Hi Maryam, On Thu, 17 Nov 2022 10:44:46 -0500, mtahhan@xxxxxxxxxx wrote: > From: Maryam Tahhan <mtahhan@xxxxxxxxxx> > > Add documentation for BPF_MAP_TYPE_XSKMAP > including kernel version introduced, usage > and examples. > > Signed-off-by: Maryam Tahhan <mtahhan@xxxxxxxxxx> > > --- > v2: > - Fixed typos + incorrect return type references. > - Adjusted examples to use __u32 and fixed references to key_size. > - Changed `AF_XDP socket` references to XSK. > - Added note re map key and value size. > --- > Documentation/bpf/map_xskmap.rst | 167 +++++++++++++++++++++++++++++++ > 1 file changed, 167 insertions(+) > create mode 100644 Documentation/bpf/map_xskmap.rst > > diff --git a/Documentation/bpf/map_xskmap.rst b/Documentation/bpf/map_xskmap.rst > new file mode 100644 [...] > +Kernel BPF > +---------- > +.. c:function:: > + long bpf_redirect_map(struct bpf_map *map, u32 key, u64 flags) > + > + Redirect the packet to the endpoint referenced by ``map`` at index ``key``. > + For ``BPF_MAP_TYPE_XSKMAP`` this map contains references to XSK FDs > + for sockets attached to a netdev's queues. > + > + .. note:: > + If the map is empty at an index, the packet is dropped. This means that it is > + necessary to have an XDP program loaded with at least one XSK in the > + XSKMAP to be able to get any traffic to user space through the socket. > + > +.. c:function:: > + void *bpf_map_lookup_elem(struct bpf_map *map, const void *key) > + > + XSK entry references of type ``struct xdp_sock *`` can be retrieved using the > + ``bpf_map_lookup_elem()`` helper. > + > +Userspace > +--------- > +.. note:: > + XSK entries can only be updated/deleted from user space and not from > + an eBPF program. Trying to call these functions from a kernel eBPF program will > + result in the program failing to load and a verifier warning. > + > +.. c:function:: > + int bpf_map_update_elem(int fd, const void *key, const void *value, __u64 flags) > + > + XSK entries can be added or updated using the ``bpf_map_update_elem()`` > + helper. The ``key`` parameter is equal to the queue_id of the queue the XSK > + is attaching to. And the ``value`` parameter is the FD value of that socket. > + > + Under the hood, the XSKMAP update function uses the XSK FD value to retrieve the > + associated ``struct xdp_sock`` instance. > + > + The flags argument can be one of the following: > + > + - BPF_ANY: Create a new element or update an existing element. > + - BPF_NOEXIST: Create a new element only if it did not exist. > + - BPF_EXIST: Update an existing element. > + > +.. c:function:: > + int bpf_map_lookup_elem(int fd, const void *key, void *value) > + So you have two declarations of bpf_map_lookup_elem() in map_xskmap.rst. This will cause "make htmldocs" with Sphinx >=3.1 to emit a warning of: /linux/Documentation/bpf/map_xskmap.rst:100: WARNING: Duplicate C declaration, also defined at map_xskmap:71. Declaration is '.. c:function:: int bpf_map_lookup_elem(int fd, const void *key, void *value)'. , in addition to a bunch of similar warnings observed at bpf-next: /linux/Documentation/bpf/map_cpumap.rst:50: WARNING: Duplicate C declaration, also defined at map_array:43. Declaration is '.. c:function:: int bpf_map_update_elem(int fd, const void *key, const void *value, __u64 flags);'. /linux/Documentation/bpf/map_cpumap.rst:72: WARNING: Duplicate C declaration, also defined at map_array:35. Declaration is '.. c:function:: int bpf_map_lookup_elem(int fd, const void *key, void *value);'. /linux/Documentation/bpf/map_hash.rst:37: WARNING: Duplicate C declaration, also defined at map_array:43. Declaration is '.. c:function:: long bpf_map_update_elem(struct bpf_map *map, const void *key, const void *value, u64 flags)'. ... [bunch of similar warnings] You might want to say you don't care, but they would annoy