Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted

Pull networking updates from Jakub Kicinski:
 "Core:

   - Add dedicated kmem_cache for typical/small skb->head, avoid having
     to access struct page at kfree time, and improve memory use.

   - Introduce sysctl to set default RPS configuration for new netdevs.

   - Define Netlink protocol specification format which can be used to
     describe messages used by each family and auto-generate parsers.
     Add tools for generating kernel data structures and uAPI headers.

   - Expose all net/core sysctls inside netns.

   - Remove 4s sleep in netpoll if carrier is instantly detected on
     boot.

   - Add configurable limit of MDB entries per port, and port-vlan.

   - Continue populating drop reasons throughout the stack.

   - Retire a handful of legacy Qdiscs and classifiers.

  Protocols:

   - Support IPv4 big TCP (TSO frames larger than 64kB).

   - Add IP_LOCAL_PORT_RANGE socket option, to control local port range
     on socket by socket basis.

   - Track and report in procfs number of MPTCP sockets used.

   - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
     manager.

   - IPv6: don't check net.ipv6.route.max_size and rely on garbage
     collection to free memory (similarly to IPv4).

   - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).

   - ICMP: add per-rate limit counters.

   - Add support for user scanning requests in ieee802154.

   - Remove static WEP support.

   - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
     reporting.

   - WiFi 7 EHT channel puncturing support (client & AP).

  BPF:

   - Add a rbtree data structure following the "next-gen data structure"
     precedent set by recently added linked list, that is, by using
     kfunc + kptr instead of adding a new BPF map type.

   - Expose XDP hints via kfuncs with initial support for RX hash and
     timestamp metadata.

   - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
     better support decap on GRE tunnel devices not operating in collect
     metadata.

   - Improve x86 JIT's codegen for PROBE_MEM runtime error checks.

   - Remove the need for trace_printk_lock for bpf_trace_printk and
     bpf_trace_vprintk helpers.

   - Extend libbpf's bpf_tracing.h support for tracing arguments of
     kprobes/uprobes and syscall as a special case.

   - Significantly reduce the search time for module symbols by
     livepatch and BPF.

   - Enable cpumasks to be used as kptrs, which is useful for tracing
     programs tracking which tasks end up running on which CPUs in
     different time intervals.

   - Add support for BPF trampoline on s390x and riscv64.

   - Add capability to export the XDP features supported by the NIC.

   - Add __bpf_kfunc tag for marking kernel functions as kfuncs.

   - Add cgroup.memory=nobpf kernel parameter option to disable BPF
     memory accounting for container environments.

  Netfilter:

   - Remove the CLUSTERIP target. It has been marked as obsolete for
     years, and we still have WARN splats wrt races of the out-of-band
     /proc interface installed by this target.

   - Add 'destroy' commands to nf_tables. They are identical to the
     existing 'delete' commands, but do not return an error if the
     referenced object (set, chain, rule...) did not exist.

  Driver API:

   - Improve cpumask_local_spread() locality to help NICs set the right
     IRQ affinity on AMD platforms.

   - Separate C22 and C45 MDIO bus transactions more clearly.

   - Introduce new DCB table to control DSCP rewrite on egress.

   - Support configuration of Physical Layer Collision Avoidance (PLCA)
     Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
     shared medium Ethernet.

   - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
     preemption of low priority frames by high priority frames.

   - Add support for controlling MACSec offload using netlink SET.

   - Rework devlink instance refcounts to allow registration and
     de-registration under the instance lock. Split the code into
     multiple files, drop some of the unnecessarily granular locks and
     factor out common parts of netlink operation handling.

   - Add TX frame aggregation parameters (for USB drivers).

   - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
     messages with notifications for debug.

   - Allow offloading of UDP NEW connections via act_ct.

   - Add support for per action HW stats in TC.

   - Support hardware miss to TC action (continue processing in SW from
     a specific point in the action chain).

   - Warn if old Wireless Extension user space interface is used with
     modern cfg80211/mac80211 drivers. Do not support Wireless
     Extensions for Wi-Fi 7 devices at all. Everyone should switch to
     using nl80211 interface instead.

