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, 18 insertions, 0 deletions

diff --git a/include/acpi/nfit.h b/include/acpi/nfit.h
new file mode 100644
index 000000000..86ed07c12
--- /dev/null
+++ b/include/acpi/nfit.h
@@ -0,0 +1,18 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0
+ * Copyright (C) 2018 Intel Corporation
+ */
+
+#ifndef __ACPI_NFIT_H
+#define __ACPI_NFIT_H
+
+#if IS_ENABLED(CONFIG_ACPI_NFIT)
+int nfit_get_smbios_id(u32 device_handle, u16 *flags);
+#else
+static inline int nfit_get_smbios_id(u32 device_handle, u16 *flags)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
+#endif /* __ACPI_NFIT_H */