those who do test "make htmldocs". So let me explain why sphinx complains. C domain declarations in kernel documentation are for kernel APIs. By default, c:function declarations belong to the top-level namespace, which is intended for kernel APIs. IIUC, most APIs described in map*.rst files don't belong to kernel. So I think the way to go is to use the c:namespace directive. See: https://www.sphinx-doc.org/en/master/usage/restructuredtext/domains.html#namespacing As mentioned there, namespacing works with Sphinx >=3.1. Currently, kernel documentation build scripts support only the "c:namespace" directive, which means you can't switch namespaces in the middle of a .rst file. This limitation comes from the fact that Sphinx 1.7.9 is still in the list for htmldocs at the moment and build scripts emulate namespacing for Sphinx <3.1 in a limited way. So please avoid putting function declarations of the same name in a .rst file. The other duplicate warnings shown above can be silenced by the change attached below. It is only as a suggestion and I'm not putting a S-o-b tag. Hope this helps, Akira -------- diff --git a/Documentation/bpf/map_array.rst b/Documentation/bpf/map_array.rst index 97bb80333254..68545702ca78 100644 --- a/Documentation/bpf/map_array.rst +++ b/Documentation/bpf/map_array.rst @@ -1,6 +1,8 @@ .. SPDX-License-Identifier: GPL-2.0-only .. Copyright (C) 2022 Red Hat, Inc. +.. c:namespace:: BPF.MAP_ARRAY + ================================================ BPF_MAP_TYPE_ARRAY and BPF_MAP_TYPE_PERCPU_ARRAY ================================================ diff --git a/Documentation/bpf/map_cpumap.rst b/Documentation/bpf/map_cpumap.rst index 61a797a86342..25e05d14ec82 100644 --- a/Documentation/bpf/map_cpumap.rst +++ b/Documentation/bpf/map_cpumap.rst @@ -1,6 +1,8 @@ .. SPDX-License-Identifier: GPL-2.0-only .. Copyright (C) 2022 Red Hat, Inc. +.. c:namespace:: BPF.MAP_CPUMAP + =================== BPF_MAP_TYPE_CPUMAP =================== diff --git a/Documentation/bpf/map_hash.rst b/Documentation/bpf/map_hash.rst index e85120878b27..3ac93ccf2b0e 100644 --- a/Documentation/bpf/map_hash.rst +++ b/Documentation/bpf/map_hash.rst @@ -1,6 +1,8 @@ .. SPDX-License-Identifier: GPL-2.0-only .. Copyright (C) 2022 Red Hat, Inc. +.. c:namespace:: BPF.MAP_HASH + =============================================== BPF_MAP_TYPE_HASH, with PERCPU and LRU Variants =============================================== diff --git a/Documentation/bpf/map_lpm_trie.rst b/Documentation/bpf/map_lpm_trie.rst index 31be1aa7ba2c..c934c3e2bcb7 100644 --- a/Documentation/bpf/map_lpm_trie.rst +++ b/Documentation/bpf/map_lpm_trie.rst @@ -1,6 +1,8 @@ .. SPDX-License-Identifier: GPL-2.0-only .. Copyright (C) 2022 Red Hat, Inc. +.. c:namespace:: BPF.MAP_LPM_TRIE + ===================== BPF_MAP_TYPE_LPM_TRIE ===================== diff --git a/Documentation/bpf/map_of_maps.rst b/Documentation/bpf/map_of_maps.rst index 07212b9227a9..f59cd0e3a72c 100644 --- a/Documentation/bpf/map_of_maps.rst +++ b/Documentation/bpf/map_of_maps.rst @@ -1,6 +1,8 @@ .. SPDX-License-Identifier: GPL-2.0-only .. Copyright (C) 2022 Red Hat, Inc. +.. c:namespace:: BPF.MAP_OF_MAPS + ======================================================== BPF_MAP_TYPE_ARRAY_OF_MAPS and BPF_MAP_TYPE_HASH_OF_MAPS ======================================================== diff --git a/Documentation/bpf/map_queue_stack.rst b/Documentation/bpf/map_queue_stack.rst index f20e31a647b9..abc8ed569900 100644 --- a/Documentation/bpf/map_queue_stack.rst +++ b/Documentation/bpf/map_queue_stack.rst @@ -1,6 +1,8 @@ .. SPDX-License-Identifier: GPL-2.0-only .. Copyright (C) 2022 Red Hat, Inc. +.. c:namespace:: BPF.MAP_QUEUE_STACK + ========================================= BPF_MAP_TYPE_QUEUE and BPF_MAP_TYPE_STACK ========================================= --