   - Improve the CAN bit timing configuration. Use extack to return
     error messages directly to user space, update the SJW handling,
     including the definition of a new default value that will benefit
     CAN-FD controllers, by increasing their oscillator tolerance.

  New hardware / drivers:

   - Ethernet:
      - nVidia BlueField-3 support (control traffic driver)
      - Ethernet support for imx93 SoCs
      - Motorcomm yt8531 gigabit Ethernet PHY
      - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
      - Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
      - Amlogic gxl MDIO mux

   - WiFi:
      - RealTek RTL8188EU (rtl8xxxu)
      - Qualcomm Wi-Fi 7 devices (ath12k)

   - CAN:
      - Renesas R-Car V4H

  Drivers:

   - Bluetooth:
      - Set Per Platform Antenna Gain (PPAG) for Intel controllers.

   - Ethernet NICs:
      - Intel (1G, igc):
         - support TSN / Qbv / packet scheduling features of i226 model
      - Intel (100G, ice):
         - use GNSS subsystem instead of TTY
         - multi-buffer XDP support
         - extend support for GPIO pins to E823 devices
      - nVidia/Mellanox:
         - update the shared buffer configuration on PFC commands
         - implement PTP adjphase function for HW offset control
         - TC support for Geneve and GRE with VF tunnel offload
         - more efficient crypto key management method
         - multi-port eswitch support
      - Netronome/Corigine:
         - add DCB IEEE support
         - support IPsec offloading for NFP3800
      - Freescale/NXP (enetc):
         - support XDP_REDIRECT for XDP non-linear buffers
         - improve reconfig, avoid link flap and waiting for idle
         - support MAC Merge layer
      - Other NICs:
         - sfc/ef100: add basic devlink support for ef100
         - ionic: rx_push mode operation (writing descriptors via MMIO)
         - bnxt: use the auxiliary bus abstraction for RDMA
         - r8169: disable ASPM and reset bus in case of tx timeout
         - cpsw: support QSGMII mode for J721e CPSW9G
         - cpts: support pulse-per-second output
         - ngbe: add an mdio bus driver
         - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
         - r8152: handle devices with FW with NCM support
         - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
         - virtio-net: support multi buffer XDP
         - virtio/vsock: replace virtio_vsock_pkt with sk_buff
         - tsnep: XDP support

   - Ethernet high-speed switches:
      - nVidia/Mellanox (mlxsw):
         - add support for latency TLV (in FW control messages)
      - Microchip (sparx5):
         - separate explicit and implicit traffic forwarding rules, make
           the implicit rules always active
         - add support for egress DSCP rewrite
         - IS0 VCAP support (Ingress Classification)
         - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
           etc.)
         - ES2 VCAP support (Egress Access Control)
         - support for Per-Stream Filtering and Policing (802.1Q,
           8.6.5.1)

   - Ethernet embedded switches:
      - Marvell (mv88e6xxx):
         - add MAB (port auth) offload support
         - enable PTP receive for mv88e6390
      - NXP (ocelot):
         - support MAC Merge layer
         - support for the the vsc7512 internal copper phys
      - Microchip:
         - lan9303: convert to PHYLINK
         - lan966x: support TC flower filter statistics
         - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
         - lan937x: support Credit Based Shaper configuration
         - ksz9477: support Energy Efficient Ethernet
      - other:
         - qca8k: convert to regmap read/write API, use bulk operations
         - rswitch: Improve TX timestamp accuracy

   - Intel WiFi (iwlwifi):
      - EHT (Wi-Fi 7) rate reporting
      - STEP equalizer support: transfer some STEP (connection to radio
        on platforms with integrated wifi) related parameters from the
        BIOS to the firmware.

