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, 19 insertions, 0 deletions

diff --git a/lib/memregion.c b/lib/memregion.c
new file mode 100644
index 000000000..be5cfa5a3
--- /dev/null
+++ b/lib/memregion.c
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* identifiers for device / performance-differentiated memory regions */
+#include <linux/idr.h>
+#include <linux/types.h>
+#include <linux/memregion.h>
+
+static DEFINE_IDA(memregion_ids);
+
+int memregion_alloc(gfp_t gfp)
+{
+	return ida_alloc(&memregion_ids, gfp);
+}
+EXPORT_SYMBOL(memregion_alloc);
+
+void memregion_free(int id)
+{
+	ida_free(&memregion_ids, id);
+}
+EXPORT_SYMBOL(memregion_free);