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, 98 insertions, 0 deletions

diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
new file mode 100644
index 000000000..2945aa7fe
--- /dev/null
+++ b/include/trace/events/skb.h
@@ -0,0 +1,98 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM skb
+
+#if !defined(_TRACE_SKB_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_SKB_H
+
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <linux/tracepoint.h>
+
+#undef FN
+#define FN(reason)	TRACE_DEFINE_ENUM(SKB_DROP_REASON_##reason);
+DEFINE_DROP_REASON(FN, FN)
+
+#undef FN
+#undef FNe
+#define FN(reason)	{ SKB_DROP_REASON_##reason, #reason },
+#define FNe(reason)	{ SKB_DROP_REASON_##reason, #reason }
+
+/*
+ * Tracepoint for free an sk_buff:
+ */
+TRACE_EVENT(kfree_skb,
+
+	TP_PROTO(struct sk_buff *skb, void *location,
+		 enum skb_drop_reason reason, const struct sock *rx_sk),
+
+	TP_ARGS(skb, location, reason, rx_sk),
+
+	TP_STRUCT__entry(
+		__field(void *,		skbaddr)
+		__field(void *,		location)
+		__field(const void *,	rx_sk)
+		__field(unsigned short,	protocol)
+		__field(enum skb_drop_reason,	reason)
+	),
+
+	TP_fast_assign(
+		__entry->skbaddr = skb;
+		__entry->location = location;
+		__entry->rx_sk = rx_sk;
+		__entry->protocol = ntohs(skb->protocol);
+		__entry->reason = reason;
+	),
+
+	TP_printk("skbaddr=%p rx_sk=%p protocol=%u location=%pS reason: %s",
+		  __entry->skbaddr, __entry->rx_sk, __entry->protocol,
+		  __entry->location,
+		  __print_symbolic(__entry->reason,
+				   DEFINE_DROP_REASON(FN, FNe)))
+);
+
+#undef FN
+#undef FNe
+
+TRACE_EVENT(consume_skb,
+
+	TP_PROTO(struct sk_buff *skb, void *location),
+
+	TP_ARGS(skb, location),
+
+	TP_STRUCT__entry(
+		__field(	void *,	skbaddr)
+		__field(	void *,	location)
+	),
+
+	TP_fast_assign(
+		__entry->skbaddr = skb;
+		__entry->location = location;
+	),
+
+	TP_printk("skbaddr=%p location=%pS", __entry->skbaddr, __entry->location)
+);
+
+TRACE_EVENT(skb_copy_datagram_iovec,
+
+	TP_PROTO(const struct sk_buff *skb, int len),
+
+	TP_ARGS(skb, len),
+
+	TP_STRUCT__entry(
+		__field(	const void *,		skbaddr		)
+		__field(	int,			len		)
+	),
+
+	TP_fast_assign(
+		__entry->skbaddr = skb;
+		__entry->len = len;
+	),
+
+	TP_printk("skbaddr=%p len=%d", __entry->skbaddr, __entry->len)
+);
+
+#endif /* _TRACE_SKB_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>