   - Qualcomm 802.11ax WiFi (ath11k):
      - IPQ5018 support
      - Fine Timing Measurement (FTM) responder role support
      - channel 177 support

   - MediaTek WiFi (mt76):
      - per-PHY LED support
      - mt7996: EHT (Wi-Fi 7) support
      - Wireless Ethernet Dispatch (WED) reset support
      - switch to using page pool allocator

   - RealTek WiFi (rtw89):
      - support new version of Bluetooth co-existance

   - Mobile:
      - rmnet: support TX aggregation"

* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
  page_pool: add a comment explaining the fragment counter usage
  net: ethtool: fix __ethtool_dev_mm_supported() implementation
  ethtool: pse-pd: Fix double word in comments
  xsk: add linux/vmalloc.h to xsk.c
  sefltests: netdevsim: wait for devlink instance after netns removal
  selftest: fib_tests: Always cleanup before exit
  net/mlx5e: Align IPsec ASO result memory to be as required by hardware
  net/mlx5e: TC, Set CT miss to the specific ct action instance
  net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
  net/mlx5: Refactor tc miss handling to a single function
  net/mlx5: Kconfig: Make tc offload depend on tc skb extension
  net/sched: flower: Support hardware miss to tc action
  net/sched: flower: Move filter handle initialization earlier
  net/sched: cls_api: Support hardware miss to tc action
  net/sched: Rename user cookie and act cookie
  sfc: fix builds without CONFIG_RTC_LIB
  sfc: clean up some inconsistent indentings
  net/mlx4_en: Introduce flexible array to silence overflow warning
  net: lan966x: Fix possible deadlock inside PTP
  net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
  ...

