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, 84 insertions, 0 deletions

diff --git a/tools/perf/util/namespaces.h b/tools/perf/util/namespaces.h
new file mode 100644
index 000000000..e95c79b80
--- /dev/null
+++ b/tools/perf/util/namespaces.h
@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *
+ * Copyright (C) 2017 Hari Bathini, IBM Corporation
+ */
+
+#ifndef __PERF_NAMESPACES_H
+#define __PERF_NAMESPACES_H
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <linux/stddef.h>
+#include <linux/perf_event.h>
+#include <linux/refcount.h>
+#include <linux/types.h>
+#include <internal/rc_check.h>
+
+#ifndef HAVE_SETNS_SUPPORT
+int setns(int fd, int nstype);
+#endif
+
+struct perf_record_namespaces;
+
+struct namespaces {
+	struct list_head list;
+	u64 end_time;
+	struct perf_ns_link_info link_info[];
+};
+
+struct namespaces *namespaces__new(struct perf_record_namespaces *event);
+void namespaces__free(struct namespaces *namespaces);
+
+DECLARE_RC_STRUCT(nsinfo) {
+	pid_t			pid;
+	pid_t			tgid;
+	pid_t			nstgid;
+	bool			need_setns;
+	bool			in_pidns;
+	char			*mntns_path;
+	refcount_t		refcnt;
+};
+
+struct nscookie {
+	int			oldns;
+	int			newns;
+	char			*oldcwd;
+};
+
+int nsinfo__init(struct nsinfo *nsi);
+struct nsinfo *nsinfo__new(pid_t pid);
+struct nsinfo *nsinfo__copy(const struct nsinfo *nsi);
+
+struct nsinfo *nsinfo__get(struct nsinfo *nsi);
+void nsinfo__put(struct nsinfo *nsi);
+
+bool nsinfo__need_setns(const struct nsinfo *nsi);
+void nsinfo__clear_need_setns(struct nsinfo *nsi);
+pid_t nsinfo__tgid(const struct nsinfo  *nsi);
+pid_t nsinfo__nstgid(const struct nsinfo  *nsi);
+pid_t nsinfo__pid(const struct nsinfo  *nsi);
+bool nsinfo__in_pidns(const struct nsinfo  *nsi);
+void nsinfo__set_in_pidns(struct nsinfo *nsi);
+
+void nsinfo__mountns_enter(struct nsinfo *nsi, struct nscookie *nc);
+void nsinfo__mountns_exit(struct nscookie *nc);
+
+char *nsinfo__realpath(const char *path, struct nsinfo *nsi);
+int nsinfo__stat(const char *filename, struct stat *st, struct nsinfo *nsi);
+
+bool nsinfo__is_in_root_namespace(void);
+
+static inline void __nsinfo__zput(struct nsinfo **nsip)
+{
+	if (nsip) {
+		nsinfo__put(*nsip);
+		*nsip = NULL;
+	}
+}
+
+#define nsinfo__zput(nsi) __nsinfo__zput(&nsi)
+
+const char *perf_ns__name(unsigned int id);
+
+#endif  /* __PERF_NAMESPACES_H */