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[35.245.174.172]) by smtp.gmail.com with ESMTPSA id n13-20020a0ce54d000000b00637873ff0f3sm4668260qvm.15.2023.07.25.13.54.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Jul 2023 13:54:54 -0700 (PDT) Date: Tue, 25 Jul 2023 16:54:54 -0400 From: Willem de Bruijn To: Stanislav Fomichev , bpf@vger.kernel.org Message-ID: <64c0369eadbd5_3fe1bc2940@willemb.c.googlers.com.notmuch> In-Reply-To: <20230724235957.1953861-3-sdf@google.com> References: <20230724235957.1953861-1-sdf@google.com> <20230724235957.1953861-3-sdf@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Message-ID-Hash: HLDE5JS3NFHAHKDA3SO45FLVMCIEF7JO X-Message-ID-Hash: HLDE5JS3NFHAHKDA3SO45FLVMCIEF7JO X-MailFrom: willemdebruijn.kernel@gmail.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, kuba@kernel.org, toke@kernel.org, willemb@google.com, dsahern@kernel.org, magnus.karlsson@intel.com, bjorn@kernel.org, maciej.fijalkowski@intel.com, hawk@kernel.org, netdev@vger.kernel.org, xdp-hints@xdp-project.net X-Mailman-Version: 3.3.8 Precedence: list Subject: [xdp-hints] Re: [RFC net-next v4 2/8] xsk: add TX timestamp and TX checksum offload support List-Id: XDP hardware hints design discussion Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: Stanislav Fomichev wrote: > This change actually defines the (initial) metadata layout > that should be used by AF_XDP userspace (xsk_tx_metadata). > The first field is flags which requests appropriate offloads, > followed by the offload-specific fields. The supported per-device > offloads are exported via netlink (new xsk-flags). > > The offloads themselves are still implemented in a bit of a > framework-y fashion that's left from my initial kfunc attempt. > I'm introducing new xsk_tx_metadata_ops which drivers are > supposed to implement. The drivers are also supposed > to call xsk_tx_metadata_request/xsk_tx_metadata_complete in > the right places. Since xsk_tx_metadata_{request,_complete} > are static inline, we don't incur any extra overhead doing > indirect calls. > > The benefit of this scheme is as follows: > - keeps all metadata layout parsing away from driver code > - makes it easy to grep and see which drivers implement what > - don't need any extra flags to maintain to keep track of that > offloads are implemented; if the callback is implemented - the offload > is supported (used by netlink reporting code) > > Two offloads are defined right now: > 1. XDP_TX_METADATA_CHECKSUM: skb-style csum_start+csum_offset > 2. XDP_TX_METADATA_TIMESTAMP: writes TX timestamp back into metadata > area upon completion (tx_timestamp field) > > The offloads are also implemented for copy mode: > 1. Extra XDP_TX_METADATA_CHECKSUM_SW to trigger skb_checksum_help; this > might be useful as a reference implementation and for testing > 2. XDP_TX_METADATA_TIMESTAMP writes SW timestamp from the skb > destructor (note I'm reusing hwtstamps to pass metadata pointer) > > The struct is forward-compatible and can be extended in the future > by appending more fields. > > Signed-off-by: Stanislav Fomichev > --- > Documentation/netlink/specs/netdev.yaml | 19 ++++++++ > include/linux/netdevice.h | 27 +++++++++++ > include/linux/skbuff.h | 5 ++- > include/net/xdp_sock.h | 60 +++++++++++++++++++++++++ > include/net/xdp_sock_drv.h | 13 ++++++ > include/uapi/linux/if_xdp.h | 35 +++++++++++++++ > include/uapi/linux/netdev.h | 15 +++++++ > net/core/netdev-genl.c | 12 ++++- > net/xdp/xsk.c | 38 ++++++++++++++++ > net/xdp/xsk_queue.h | 2 +- > tools/include/uapi/linux/if_xdp.h | 50 ++++++++++++++++++--- > 11 files changed, 268 insertions(+), 8 deletions(-) > > diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml > index e41015310a6e..bf9c1cc32614 100644 > --- a/Documentation/netlink/specs/netdev.yaml > +++ b/Documentation/netlink/specs/netdev.yaml > @@ -42,6 +42,19 @@ name: netdev > doc: > This feature informs if netdev implements non-linear XDP buffer > support in ndo_xdp_xmit callback. > + - > + type: flags > + name: xsk-flags > + render-max: true > + entries: > + - > + name: tx-timestamp > + doc: > + HW timestamping egress packets is supported by the driver. > + - > + name: tx-checksum > + doc: > + L3 checksum HW offload is supported by the driver. > > attribute-sets: > - > @@ -68,6 +81,12 @@ name: netdev > type: u32 > checks: > min: 1 > + - > + name: xsk-features > + doc: Bitmask of enabled AF_XDP features. > + type: u64 > + enum: xsk-flags > + enum-as-flags: true > > operations: > list: > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h > index 11652e464f5d..8b40c80557aa 100644 > --- a/include/linux/netdevice.h > +++ b/include/linux/netdevice.h > @@ -1660,6 +1660,31 @@ struct xdp_metadata_ops { > enum xdp_rss_hash_type *rss_type); > }; > > +/* > + * This structure defines the AF_XDP TX metadata hooks for network devices. > + * The following hooks can be defined; unless noted otherwise, they are > + * optional and can be filled with a null pointer. > + * > + * int (*tmo_request_timestamp)(void *priv) > + * This function is called when AF_XDP frame requested egress timestamp. > + * > + * int (*tmo_fill_timestamp)(void *priv) > + * This function is called when AF_XDP frame, that had requested > + * egress timestamp, received a completion. The hook needs to return > + * the actual HW timestamp. > + * > + * int (*tmo_request_timestamp)(u16 csum_start, u16 csum_offset, void *priv) > + * This function is called when AF_XDP frame requested HW checksum > + * offload. csum_start indicates position where checksumming should start. > + * csum_offset indicates position where checksum should be stored. > + * > + */ > +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); > +}; > + > /** > * enum netdev_priv_flags - &struct net_device priv_flags > * > @@ -1844,6 +1869,7 @@ enum netdev_ml_priv_type { > * @netdev_ops: Includes several pointers to callbacks, > * if one wants to override the ndo_*() functions > * @xdp_metadata_ops: Includes pointers to XDP metadata callbacks. > + * @xsk_tx_metadata_ops: Includes pointers to AF_XDP TX metadata callbacks. > * @ethtool_ops: Management operations > * @l3mdev_ops: Layer 3 master device operations > * @ndisc_ops: Includes callbacks for different IPv6 neighbour > @@ -2100,6 +2126,7 @@ struct net_device { > unsigned long long priv_flags; > const struct net_device_ops *netdev_ops; > const struct xdp_metadata_ops *xdp_metadata_ops; > + const struct xsk_tx_metadata_ops *xsk_tx_metadata_ops; > int ifindex; > unsigned short gflags; > unsigned short hard_header_len; > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index faaba050f843..5febc1a5131e 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -581,7 +581,10 @@ struct skb_shared_info { > /* Warning: this field is not always filled in (UFO)! */ > unsigned short gso_segs; > struct sk_buff *frag_list; > - struct skb_shared_hwtstamps hwtstamps; > + union { > + struct skb_shared_hwtstamps hwtstamps; > + struct xsk_tx_metadata *xsk_meta; > + }; > unsigned int gso_type; > u32 tskey; > > diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h > index 467b9fb56827..288fa58c4665 100644 > --- a/include/net/xdp_sock.h > +++ b/include/net/xdp_sock.h > @@ -90,6 +90,54 @@ int xsk_generic_rcv(struct xdp_sock *xs, struct xdp_buff *xdp); > int __xsk_map_redirect(struct xdp_sock *xs, struct xdp_buff *xdp); > void __xsk_map_flush(void); > > +/** > + * xsk_tx_metadata_request - Evaluate AF_XDP TX metadata at