1 files changed, 393 insertions, 0 deletions

diff --git a/Documentation/bpf/cpumasks.rst b/Documentation/bpf/cpumasks.rst
new file mode 100644
index 000000000..24bef9cbb
--- /dev/null
+++ b/Documentation/bpf/cpumasks.rst
@@ -0,0 +1,393 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. _cpumasks-header-label:
+
+==================
+BPF cpumask kfuncs
+==================
+
+1. Introduction
+===============
+
+``struct cpumask`` is a bitmap data structure in the kernel whose indices
+reflect the CPUs on the system. Commonly, cpumasks are used to track which CPUs
+a task is affinitized to, but they can also be used to e.g. track which cores
+are associated with a scheduling domain, which cores on a machine are idle,
+etc.
+
+BPF provides programs with a set of :ref:`kfuncs-header-label` that can be
+used to allocate, mutate, query, and free cpumasks.
+
+2. BPF cpumask objects
+======================
+
+There are two different types of cpumasks that can be used by BPF programs.
+
+2.1 ``struct bpf_cpumask *``
+----------------------------
+
+``struct bpf_cpumask *`` is a cpumask that is allocated by BPF, on behalf of a
+BPF program, and whose lifecycle is entirely controlled by BPF. These cpumasks
+are RCU-protected, can be mutated, can be used as kptrs, and can be safely cast
+to a ``struct cpumask *``.
+
+2.1.1 ``struct bpf_cpumask *`` lifecycle
+----------------------------------------
+
+A ``struct bpf_cpumask *`` is allocated, acquired, and released, using the
+following functions:
+
+.. kernel-doc:: kernel/bpf/cpumask.c
+  :identifiers: bpf_cpumask_create
+
+.. kernel-doc:: kernel/bpf/cpumask.c
+  :identifiers: bpf_cpumask_acquire
+
+.. kernel-doc:: kernel/bpf/cpumask.c
+  :identifiers: bpf_cpumask_release
+
+For example:
+
+.. code-block:: c
+
+        struct cpumask_map_value {
+                struct bpf_cpumask __kptr_ref * cpumask;
+        };
+
+        struct array_map {
+                __uint(type, BPF_MAP_TYPE_ARRAY);
+                __type(key, int);
+                __type(value, struct cpumask_map_value);
+                __uint(max_entries, 65536);
+        } cpumask_map SEC(".maps");
+
+        static int cpumask_map_insert(struct bpf_cpumask *mask, u32 pid)
+        {
+                struct cpumask_map_value local, *v;
+                long status;
+                struct bpf_cpumask *old;
+                u32 key = pid;
+
+                local.cpumask = NULL;
+                status = bpf_map_update_elem(&cpumask_map, &key, &local, 0);
+                if (status) {
+                        bpf_cpumask_release(mask);
+                        return status;
+                }
+
+                v = bpf_map_lookup_elem(&cpumask_map, &key);
+                if (!v) {
+                        bpf_cpumask_release(mask);
+                        return -ENOENT;
+                }
+
+                old = bpf_kptr_xchg(&v->cpumask, mask);
+                if (old)
+                        bpf_cpumask_release(old);
+
+                return 0;
+        }
+
+        /**
+         * A sample tracepoint showing how a task's cpumask can be queried and
+         * recorded as a kptr.
+         */
+        SEC("tp_btf/task_newtask")
+        int BPF_PROG(record_task_cpumask, struct task_struct *task, u64 clone_flags)
+        {
+                struct bpf_cpumask *cpumask;
+                int ret;
+
+                cpumask = bpf_cpumask_create();
+                if (!cpumask)
+                        return -ENOMEM;
+
+                if (!bpf_cpumask_full(task->cpus_ptr))
+                        bpf_printk("task %s has CPU affinity", task->comm);
+
+                bpf_cpumask_copy(cpumask, task->cpus_ptr);
+                return cpumask_map_insert(cpumask, task->pid);
+        }
+
+----
+
+2.1.1 ``struct bpf_cpumask *`` as kptrs
+---------------------------------------
+
+As mentioned and illustrated above, these ``struct bpf_cpumask *`` objects can
+also be stored in a map and used as kptrs. If a ``struct bpf_cpumask *`` is in
+a map, the reference can be removed from the map with bpf_kptr_xchg(), or
+opportunistically acquired with bpf_cpumask_kptr_get():
+
+.. kernel-doc:: kernel/bpf/cpumask.c
+  :identifiers: bpf_cpumask_kptr_get
+
+Here is an example of a ``struct bpf_cpumask *`` being retrieved from a map:
+
+.. code-block:: c
+
+	/* struct containing the struct bpf_cpumask kptr which is stored in the map. */
+	struct cpumasks_kfunc_map_value {
+		struct bpf_cpumask __kptr_ref * bpf_cpumask;
+	};
+
+	/* The map containing struct cpumasks_kfunc_map_value entries. */
+	struct {
+		__uint(type, BPF_MAP_TYPE_ARRAY);
+		__type(key, int);
+		__type(value, struct cpumasks_kfunc_map_value);
+		__uint(max_entries, 1);
