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, 27 insertions, 0 deletions

diff --git a/tools/perf/util/btf.c b/tools/perf/util/btf.c
new file mode 100644
index 000000000..50d98f3e8
--- /dev/null
+++ b/tools/perf/util/btf.c
@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Arnaldo Carvalho de Melo <acme@redhat.com>
+ *
+ * Copyright (C) 2024, Red Hat, Inc
+ */
+
+#include <bpf/btf.h>
+#include <util/btf.h>
+#include <string.h>
+
+const struct btf_member *__btf_type__find_member_by_name(struct btf *btf,
+							 int type_id, const char *member_name)
+{
+	const struct btf_type *t = btf__type_by_id(btf, type_id);
+	const struct btf_member *m;
+	u32 i;
+
+	for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
+		const char *current_member_name = btf__name_by_offset(btf, m->name_off);
+
+		if (!strcmp(current_member_name, member_name))
+			return m;
+	}
+
+	return NULL;
+}