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, 53 insertions, 0 deletions

diff --git a/rust/helpers/spinlock.c b/rust/helpers/spinlock.c
new file mode 100644
index 000000000..d53400c15
--- /dev/null
+++ b/rust/helpers/spinlock.c
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/spinlock.h>
+
+__rust_helper void rust_helper___spin_lock_init(spinlock_t *lock,
+						const char *name,
+						struct lock_class_key *key)
+{
+#ifdef CONFIG_DEBUG_SPINLOCK
+# if defined(CONFIG_PREEMPT_RT)
+	__spin_lock_init(lock, name, key, false);
+# else /*!CONFIG_PREEMPT_RT */
+	__raw_spin_lock_init(spinlock_check(lock), name, key, LD_WAIT_CONFIG);
+# endif /* CONFIG_PREEMPT_RT */
+#else /* !CONFIG_DEBUG_SPINLOCK */
+	spin_lock_init(lock);
+#endif /* CONFIG_DEBUG_SPINLOCK */
+}
+
+__rust_helper void rust_helper_spin_lock(spinlock_t *lock)
+{
+	spin_lock(lock);
+}
+
+__rust_helper void rust_helper_spin_unlock(spinlock_t *lock)
+{
+	spin_unlock(lock);
+}
+
+__rust_helper int rust_helper_spin_trylock(spinlock_t *lock)
+{
+	return spin_trylock(lock);
+}
+
+__rust_helper void rust_helper_spin_assert_is_held(spinlock_t *lock)
+{
+	lockdep_assert_held(lock);
+}
+
+__rust_helper void rust_helper_spin_lock_irq_disable(spinlock_t *lock)
+{
+	spin_lock_irq_disable(lock);
+}
+
+__rust_helper void rust_helper_spin_unlock_irq_enable(spinlock_t *lock)
+{
+	spin_unlock_irq_enable(lock);
+}
+
+__rust_helper int rust_helper_spin_trylock_irq_disable(spinlock_t *lock)
+{
+	return spin_trylock_irq_disable(lock);
+}