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..4324e89a8026 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..4324e89a8026 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 {

Add launch time hardware offload request to xdp_hw_metadata. Users can configure the delta of launch time relative to HW RX-time using the "-l" argument. By default, the delta is set to 0 ns, which means the launch time is disabled. By setting the delta to a non-zero value, the launch time hardware offload feature will be enabled and requested. Additionally, users can configure the Tx Queue to be enabled with the launch time hardware offload using the "-L" argument. By default, Tx Queue 0 will be used.

Acked-by: Stanislav Fomichev sdf@fomichev.me Signed-off-by: Song Yoong Siang yoong.siang.song@intel.com --- tools/testing/selftests/bpf/xdp_hw_metadata.c | 168 +++++++++++++++++- 1 file changed, 163 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c index 6f7b15d6c6ed..3d8de0d4c96a 100644 --- a/tools/testing/selftests/bpf/xdp_hw_metadata.c +++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c @@ -13,6 +13,7 @@ * - UDP 9091 packets trigger TX reply * - TX HW timestamp is requested and reported back upon completion * - TX checksum is requested + * - TX launch time HW offload is requested for transmission */

#include <test_progs.h> @@ -37,6 +38,15 @@ #include <time.h> #include <unistd.h> #include <libgen.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <sys/ioctl.h> +#include <linux/pkt_sched.h> +#include <linux/pkt_cls.h> +#include <linux/ethtool.h> +#include <sys/socket.h> +#include <arpa/inet.h>

#include "xdp_metadata.h"

@@ -64,6 +74,18 @@ int rxq; bool skip_tx; __u64 last_hw_rx_timestamp; __u64 last_xdp_rx_timestamp; +__u64 last_launch_time; +__u64 launch_time_delta_to_hw_rx_timestamp; +int launch_time_queue; + +#define run_command(cmd, ...) \ +({ \ + char command[1024]; \ + memset(command, 0, sizeof(command)); \ + snprintf(command, sizeof(command), cmd, ##__VA_ARGS__); \ + fprintf(stderr, "Running: %s\n", command); \ + system(command); \ +})

void test__fail(void) { /* for network_helpers.c */ }

@@ -298,6 +320,12 @@ static bool complete_tx(struct xsk *xsk, clockid_t clock_id) if (meta->completion.tx_timestamp) { __u64 ref_tstamp = gettime(clock_id);

+ if (launch_time_delta_to_hw_rx_timestamp) { + print_tstamp_delta("HW Launch-time", + "HW TX-complete-time", + last_launch_time, + meta->completion.tx_timestamp); + } print_tstamp_delta("HW TX-complete-time", "User TX-complete-time", meta->completion.tx_timestamp, ref_tstamp); print_tstamp_delta("XDP RX-time", "User TX-complete-time", @@ -395,6 +423,17 @@ static void ping_pong(struct xsk *xsk, void *rx_packet, clockid_t clock_id) xsk, ntohs(udph->check), ntohs(want_csum), meta->request.csum_start, meta->request.csum_offset);

+ /* Set the value of launch time */ + if (launch_time_delta_to_hw_rx_timestamp) { + meta->flags |= XDP_TXMD_FLAGS_LAUNCH_TIME; + meta->request.launch_time = last_hw_rx_timestamp + + launch_time_delta_to_hw_rx_timestamp; + last_launch_time = meta->request.launch_time; + print_tstamp_delta("HW RX-time", "HW Launch-time", + last_hw_rx_timestamp, + meta->request.launch_time); + } + memcpy(data, rx_packet, len); /* don't share umem chunk for simplicity */ tx_desc->options |= XDP_TX_METADATA; tx_desc->len = len; @@ -407,6 +446,7 @@ static int verify_metadata(struct xsk *rx_xsk, int rxq, int server_fd, clockid_t const struct xdp_desc *rx_desc; struct pollfd fds[rxq + 1]; __u64 comp_addr; + __u64 deadline; __u64 addr; __u32 idx = 0; int ret; @@ -477,9 +517,15 @@ static int verify_metadata(struct xsk *rx_xsk, int rxq, int server_fd, clockid_t if (ret) printf("kick_tx ret=%d\n", ret);

