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[35.245.174.172]) by smtp.gmail.com with ESMTPSA id c12-20020a05620a11ac00b00767ba88f0c9sm3913220qkk.7.2023.07.25.13.58.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Jul 2023 13:58:21 -0700 (PDT) Date: Tue, 25 Jul 2023 16:58:20 -0400 From: Willem de Bruijn To: Stanislav Fomichev , bpf@vger.kernel.org Message-ID: <64c0376cd946a_3fe1bc2947a@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: FNX4IC47BSS7HWLWQXQUZSJKAGOTCYBX X-Message-ID-Hash: FNX4IC47BSS7HWLWQXQUZSJKAGOTCYBX 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) typo: tmo_request_checksum > + * 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); > +} Might be cheaper to test the flag in the hot cacheline before dereferencing ops? Also, just add these functions to net_device_ops directly, rather than dereferencing another pointer to xsk_tx_metadata_ops?