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, 44 insertions, 0 deletions

diff --git a/arch/x86/boot/bitops.h b/arch/x86/boot/bitops.h
new file mode 100644
index 000000000..79e159715
--- /dev/null
+++ b/arch/x86/boot/bitops.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright (C) 1991, 1992 Linus Torvalds
+ *   Copyright 2007 rPath, Inc. - All Rights Reserved
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * Very simple bitops for the boot code.
+ */
+
+#ifndef BOOT_BITOPS_H
+#define BOOT_BITOPS_H
+#define _LINUX_BITOPS_H		/* Inhibit inclusion of <linux/bitops.h> */
+
+#include <linux/types.h>
+#include <asm/asm.h>
+
+static inline bool constant_test_bit(int nr, const void *addr)
+{
+	const u32 *p = addr;
+	return ((1UL << (nr & 31)) & (p[nr >> 5])) != 0;
+}
+static inline bool variable_test_bit(int nr, const void *addr)
+{
+	bool v;
+	const u32 *p = addr;
+
+	asm("btl %2,%1" : "=@ccc" (v) : "m" (*p), "Ir" (nr));
+	return v;
+}
+
+#define test_bit(nr,addr) \
+(__builtin_constant_p(nr) ? \
+ constant_test_bit((nr),(addr)) : \
+ variable_test_bit((nr),(addr)))
+
+static inline void set_bit(int nr, void *addr)
+{
+	asm("btsl %1,%0" : "+m" (*(u32 *)addr) : "Ir" (nr));
+}
+
+#endif /* BOOT_BITOPS_H */