- for (int j = 0; j < 500; j++) { + /* wait 1 second + cover launch time */ + deadline = gettime(clock_id) + + NANOSEC_PER_SEC + + launch_time_delta_to_hw_rx_timestamp; + while (true) { if (complete_tx(xsk, clock_id)) break; + if (gettime(clock_id) >= deadline) + break; usleep(10); } } @@ -608,6 +654,10 @@ static void print_usage(void) " -h Display this help and exit\n\n" " -m Enable multi-buffer XDP for larger MTU\n" " -r Don't generate AF_XDP reply (rx metadata only)\n" + " -l Delta of launch time relative to HW RX-time in ns\n" + " default: 0 ns (launch time request is disabled)\n" + " -L Tx Queue to be enabled with launch time offload\n" + " default: 0 (Tx Queue 0)\n" "Generate test packets on the other machine with:\n" " echo -n xdp | nc -u -q1 <dst_ip> 9091\n";

@@ -618,7 +668,7 @@ static void read_args(int argc, char *argv[]) { int opt;

- while ((opt = getopt(argc, argv, "chmr")) != -1) { + while ((opt = getopt(argc, argv, "chmrl:L:")) != -1) { switch (opt) { case 'c': bind_flags &= ~XDP_USE_NEED_WAKEUP; @@ -634,6 +684,12 @@ static void read_args(int argc, char *argv[]) case 'r': skip_tx = true; break; + case 'l': + launch_time_delta_to_hw_rx_timestamp = atoll(optarg); + break; + case 'L': + launch_time_queue = atoll(optarg); + break; case '?': if (isprint(optopt)) fprintf(stderr, "Unknown option: -%c\n", optopt); @@ -657,23 +713,118 @@ static void read_args(int argc, char *argv[]) error(-1, errno, "Invalid interface name"); }

+void clean_existing_configurations(void) +{ + /* Check and delete root qdisc if exists */ + if (run_command("sudo tc qdisc show dev %s | grep -q 'qdisc mqprio 8001:'", ifname) == 0) + run_command("sudo tc qdisc del dev %s root", ifname); + + /* Check and delete ingress qdisc if exists */ + if (run_command("sudo tc qdisc show dev %s | grep -q 'qdisc ingress ffff:'", ifname) == 0) + run_command("sudo tc qdisc del dev %s ingress", ifname); + + /* Check and delete ethtool filters if any exist */ + if (run_command("sudo ethtool -n %s | grep -q 'Filter:'", ifname) == 0) { + run_command("sudo ethtool -n %s | grep 'Filter:' | awk '{print $2}' | xargs -n1 sudo ethtool -N %s delete >&2", + ifname, ifname); + } +} + +#define MAX_TC 16 + int main(int argc, char *argv[]) { clockid_t clock_id = CLOCK_TAI; + struct bpf_program *prog; int server_fd = -1; + size_t map_len = 0; + size_t que_len = 0; + char *buf = NULL; + char *map = NULL; + char *que = NULL; + char *tmp = NULL; + int tc = 0; int ret; int i;

- struct bpf_program *prog; - read_args(argc, argv);

rxq = rxq_num(ifname); - printf("rxq: %d\n", rxq);

+ if (launch_time_queue >= rxq || launch_time_queue < 0) + error(1, 0, "Invalid launch_time_queue."); + + clean_existing_configurations(); + sleep(1); + + /* Enable tx and rx hardware timestamping */ hwtstamp_enable(ifname);

