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, 41 insertions, 0 deletions

diff --git a/Documentation/arch/powerpc/elfnote.rst b/Documentation/arch/powerpc/elfnote.rst
new file mode 100644
index 000000000..3ec8d61e9
--- /dev/null
+++ b/Documentation/arch/powerpc/elfnote.rst
@@ -0,0 +1,41 @@
+==========================
+ELF Note PowerPC Namespace
+==========================
+
+The PowerPC namespace in an ELF Note of the kernel binary is used to store
+capabilities and information which can be used by a bootloader or userland.
+
+Types and Descriptors
+---------------------
+
+The types to be used with the "PowerPC" namespace are defined in [#f1]_.
+
+	1) PPC_ELFNOTE_CAPABILITIES
+
+Define the capabilities supported/required by the kernel. This type uses a
+bitmap as "descriptor" field. Each bit is described below:
+
+- Ultravisor-capable bit (PowerNV only).
+
+.. code-block:: c
+
+	#define PPCCAP_ULTRAVISOR_BIT (1 << 0)
+
+Indicate that the powerpc kernel binary knows how to run in an
+ultravisor-enabled system.
+
+In an ultravisor-enabled system, some machine resources are now controlled
+by the ultravisor. If the kernel is not ultravisor-capable, but it ends up
+being run on a machine with ultravisor, the kernel will probably crash
+trying to access ultravisor resources. For instance, it may crash in early
+boot trying to set the partition table entry 0.
+
+In an ultravisor-enabled system, a bootloader could warn the user or prevent
+the kernel from being run if the PowerPC ultravisor capability doesn't exist
+or the Ultravisor-capable bit is not set.
+
+References
+----------
+
+.. [#f1] arch/powerpc/include/asm/elfnote.h
+