submission > + * and call appropriate xsk_tx_metadata_ops operation. > + * @meta: pointer to AF_XDP metadata area > + * @ops: pointer to struct xsk_tx_metadata_ops > + * @priv: pointer to driver-private aread > + * > + * This function should be called by the networking device when > + * it prepares AF_XDP egress packet. > + */ > +static inline void xsk_tx_metadata_request(const struct xsk_tx_metadata *meta, > + const struct xsk_tx_metadata_ops *ops, > + void *priv) > +{ > + if (!meta) > + return; > + > + if (ops->tmo_request_timestamp) > + if (meta->flags & XDP_TX_METADATA_TIMESTAMP) > + ops->tmo_request_timestamp(priv); > + > + if (ops->tmo_request_checksum) > + if (meta->flags & XDP_TX_METADATA_CHECKSUM) > + ops->tmo_request_checksum(meta->csum_start, meta->csum_offset, priv); > +} > + > +/** > + * xsk_tx_metadata_complete - Evaluate AF_XDP TX metadata at completion > + * and call appropriate xsk_tx_metadata_ops operation. > + * @meta: pointer to AF_XDP metadata area > + * @ops: pointer to struct xsk_tx_metadata_ops > + * @priv: pointer to driver-private aread > + * > + * This function should be called by the networking device upon > + * AF_XDP egress completion. > + */ > +static inline void xsk_tx_metadata_complete(struct xsk_tx_metadata *meta, > + const struct xsk_tx_metadata_ops *ops, > + void *priv) > +{ > + if (!meta) > + return; > + > + if (ops->tmo_fill_timestamp) > + if (meta->flags & XDP_TX_METADATA_TIMESTAMP) > + meta->tx_timestamp = ops->tmo_fill_timestamp(priv); > +} > + > #else > > static inline int xsk_generic_rcv(struct xdp_sock *xs, struct xdp_buff *xdp) > @@ -106,6 +154,18 @@ static inline void __xsk_map_flush(void) > { > } > > +static inline void xsk_tx_metadata_request(struct xsk_tx_metadata *meta, > + const struct xsk_tx_metadata_ops *ops, > + void *priv) > +{ > +} > + > +static inline void xsk_tx_metadata_complete(struct xsk_tx_metadata *meta, > + const struct xsk_tx_metadata_ops *ops, > + void *priv) > +{ > +} > + > #endif /* CONFIG_XDP_SOCKETS */ > > #endif /* _LINUX_XDP_SOCK_H */ > diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h > index 1f6fc8c7a84c..e2558ac3e195 100644 > --- a/include/net/xdp_sock_drv.h > +++ b/include/net/xdp_sock_drv.h > @@ -165,6 +165,14 @@ static inline void *xsk_buff_raw_get_data(struct xsk_buff_pool *pool, u64 addr) > return xp_raw_get_data(pool, addr); > } > > +static inline struct xsk_tx_metadata *xsk_buff_get_metadata(struct xsk_buff_pool *pool, u64 addr) > +{ > + if (!pool->tx_metadata_len) > + return NULL; > + > + return xp_raw_get_data(pool, addr) - pool->tx_metadata_len; > +} > + > static inline void xsk_buff_dma_sync_for_cpu(struct xdp_buff *xdp, struct xsk_buff_pool *pool) > { > struct xdp_buff_xsk *xskb = container_of(xdp, struct xdp_buff_xsk, xdp); > @@ -324,6 +332,11 @@ static inline void *xsk_buff_raw_get_data(struct xsk_buff_pool *pool, u64 addr) > return NULL; > } > > +static inline struct xsk_tx_metadata *xsk_buff_get_metadata(struct xsk_buff_pool *pool, u64 addr) > +{ > + return NULL; > +} > + > static inline void xsk_buff_dma_sync_for_cpu(struct xdp_buff *xdp, struct xsk_buff_pool *pool) > { > } > diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h > index b37b50102e1c..b9b1b2c4108a 100644 > --- a/include/uapi/linux/if_xdp.h > +++ b/include/uapi/linux/if_xdp.h > @@ -106,6 +106,38 @@ struct xdp_options { > #define XSK_UNALIGNED_BUF_ADDR_MASK \ > ((1ULL << XSK_UNALIGNED_BUF_OFFSET_SHIFT) - 1) > > +/* Request transmit timestamp. Upon completion, put it into tx_timestamp > + * field of struct xsk_tx_metadata. > + */ > +#define XDP_TX_METADATA_TIMESTAMP (1 << 0) > + > +/* Request transmit checksum offload. Checksum start position and offset > + * are communicated via csum_start and csum_offset fields of struct > + * xsk_tx_metadata. > + */ > +#define XDP_TX_METADATA_CHECKSUM (1 << 1) > + > +/* Force checksum calculation in software. Can be used for testing or > + * working around potential HW issues. This option causes performance > + * degradation and only works in XDP_COPY mode. > + */ > +#define XDP_TX_METADATA_CHECKSUM_SW (1 << 2) > + > +struct xsk_tx_metadata { > + __u32 flags; > + > + /* XDP_TX_METADATA_CHECKSUM */ > + > + /* Offset from desc->addr where checksumming should start. */ > + __u16 csum_start; > + /* Offset from csum_start where checksum should be stored. */ > + __u16 csum_offset; > + > + /* XDP_TX_METADATA_TIMESTAMP */ > + > + __u64 tx_timestamp; > +}; > + > /* Rx/Tx descriptor */ > struct xdp_desc { > __u64 addr; > @@ -122,4 +154,7 @@ struct xdp_desc { > */ > #define XDP_PKT_CONTD (1 << 0) > > +/* TX packet carries valid metadata. */ > +#define XDP_TX_METADATA (1 << 1) > + > #endif /* _LINUX_IF_XDP_H */ > diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h > index bf71698a1e82..cf1e11c76339 100644 > --- a/include/uapi/linux/netdev.h > +++ b/include/uapi/linux/netdev.h > @@ -37,11 +37,26 @@ enum netdev_xdp_act { > NETDEV_XDP_ACT_MASK = 127, > }; > > +/** > + * enum netdev_xsk_flags > + * @NETDEV_XSK_FLAGS_TX_TIMESTAMP: HW timestamping egress packets is supported > + * by the driver. > + * @NETDEV_XSK_FLAGS_TX_CHECKSUM: L3 checksum 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_MASK = 3, > +}; > + > enum { > NETDEV_A_DEV_IFINDEX = 1, > NETDEV_A_DEV_PAD, > NETDEV_A_DEV_XDP_FEATURES, > NETDEV_A_DEV_XDP_ZC_MAX_SEGS, > + NETDEV_A_DEV_XSK_FEATURES, > > __NETDEV_A_DEV_MAX, > NETDEV_A_DEV_MAX = (__NETDEV_A_DEV_MAX - 1) > diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c > index 65ef4867fc49..9e8c1f3caf36 100644 > --- a/net/core/netdev-genl.c > +++ b/net/core/netdev-genl.c > @@ -12,15 +12,25 @@ static int > netdev_nl_dev_fill(struct net_device *netdev, struct sk_buff *rsp, > u32 portid, u32 seq, int flags, u32 cmd) > { > + u64 xsk_flags = 0; > void *hdr; > > hdr = genlmsg_put(rsp, portid, seq, &netdev_nl_family, flags, cmd); > if (!hdr) > return -EMSGSIZE; > > + if (netdev->xsk_tx_metadata_ops) { > + if (netdev->xsk_tx_metadata_ops->tmo_fill_timestamp) > + xsk_flags |= NETDEV_XSK_FLAGS_TX_TIMESTAMP; > + if (netdev->xsk_tx_metadata_ops->tmo_request_checksum) > + xsk_flags |= NETDEV_XSK_FLAGS_TX_CHECKSUM; > + } > + > if (nla_put_u32(rsp, NETDEV_A_DEV_IFINDEX, netdev->ifindex) || > nla_put_u64_64bit(rsp, NETDEV_A_DEV_XDP_FEATURES, > - netdev->xdp_features, NETDEV_A_DEV_PAD)) { > + netdev->xdp_features, NETDEV_A_DEV_PAD) || > + nla_put_u64_64bit(rsp, NETDEV_A_DEV_XSK_FEATURES, > + xsk_flags, NETDEV_A_DEV_PAD)) { > genlmsg_cancel(rsp, hdr); > return -EINVAL; > } > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c > index 81106e4d6e0f..9a5c4e63898d 100644 > --- a/net/xdp/xsk.c > +++ b/net/xdp/xsk.c > @@ -542,6 +542,15 @@ static u32 xsk_get_num_desc(struct sk_buff *skb) > > static void xsk_destruct_skb(struct sk_buff *skb) > { > + struct xsk_tx_metadata *meta = skb_shinfo(skb)->xsk_meta; > + > + if (meta) { > + if (meta->flags & XDP_TX_METADATA_TIMESTAMP) { > + /* sw completion timestamp, not a real one */ > + meta->tx_timestamp = ktime_get_tai_fast_ns(); > + } > + } > + > xsk_cq_submit_locked(xdp_sk(skb->sk), xsk_get_num_desc(skb)); > sock_wfree(skb); > } > @@ -626,6 +635,7 @@ static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs, > static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, > struct xdp_desc *desc) > { > + struct xsk_tx_metadata *meta = NULL; > struct net_device *dev = xs->dev; > struct sk_buff *skb = xs->skb; > int err; > @@ -678,12 +688,40 