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, 78 insertions, 0 deletions

diff --git a/rust/helpers/drm.c b/rust/helpers/drm.c
new file mode 100644
index 000000000..65f3f22b0
--- /dev/null
+++ b/rust/helpers/drm.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <drm/drm_gem.h>
+#include <drm/drm_gem_shmem_helper.h>
+#include <drm/drm_vma_manager.h>
+
+#ifdef CONFIG_DRM
+
+__rust_helper void rust_helper_drm_gem_object_get(struct drm_gem_object *obj)
+{
+	drm_gem_object_get(obj);
+}
+
+__rust_helper void rust_helper_drm_gem_object_put(struct drm_gem_object *obj)
+{
+	drm_gem_object_put(obj);
+}
+
+__rust_helper __u64
+rust_helper_drm_vma_node_offset_addr(struct drm_vma_offset_node *node)
+{
+	return drm_vma_node_offset_addr(node);
+}
+
+#ifdef CONFIG_DRM_GEM_SHMEM_HELPER
+__rust_helper void
+rust_helper_drm_gem_shmem_object_free(struct drm_gem_object *obj)
+{
+	return drm_gem_shmem_object_free(obj);
+}
+
+__rust_helper void
+rust_helper_drm_gem_shmem_object_print_info(struct drm_printer *p, unsigned int indent,
+					    const struct drm_gem_object *obj)
+{
+	drm_gem_shmem_object_print_info(p, indent, obj);
+}
+
+__rust_helper int
+rust_helper_drm_gem_shmem_object_pin(struct drm_gem_object *obj)
+{
+	return drm_gem_shmem_object_pin(obj);
+}
+
+__rust_helper void
+rust_helper_drm_gem_shmem_object_unpin(struct drm_gem_object *obj)
+{
+	drm_gem_shmem_object_unpin(obj);
+}
+
+__rust_helper struct sg_table *
+rust_helper_drm_gem_shmem_object_get_sg_table(struct drm_gem_object *obj)
+{
+	return drm_gem_shmem_object_get_sg_table(obj);
+}
+
+__rust_helper int
+rust_helper_drm_gem_shmem_object_vmap(struct drm_gem_object *obj,
+				      struct iosys_map *map)
+{
+	return drm_gem_shmem_object_vmap(obj, map);
+}
+
+__rust_helper void
+rust_helper_drm_gem_shmem_object_vunmap(struct drm_gem_object *obj,
+					struct iosys_map *map)
+{
+	drm_gem_shmem_object_vunmap(obj, map);
+}
+
+__rust_helper int
+rust_helper_drm_gem_shmem_object_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
+{
+	return drm_gem_shmem_object_mmap(obj, vma);
+}
+
+#endif /* CONFIG_DRM_GEM_SHMEM_HELPER */
+#endif /* CONFIG_DRM */