+	} cpumasks_kfunc_map SEC(".maps");
+
+	/* ... */
+
+	/**
+	 * A simple example tracepoint program showing how a
+	 * struct bpf_cpumask * kptr that is stored in a map can
+	 * be acquired using the bpf_cpumask_kptr_get() kfunc.
+	 */
+	SEC("tp_btf/cgroup_mkdir")
+	int BPF_PROG(cgrp_ancestor_example, struct cgroup *cgrp, const char *path)
+	{
+		struct bpf_cpumask *kptr;
+		struct cpumasks_kfunc_map_value *v;
+		u32 key = 0;
+
+		/* Assume a bpf_cpumask * kptr was previously stored in the map. */
+		v = bpf_map_lookup_elem(&cpumasks_kfunc_map, &key);
+		if (!v)
+			return -ENOENT;
+
+		/* Acquire a reference to the bpf_cpumask * kptr that's already stored in the map. */
+		kptr = bpf_cpumask_kptr_get(&v->cpumask);
+		if (!kptr)
+			/* If no bpf_cpumask was present in the map, it's because
+			 * we're racing with another CPU that removed it with
+			 * bpf_kptr_xchg() between the bpf_map_lookup_elem()
+			 * above, and our call to bpf_cpumask_kptr_get().
+			 * bpf_cpumask_kptr_get() internally safely handles this
+			 * race, and will return NULL if the cpumask is no longer
+			 * present in the map by the time we invoke the kfunc.
+			 */
+			return -EBUSY;
+
+		/* Free the reference we just took above. Note that the
+		 * original struct bpf_cpumask * kptr is still in the map. It will
+		 * be freed either at a later time if another context deletes
+		 * it from the map, or automatically by the BPF subsystem if
+		 * it's still present when the map is destroyed.
+		 */
+		bpf_cpumask_release(kptr);
+
+		return 0;
+	}
+
+----
+
+2.2 ``struct cpumask``
+----------------------
+
+``struct cpumask`` is the object that actually contains the cpumask bitmap
+being queried, mutated, etc. A ``struct bpf_cpumask`` wraps a ``struct
+cpumask``, which is why it's safe to cast it as such (note however that it is
+**not** safe to cast a ``struct cpumask *`` to a ``struct bpf_cpumask *``, and
+the verifier will reject any program that tries to do so).
+
+As we'll see below, any kfunc that mutates its cpumask argument will take a
+``struct bpf_cpumask *`` as that argument. Any argument that simply queries the
+cpumask will instead take a ``struct cpumask *``.
+
+3. cpumask kfuncs
+=================
+
+Above, we described the kfuncs that can be used to allocate, acquire, release,
+etc a ``struct bpf_cpumask *``. This section of the document will describe the
+kfuncs for mutating and querying cpumasks.
+
+3.1 Mutating cpumasks
+---------------------
+
+Some cpumask kfuncs are "read-only" in that they don't mutate any of their
+arguments, whereas others mutate at least one argument (which means that the
+argument must be a ``struct bpf_cpumask *``, as described above).
+
+This section will describe all of the cpumask kfuncs which mutate at least one
+argument. :ref:`cpumasks-querying-label` below describes the read-only kfuncs.
+
+3.1.1 Setting and clearing CPUs
+-------------------------------
+
+bpf_cpumask_set_cpu() and bpf_cpumask_clear_cpu() can be used to set and clear
+a CPU in a ``struct bpf_cpumask`` respectively:
+
+.. kernel-doc:: kernel/bpf/cpumask.c
+   :identifiers: bpf_cpumask_set_cpu bpf_cpumask_clear_cpu
+
+These kfuncs are pretty straightforward, and can be used, for example, as
+follows:
+
+.. code-block:: c
+
+        /**
+         * A sample tracepoint showing how a cpumask can be queried.
+         */
+        SEC("tp_btf/task_newtask")
+        int BPF_PROG(test_set_clear_cpu, struct task_struct *task, u64 clone_flags)
+        {
+                struct bpf_cpumask *cpumask;
+
+                cpumask = bpf_cpumask_create();
+                if (!cpumask)
+                        return -ENOMEM;
+
+                bpf_cpumask_set_cpu(0, cpumask);
+                if (!bpf_cpumask_test_cpu(0, cast(cpumask)))
+                        /* Should never happen. */
+                        goto release_exit;
+
+                bpf_cpumask_clear_cpu(0, cpumask);
+                if (bpf_cpumask_test_cpu(0, cast(cpumask)))
+                        /* Should never happen. */
+                        goto release_exit;
+
+                /* struct cpumask * pointers such as task->cpus_ptr can also be queried. */
+                if (bpf_cpumask_test_cpu(0, task->cpus_ptr))
+                        bpf_printk("task %s can use CPU %d", task->comm, 0);
+
+        release_exit:
+                bpf_cpumask_release(cpumask);
+                return 0;
+        }
+
+----
+
+bpf_cpumask_test_and_set_cpu() and bpf_cpumask_test_and_clear_cpu() are
+complementary kfuncs that allow callers to atomically test and set (or clear)
+CPUs:
+
+.. kernel-doc:: kernel/bpf/cpumask.c
+   :identifiers: bpf_cpumask_test_and_set_cpu bpf_cpumask_test_and_clear_cpu