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, > > skb_add_rx_frag(skb, nr_frags, page, 0, len, 0); > } > + > + if (desc->options & XDP_TX_METADATA) { > + if (unlikely(xs->tx_metadata_len == 0)) { > + err = -EINVAL; > + goto free_err; > + } > + > + meta = buffer - xs->tx_metadata_len; > + > + if (meta->flags & XDP_TX_METADATA_CHECKSUM) { > + if (unlikely(meta->csum_start + meta->csum_offset + > + sizeof(__sum16) > len)) { > + err = -EINVAL; > + goto free_err; > + } > + > + skb->csum_start = hr + meta->csum_start; > + skb->csum_offset = meta->csum_offset; > + skb->ip_summed = CHECKSUM_PARTIAL; > + > + if (unlikely(meta->flags & XDP_TX_METADATA_CHECKSUM_SW)) { > + err = skb_checksum_help(skb); > + if (err) > + goto free_err; > + } > + } > + } > } > > skb->dev = dev; > skb->priority = xs->sk.sk_priority; > skb->mark = xs->sk.sk_mark; > skb->destructor = xsk_destruct_skb; > + skb_shinfo(skb)->xsk_meta = meta; > xsk_set_destructor_arg(skb); > > return skb; > diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h > index c74a1372bcb9..6f2d1621c992 100644 > --- a/net/xdp/xsk_queue.h > +++ b/net/xdp/xsk_queue.h > @@ -137,7 +137,7 @@ static inline bool xskq_cons_read_addr_unchecked(struct xsk_queue *q, u64 *addr) > > static inline bool xp_unused_options_set(u32 options) > { > - return options & ~XDP_PKT_CONTD; > + return options & ~(XDP_PKT_CONTD | XDP_TX_METADATA); > } > > static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool, > diff --git a/tools/include/uapi/linux/if_xdp.h b/tools/include/uapi/linux/if_xdp.h > index 73a47da885dc..b9b1b2c4108a 100644 > --- a/tools/include/uapi/linux/if_xdp.h > +++ b/tools/include/uapi/linux/if_xdp.h > @@ -26,11 +26,11 @@ > */ > #define XDP_USE_NEED_WAKEUP (1 << 3) > /* By setting this option, userspace application indicates that it can > - * handle multiple descriptors per packet thus enabling xsk core to split > + * handle multiple descriptors per packet thus enabling AF_XDP to split > * multi-buffer XDP frames into multiple Rx descriptors. Without this set > - * such frames will be dropped by xsk. > + * such frames will be dropped. > */ > -#define XDP_USE_SG (1 << 4) > +#define XDP_USE_SG (1 << 4) > > /* Flags for xsk_umem_config flags */ > #define XDP_UMEM_UNALIGNED_CHUNK_FLAG (1 << 0) > @@ -69,6 +69,7 @@ struct xdp_mmap_offsets { > #define XDP_UMEM_COMPLETION_RING 6 > #define XDP_STATISTICS 7 > #define XDP_OPTIONS 8 > +#define XDP_TX_METADATA_LEN 9 > > struct xdp_umem_reg { > __u64 addr; /* Start of packet data area */ > @@ -105,6 +106,38 @@ struct xdp_options { > #define XSK_UNALIGNED_BUF_ADDR_MASK \ > ((1ULL << XSK_UNALIGNED_BUF_OFFSET_SHIFT) - 1) > > +/* Request transmit timestamp. Upon completion, put it into tx_timestamp > + * field of struct xsk_tx_metadata. > + */ > +#define XDP_TX_METADATA_TIMESTAMP (1 << 0) > + > +/* Request transmit checksum offload. Checksum start position and offset > + * are communicated via csum_start and csum_offset fields of struct > + * xsk_tx_metadata. > + */ > +#define XDP_TX_METADATA_CHECKSUM (1 << 1) > + > +/* Force checksum calculation in software. Can be used for testing or > + * working around potential HW issues. This option causes performance > + * degradation and only works in XDP_COPY mode. > + */ > +#define XDP_TX_METADATA_CHECKSUM_SW (1 << 2) Not sure how useful this is, especially if only for copy mode. > +struct xsk_tx_metadata { > + __u32 flags; > + > + /* XDP_TX_METADATA_CHECKSUM */ > + > + /* Offset from desc->addr where checksumming should start. */ > + __u16 csum_start; > + /* Offset from csum_start where checksum should be stored. */ > + __u16 csum_offset; > + > + /* XDP_TX_METADATA_TIMESTAMP */ > + > + __u64 tx_timestamp; > +}; Is this structure easily extensible for future offloads, such as USO?