+ /* Prepare priority to traffic class map for tc-mqprio */ + for (i = 0; i < MAX_TC; i++) { + if (i < rxq) + tc = i; + + if (asprintf(&buf, "%d ", tc) == -1) { + printf("Failed to malloc buf for tc map.\n"); + goto free_mem; + } + + map_len += strlen(buf); + tmp = realloc(map, map_len + 1); + if (!tmp) { + printf("Failed to realloc tc map.\n"); + goto free_mem; + } + map = tmp; + strcat(map, buf); + free(buf); + buf = NULL; + } + + /* Prepare traffic class to hardware queue map for tc-mqprio */ + for (i = 0; i <= tc; i++) { + if (asprintf(&buf, "1@%d ", i) == -1) { + printf("Failed to malloc buf for tc queues.\n"); + goto free_mem; + } + + que_len += strlen(buf); + tmp = realloc(que, que_len + 1); + if (!tmp) { + printf("Failed to realloc tc queues.\n"); + goto free_mem; + } + que = tmp; + strcat(que, buf); + free(buf); + buf = NULL; + } + + /* Add mqprio qdisc */ + run_command("sudo tc qdisc add dev %s handle 8001: parent root mqprio num_tc %d map %squeues %shw 0", + ifname, tc + 1, map, que); + + /* To test launch time, send UDP packet with VLAN priority 1 to port 9091 */ + if (launch_time_delta_to_hw_rx_timestamp) { + /* Enable launch time hardware offload on launch_time_queue */ + run_command("sudo tc qdisc replace dev %s parent 8001:%d etf offload clockid CLOCK_TAI delta 500000", + ifname, launch_time_queue + 1); + sleep(1); + + /* Route incoming packet with VLAN priority 1 into launch_time_queue */ + if (run_command("sudo ethtool -N %s flow-type ether vlan 0x2000 vlan-mask 0x1FFF action %d", + ifname, launch_time_queue)) { + run_command("sudo tc qdisc add dev %s ingress", ifname); + run_command("sudo tc filter add dev %s parent ffff: protocol 802.1Q flower vlan_prio 1 hw_tc %d", + ifname, launch_time_queue); + } + + /* Enable VLAN tag stripping offload */ + run_command("sudo ethtool -K %s rxvlan on", ifname); + } + rx_xsk = malloc(sizeof(struct xsk) * rxq); if (!rx_xsk) error(1, ENOMEM, "malloc"); @@ -733,4 +884,11 @@ int main(int argc, char *argv[]) cleanup(); if (ret) error(1, -ret, "verify_metadata"); + + clean_existing_configurations(); + +free_mem: + free(buf); + free(map); + free(que); }

Refactor the code for inserting an empty frame into a new function igc_insert_empty_frame(). This change extracts the logic for inserting an empty packet from igc_xmit_frame_ring() into a separate function, allowing it to be reused in future implementations, such as the XDP zero copy transmit function.

Remove the igc_desc_unused() checking in igc_init_tx_empty_descriptor() because the number of descriptors needed is guaranteed.

Ensure that skb allocation and DMA mapping work for the empty frame, before proceeding to fill in igc_tx_buffer info, context descriptor, and data descriptor.

Rate limit the error messages for skb allocation and DMA mapping failures.

Update the comment to indicate that the 2 descriptors needed by the empty frame are already taken into consideration in igc_xmit_frame_ring().

Handle the case where the insertion of an empty frame fails and explain the reason behind this handling.

Reviewed-by: Faizal Rahim faizal.abdul.rahim@linux.intel.com Reviewed-by: Maciej Fijalkowski maciej.fijalkowski@intel.com Signed-off-by: Song Yoong Siang yoong.siang.song@intel.com --- drivers/net/ethernet/intel/igc/igc_main.c | 82 ++++++++++++++--------- 1 file changed, 50 insertions(+), 32 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c index 84307bb7313e..1bfa71545e37 100644 --- a/drivers/net/ethernet/intel/igc/igc_main.c +++ b/drivers/net/ethernet/intel/igc/igc_main.c @@ -1092,7 +1092,8 @@ static int igc_init_empty_frame(struct igc_ring *ring,

dma = dma_map_single(ring->dev, skb->data, size, DMA_TO_DEVICE); if (dma_mapping_error(ring->dev, dma)) { - netdev_err_once(ring->netdev, "Failed to map DMA for TX\n"); + net_err_ratelimited("%s: DMA mapping error for empty frame\n", + netdev_name(ring->netdev)); return -ENOMEM; }

@@ -1108,20 +1109,12 @@ static int igc_init_empty_frame(struct igc_ring *ring, return 0; }

