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, 36 insertions, 0 deletions

diff --git a/include/uapi/fwctl/mlx5.h b/include/uapi/fwctl/mlx5.h
new file mode 100644
index 000000000..625819180
--- /dev/null
+++ b/include/uapi/fwctl/mlx5.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Copyright (c) 2024-2025, NVIDIA CORPORATION & AFFILIATES
+ *
+ * These are definitions for the command interface for mlx5 HW. mlx5 FW has a
+ * User Context mechanism which allows the FW to understand a security scope.
+ * FWCTL binds each FD to a FW user context and then places the User Context ID
+ * (UID) in each command header. The created User Context has a capability set
+ * that is appropriate for FWCTL's security model.
+ *
+ * Command formation should use a copy of the structs in mlx5_ifc.h following
+ * the Programmers Reference Manual. A open release is available here:
+ *
+ *  https://network.nvidia.com/files/doc-2020/ethernet-adapters-programming-manual.pdf
+ *
+ * The device_type for this file is FWCTL_DEVICE_TYPE_MLX5.
+ */
+#ifndef _UAPI_FWCTL_MLX5_H
+#define _UAPI_FWCTL_MLX5_H
+
+#include <linux/types.h>
+
+/**
+ * struct fwctl_info_mlx5 - ioctl(FWCTL_INFO) out_device_data
+ * @uid: The FW UID this FD is bound to. Each command header will force
+ *	this value.
+ * @uctx_caps: The FW capabilities that are enabled for the uid.
+ *
+ * Return basic information about the FW interface available.
+ */
+struct fwctl_info_mlx5 {
+	__u32 uid;
+	__u32 uctx_caps;
+};
+
+#endif