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, 127 insertions, 0 deletions

diff --git a/tools/perf/util/trace-event.c b/tools/perf/util/trace-event.c
new file mode 100644
index 000000000..000c1e1d6
--- /dev/null
+++ b/tools/perf/util/trace-event.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <event-parse.h>
+#include <api/fs/tracing_path.h>
+#include <api/fs/fs.h>
+#include "trace-event.h"
+#include "machine.h"
+
+/*
+ * global trace_event object used by trace_event__tp_format
+ *
+ * TODO There's no cleanup call for this. Add some sort of
+ * __exit function support and call trace_event__cleanup
+ * there.
+ */
+static struct trace_event tevent;
+static bool tevent_initialized;
+
+int trace_event__init(struct trace_event *t)
+{
+	struct tep_handle *pevent;
+
+	trace_event__cleanup(t);
+
+	pevent = tep_alloc();
+
+	if (pevent) {
+		t->plugin_list = tep_load_plugins(pevent);
+		t->pevent  = pevent;
+	}
+
+	return pevent ? 0 : -1;
+}
+
+static int trace_event__init2(void)
+{
+	int be = tep_is_bigendian();
+	struct tep_handle *pevent;
+
+	if (trace_event__init(&tevent))
+		return -1;
+
+	pevent = tevent.pevent;
+	tep_set_flag(pevent, TEP_NSEC_OUTPUT);
+	tep_set_file_bigendian(pevent, be);
+	tep_set_local_bigendian(pevent, be);
+	tevent_initialized = true;
+	return 0;
+}
+
+int trace_event__register_resolver(struct machine *machine,
+				   tep_func_resolver_t *func)
+{
+	if (!tevent_initialized && trace_event__init2())
+		return -1;
+
+	return tep_set_function_resolver(tevent.pevent, func, machine);
+}
+
+void trace_event__cleanup(struct trace_event *t)
+{
+	if (!t->pevent)
+		return;
+
+	tep_unload_plugins(t->plugin_list, t->pevent);
+	tep_free(t->pevent);
+	t->pevent = NULL;
+	t->plugin_list = NULL;
+}
+
+/*
+ * Returns pointer with encoded error via <linux/err.h> interface.
+ */
+static struct tep_event*
+tp_format(const char *sys, const char *name)
+{
+	char *tp_dir = get_events_file(sys);
+	struct tep_handle *pevent = tevent.pevent;
+	struct tep_event *event = NULL;
+	char path[PATH_MAX];
+	size_t size;
+	char *data;
+	int err;
+
+	if (!tp_dir)
+		return ERR_PTR(-errno);
+
+	scnprintf(path, PATH_MAX, "%s/%s/format", tp_dir, name);
+	put_events_file(tp_dir);
+
+	err = filename__read_str(path, &data, &size);
+	if (err)
+		return ERR_PTR(err);
+
+	tep_parse_format(pevent, &event, data, size, sys);
+
+	free(data);
+	return event;
+}
+
+/*
+ * Returns pointer with encoded error via <linux/err.h> interface.
+ */
+struct tep_event*
+trace_event__tp_format(const char *sys, const char *name)
+{
+	if (!tevent_initialized && trace_event__init2())
+		return ERR_PTR(-ENOMEM);
+
+	return tp_format(sys, name);
+}
+
+struct tep_event *trace_event__tp_format_id(int id)
+{
+	if (!tevent_initialized && trace_event__init2())
+		return ERR_PTR(-ENOMEM);
+
+	return tep_find_event(tevent.pevent, id);
+}