x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 82 insertions, 0 deletions

diff --git a/Documentation/bpf/maps.rst b/Documentation/bpf/maps.rst
new file mode 100644
index 000000000..6f069f3d6
--- /dev/null
+++ b/Documentation/bpf/maps.rst
@@ -0,0 +1,82 @@
+
+========
+BPF maps
+========
+
+BPF 'maps' provide generic storage of different types for sharing data between
+kernel and user space. There are several storage types available, including
+hash, array, bloom filter and radix-tree. Several of the map types exist to
+support specific BPF helpers that perform actions based on the map contents. The
+maps are accessed from BPF programs via BPF helpers which are documented in the
+`man-pages`_ for `bpf-helpers(7)`_.
+
+BPF maps are accessed from user space via the ``bpf`` syscall, which provides
+commands to create maps, lookup elements, update elements and delete elements.
+More details of the BPF syscall are available in `ebpf-syscall`_ and in the
+`man-pages`_ for `bpf(2)`_.
+
+Map Types
+=========
+
+.. toctree::
+   :maxdepth: 1
+   :glob:
+
+   map_*
+
+Usage Notes
+===========
+
+.. c:function::
+   int bpf(int command, union bpf_attr *attr, u32 size)
+
+Use the ``bpf()`` system call to perform the operation specified by
+``command``. The operation takes parameters provided in ``attr``. The ``size``
+argument is the size of the ``union bpf_attr`` in ``attr``.
+
+**BPF_MAP_CREATE**
+
+Create a map with the desired type and attributes in ``attr``:
+
+.. code-block:: c
+
+    int fd;
+    union bpf_attr attr = {
+            .map_type = BPF_MAP_TYPE_ARRAY;  /* mandatory */
+            .key_size = sizeof(__u32);       /* mandatory */
+            .value_size = sizeof(__u32);     /* mandatory */
+            .max_entries = 256;              /* mandatory */
+            .map_flags = BPF_F_MMAPABLE;
+            .map_name = "example_array";
+    };
+
+    fd = bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+
+Returns a process-local file descriptor on success, or negative error in case of
+failure. The map can be deleted by calling ``close(fd)``. Maps held by open
+file descriptors will be deleted automatically when a process exits.
+
+.. note:: Valid characters for ``map_name`` are ``A-Z``, ``a-z``, ``0-9``,
+   ``'_'`` and ``'.'``.
+
+**BPF_MAP_LOOKUP_ELEM**
+
+Lookup key in a given map using ``attr->map_fd``, ``attr->key``,
+``attr->value``. Returns zero and stores found elem into ``attr->value`` on
+success, or negative error on failure.
+
+**BPF_MAP_UPDATE_ELEM**
+
+Create or update key/value pair in a given map using ``attr->map_fd``, ``attr->key``,
+``attr->value``. Returns zero on success or negative error on failure.
+
+**BPF_MAP_DELETE_ELEM**
+
+Find and delete element by key in a given map using ``attr->map_fd``,
+``attr->key``. Returns zero on success or negative error on failure.
+
+.. Links:
+.. _man-pages: https://www.kernel.org/doc/man-pages/
+.. _bpf(2): https://man7.org/linux/man-pages/man2/bpf.2.html
+.. _bpf-helpers(7): https://man7.org/linux/man-pages/man7/bpf-helpers.7.html
+.. _ebpf-syscall: https://docs.kernel.org/userspace-api/ebpf/syscall.html