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, 25 insertions, 0 deletions

diff --git a/rust/macros/export.rs b/rust/macros/export.rs
new file mode 100644
index 000000000..6d53521f6
--- /dev/null
+++ b/rust/macros/export.rs
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use proc_macro2::TokenStream;
+use quote::quote;
+
+/// Please see [`crate::export`] for documentation.
+pub(crate) fn export(f: syn::ItemFn) -> TokenStream {
+    let name = &f.sig.ident;
+
+    quote! {
+        // This verifies that the function has the same signature as the declaration generated by
+        // bindgen. It makes use of the fact that all branches of an if/else must have the same
+        // type.
+        const _: () = {
+            if true {
+                ::kernel::bindings::#name
+            } else {
+                #name
+            };
+        };
+
+        #[no_mangle]
+        #f
+    }
+}