-static int igc_init_tx_empty_descriptor(struct igc_ring *ring, - struct sk_buff *skb, - struct igc_tx_buffer *first) +static void igc_init_tx_empty_descriptor(struct igc_ring *ring, + struct sk_buff *skb, + struct igc_tx_buffer *first) { union igc_adv_tx_desc *desc; u32 cmd_type, olinfo_status; - int err; - - if (!igc_desc_unused(ring)) - return -EBUSY; - - err = igc_init_empty_frame(ring, first, skb); - if (err) - return err;

cmd_type = IGC_ADVTXD_DTYP_DATA | IGC_ADVTXD_DCMD_DEXT | IGC_ADVTXD_DCMD_IFCS | IGC_TXD_DCMD | @@ -1140,8 +1133,6 @@ static int igc_init_tx_empty_descriptor(struct igc_ring *ring, ring->next_to_use++; if (ring->next_to_use == ring->count) ring->next_to_use = 0; - - return 0; }

#define IGC_EMPTY_FRAME_SIZE 60 @@ -1567,6 +1558,40 @@ static bool igc_request_tx_tstamp(struct igc_adapter *adapter, struct sk_buff *s return false; }

+static int igc_insert_empty_frame(struct igc_ring *tx_ring) +{ + struct igc_tx_buffer *empty_info; + struct sk_buff *empty_skb; + void *data; + int ret; + + empty_info = &tx_ring->tx_buffer_info[tx_ring->next_to_use]; + empty_skb = alloc_skb(IGC_EMPTY_FRAME_SIZE, GFP_ATOMIC); + if (unlikely(!empty_skb)) { + net_err_ratelimited("%s: skb alloc error for empty frame\n", + netdev_name(tx_ring->netdev)); + return -ENOMEM; + } + + data = skb_put(empty_skb, IGC_EMPTY_FRAME_SIZE); + memset(data, 0, IGC_EMPTY_FRAME_SIZE); + + /* Prepare DMA mapping and Tx buffer information */ + ret = igc_init_empty_frame(tx_ring, empty_info, empty_skb); + if (unlikely(ret)) { + dev_kfree_skb_any(empty_skb); + return ret; + } + + /* Prepare advanced context descriptor for empty packet */ + igc_tx_ctxtdesc(tx_ring, 0, false, 0, 0, 0); + + /* Prepare advanced data descriptor for empty packet */ + igc_init_tx_empty_descriptor(tx_ring, empty_skb, empty_info); + + return 0; +} + static netdev_tx_t igc_xmit_frame_ring(struct sk_buff *skb, struct igc_ring *tx_ring) { @@ -1586,6 +1611,7 @@ static netdev_tx_t igc_xmit_frame_ring(struct sk_buff *skb, * + 1 desc for skb_headlen/IGC_MAX_DATA_PER_TXD, * + 2 desc gap to keep tail from touching head, * + 1 desc for context descriptor, + * + 2 desc for inserting an empty packet for launch time, * otherwise try next time */ for (f = 0; f < skb_shinfo(skb)->nr_frags; f++) @@ -1605,24 +1631,16 @@ static netdev_tx_t igc_xmit_frame_ring(struct sk_buff *skb, launch_time = igc_tx_launchtime(tx_ring, txtime, &first_flag, &insert_empty);

if (insert_empty) { - struct igc_tx_buffer *empty_info; - struct sk_buff *empty; - void *data; - - empty_info = &tx_ring->tx_buffer_info[tx_ring->next_to_use]; - empty = alloc_skb(IGC_EMPTY_FRAME_SIZE, GFP_ATOMIC); - if (!empty) - goto done; - - data = skb_put(empty, IGC_EMPTY_FRAME_SIZE); - memset(data, 0, IGC_EMPTY_FRAME_SIZE); - - igc_tx_ctxtdesc(tx_ring, 0, false, 0, 0, 0); - - if (igc_init_tx_empty_descriptor(tx_ring, - empty, - empty_info) < 0) - dev_kfree_skb_any(empty); + /* Reset the launch time if the required empty frame fails to + * be inserted. However, this packet is not dropped, so it + * "dirties" the current Qbv cycle. This ensures that the + * upcoming packet, which is scheduled in the next Qbv cycle, + * does not require an empty frame. This way, the launch time + * continues to function correctly despite the current failure + * to insert the empty frame. + */ + if (igc_insert_empty_frame(tx_ring)) + launch_time = 0; }

done: