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, 56 insertions, 0 deletions

diff --git a/include/uapi/fwctl/cxl.h b/include/uapi/fwctl/cxl.h
new file mode 100644
index 000000000..43f522f0c
--- /dev/null
+++ b/include/uapi/fwctl/cxl.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Copyright (c) 2024-2025 Intel Corporation
+ *
+ * These are definitions for the mailbox command interface of CXL subsystem.
+ */
+#ifndef _UAPI_FWCTL_CXL_H_
+#define _UAPI_FWCTL_CXL_H_
+
+#include <linux/types.h>
+#include <linux/stddef.h>
+#include <cxl/features.h>
+
+/**
+ * struct fwctl_rpc_cxl - ioctl(FWCTL_RPC) input for CXL
+ * @opcode: CXL mailbox command opcode
+ * @flags: Flags for the command (input).
+ * @op_size: Size of input payload.
+ * @reserved1: Reserved. Must be 0s.
+ * @get_sup_feats_in: Get Supported Features input
+ * @get_feat_in: Get Feature input
+ * @set_feat_in: Set Feature input
+ */
+struct fwctl_rpc_cxl {
+	__struct_group(fwctl_rpc_cxl_hdr, hdr, /* no attrs */,
+		__u32 opcode;
+		__u32 flags;
+		__u32 op_size;
+		__u32 reserved1;
+	);
+	union {
+		struct cxl_mbox_get_sup_feats_in get_sup_feats_in;
+		struct cxl_mbox_get_feat_in get_feat_in;
+		struct cxl_mbox_set_feat_in set_feat_in;
+	};
+};
+
+/**
+ * struct fwctl_rpc_cxl_out - ioctl(FWCTL_RPC) output for CXL
+ * @size: Size of the output payload
+ * @retval: Return value from device
+ * @get_sup_feats_out: Get Supported Features output
+ * @payload: raw byte stream of payload
+ */
+struct fwctl_rpc_cxl_out {
+	__struct_group(fwctl_rpc_cxl_out_hdr, hdr, /* no attrs */,
+		__u32 size;
+		__u32 retval;
+	);
+	union {
+		struct cxl_mbox_get_sup_feats_out get_sup_feats_out;
+		__DECLARE_FLEX_ARRAY(__u8, payload);
+	};
+};
+
+#endif