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, 29 insertions, 0 deletions

diff --git a/lib/iommu-helper.c b/lib/iommu-helper.c
new file mode 100644
index 000000000..92a9f243c
--- /dev/null
+++ b/lib/iommu-helper.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * IOMMU helper functions for the free area management
+ */
+
+#include <linux/bitmap.h>
+#include <linux/iommu-helper.h>
+
+unsigned long iommu_area_alloc(unsigned long *map, unsigned long size,
+			       unsigned long start, unsigned int nr,
+			       unsigned long shift, unsigned long boundary_size,
+			       unsigned long align_mask)
+{
+	unsigned long index;
+
+	/* We don't want the last of the limit */
+	size -= 1;
+again:
+	index = bitmap_find_next_zero_area(map, size, start, nr, align_mask);
+	if (index < size) {
+		if (iommu_is_span_boundary(index, nr, shift, boundary_size)) {
+			start = ALIGN(shift + index, boundary_size) - shift;
+			goto again;
+		}
+		bitmap_set(map, index, nr);
+		return index;
+	}
+	return -1;
+}