+
+----
+
+We can also set and clear entire ``struct bpf_cpumask *`` objects in one
+operation using bpf_cpumask_setall() and bpf_cpumask_clear():
+
+.. kernel-doc:: kernel/bpf/cpumask.c
+   :identifiers: bpf_cpumask_setall bpf_cpumask_clear
+
+3.1.2 Operations between cpumasks
+---------------------------------
+
+In addition to setting and clearing individual CPUs in a single cpumask,
+callers can also perform bitwise operations between multiple cpumasks using
+bpf_cpumask_and(), bpf_cpumask_or(), and bpf_cpumask_xor():
+
+.. kernel-doc:: kernel/bpf/cpumask.c
+   :identifiers: bpf_cpumask_and bpf_cpumask_or bpf_cpumask_xor
+
+The following is an example of how they may be used. Note that some of the
+kfuncs shown in this example will be covered in more detail below.
+
+.. code-block:: c
+
+        /**
+         * A sample tracepoint showing how a cpumask can be mutated using
+           bitwise operators (and queried).
+         */
+        SEC("tp_btf/task_newtask")
+        int BPF_PROG(test_and_or_xor, struct task_struct *task, u64 clone_flags)
+        {
+                struct bpf_cpumask *mask1, *mask2, *dst1, *dst2;
+
+                mask1 = bpf_cpumask_create();
+                if (!mask1)
+                        return -ENOMEM;
+
+                mask2 = bpf_cpumask_create();
+                if (!mask2) {
+                        bpf_cpumask_release(mask1);
+                        return -ENOMEM;
+                }
+
+                // ...Safely create the other two masks... */
+
+                bpf_cpumask_set_cpu(0, mask1);
+                bpf_cpumask_set_cpu(1, mask2);
+                bpf_cpumask_and(dst1, (const struct cpumask *)mask1, (const struct cpumask *)mask2);
+                if (!bpf_cpumask_empty((const struct cpumask *)dst1))
+                        /* Should never happen. */
+                        goto release_exit;
+
+                bpf_cpumask_or(dst1, (const struct cpumask *)mask1, (const struct cpumask *)mask2);
+                if (!bpf_cpumask_test_cpu(0, (const struct cpumask *)dst1))
+                        /* Should never happen. */
+                        goto release_exit;
+
+                if (!bpf_cpumask_test_cpu(1, (const struct cpumask *)dst1))
+                        /* Should never happen. */
+                        goto release_exit;
+
+                bpf_cpumask_xor(dst2, (const struct cpumask *)mask1, (const struct cpumask *)mask2);
+                if (!bpf_cpumask_equal((const struct cpumask *)dst1,
+                                       (const struct cpumask *)dst2))
+                        /* Should never happen. */
+                        goto release_exit;
+
+         release_exit:
+                bpf_cpumask_release(mask1);
+                bpf_cpumask_release(mask2);
+                bpf_cpumask_release(dst1);
+                bpf_cpumask_release(dst2);
+                return 0;
+        }
+
+----
+
+The contents of an entire cpumask may be copied to another using
+bpf_cpumask_copy():
+
+.. kernel-doc:: kernel/bpf/cpumask.c
+   :identifiers: bpf_cpumask_copy
+
+----
+
+.. _cpumasks-querying-label:
+
+3.2 Querying cpumasks
+---------------------
+
+In addition to the above kfuncs, there is also a set of read-only kfuncs that
+can be used to query the contents of cpumasks.
+
+.. kernel-doc:: kernel/bpf/cpumask.c
+   :identifiers: bpf_cpumask_first bpf_cpumask_first_zero bpf_cpumask_test_cpu
+
+.. kernel-doc:: kernel/bpf/cpumask.c
+   :identifiers: bpf_cpumask_equal bpf_cpumask_intersects bpf_cpumask_subset
+                 bpf_cpumask_empty bpf_cpumask_full
+
+.. kernel-doc:: kernel/bpf/cpumask.c
+   :identifiers: bpf_cpumask_any bpf_cpumask_any_and
+
+----
+
+Some example usages of these querying kfuncs were shown above. We will not
+replicate those exmaples here. Note, however, that all of the aforementioned
+kfuncs are tested in `tools/testing/selftests/bpf/progs/cpumask_success.c`_, so
+please take a look there if you're looking for more examples of how they can be
+used.
+
+.. _tools/testing/selftests/bpf/progs/cpumask_success.c:
+   https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/tools/testing/selftests/bpf/progs/cpumask_success.c
+
+
+4. Adding BPF cpumask kfuncs
+============================
+
+The set of supported BPF cpumask kfuncs are not (yet) a 1-1 match with the
+cpumask operations in include/linux/cpumask.h. Any of those cpumask operations
+could easily be encapsulated in a new kfunc if and when required. If you'd like
+to support a new cpumask operation, please feel free to submit a patch. If you
+do add a new cpumask kfunc, please document it here, and add any relevant
+selftest testcases to the cpumask selftest suite.