission at a pre-determined time called launch time. The value of + * launch time is communicated via launch_time field of struct xsk_tx_metadata. + */ +#define XDP_TXMD_FLAGS_LAUNCH_TIME (1 << 2) + /* AF_XDP offloads request. 'request' union member is consumed by the driver * when the packet is being transmitted. 'completion' union member is * filled by the driver when the transmit completion arrives. @@ -142,6 +148,10 @@ struct xsk_tx_metadata { __u16 csum_start; /* Offset from csum_start where checksum should be stored. */ __u16 csum_offset; + + /* XDP_TXMD_FLAGS_LAUNCH_TIME */ + /* Launch time in nanosecond against the PTP HW Clock */ + __u64 launch_time; } request;
struct { diff --git a/tools/include/uapi/linux/netdev.h b/tools/include/uapi/linux/netdev.h index e4be227d3ad6..aac92afa917e 100644 --- a/tools/include/uapi/linux/netdev.h +++ b/tools/include/uapi/linux/netdev.h @@ -59,10 +59,13 @@ enum netdev_xdp_rx_metadata { * by the driver. * @NETDEV_XSK_FLAGS_TX_CHECKSUM: L3 checksum HW offload is supported by the * driver. + * @NETDEV_XSK_FLAGS_TX_LAUNCH_TIME_FIFO: Launch Time HW offload is supported + * by the driver. */ enum netdev_xsk_flags { NETDEV_XSK_FLAGS_TX_TIMESTAMP = 1, NETDEV_XSK_FLAGS_TX_CHECKSUM = 2, + NETDEV_XSK_FLAGS_TX_LAUNCH_TIME_FIFO = 4, };
enum netdev_queue_type {