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, 117 insertions, 0 deletions

diff --git a/drivers/virtio/virtio_debug.c b/drivers/virtio/virtio_debug.c
new file mode 100644
index 000000000..ccf1955a1
--- /dev/null
+++ b/drivers/virtio/virtio_debug.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/debugfs.h>
+
+static struct dentry *virtio_debugfs_dir;
+
+static int virtio_debug_device_features_show(struct seq_file *s, void *data)
+{
+	u64 device_features[VIRTIO_FEATURES_U64S];
+	struct virtio_device *dev = s->private;
+	unsigned int i;
+
+	virtio_get_features(dev, device_features);
+	for (i = 0; i < VIRTIO_FEATURES_BITS; i++) {
+		if (virtio_features_test_bit(device_features, i))
+			seq_printf(s, "%u\n", i);
+	}
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(virtio_debug_device_features);
+
+static int virtio_debug_filter_features_show(struct seq_file *s, void *data)
+{
+	struct virtio_device *dev = s->private;
+	unsigned int i;
+
+	for (i = 0; i < VIRTIO_FEATURES_BITS; i++) {
+		if (virtio_features_test_bit(dev->debugfs_filter_features, i))
+			seq_printf(s, "%u\n", i);
+	}
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(virtio_debug_filter_features);
+
+static int virtio_debug_filter_features_clear(void *data, u64 val)
+{
+	struct virtio_device *dev = data;
+
+	if (val == 1)
+		virtio_features_zero(dev->debugfs_filter_features);
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(virtio_debug_filter_features_clear_fops, NULL,
+			 virtio_debug_filter_features_clear, "%llu\n");
+
+static int virtio_debug_filter_feature_add(void *data, u64 val)
+{
+	struct virtio_device *dev = data;
+
+	if (val >= VIRTIO_FEATURES_BITS)
+		return -EINVAL;
+
+	virtio_features_set_bit(dev->debugfs_filter_features, val);
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(virtio_debug_filter_feature_add_fops, NULL,
+			 virtio_debug_filter_feature_add, "%llu\n");
+
+static int virtio_debug_filter_feature_del(void *data, u64 val)
+{
+	struct virtio_device *dev = data;
+
+	if (val >= VIRTIO_FEATURES_BITS)
+		return -EINVAL;
+
+	virtio_features_clear_bit(dev->debugfs_filter_features, val);
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(virtio_debug_filter_feature_del_fops, NULL,
+			 virtio_debug_filter_feature_del, "%llu\n");
+
+void virtio_debug_device_init(struct virtio_device *dev)
+{
+	dev->debugfs_dir = debugfs_create_dir(dev_name(&dev->dev),
+					      virtio_debugfs_dir);
+	debugfs_create_file("device_features", 0400, dev->debugfs_dir, dev,
+			    &virtio_debug_device_features_fops);
+	debugfs_create_file("filter_features", 0400, dev->debugfs_dir, dev,
+			    &virtio_debug_filter_features_fops);
+	debugfs_create_file("filter_features_clear", 0200, dev->debugfs_dir, dev,
+			    &virtio_debug_filter_features_clear_fops);
+	debugfs_create_file("filter_feature_add", 0200, dev->debugfs_dir, dev,
+			    &virtio_debug_filter_feature_add_fops);
+	debugfs_create_file("filter_feature_del", 0200, dev->debugfs_dir, dev,
+			    &virtio_debug_filter_feature_del_fops);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_device_init);
+
+void virtio_debug_device_filter_features(struct virtio_device *dev)
+{
+	virtio_features_andnot(dev->features_array, dev->features_array,
+			       dev->debugfs_filter_features);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_device_filter_features);
+
+void virtio_debug_device_exit(struct virtio_device *dev)
+{
+	debugfs_remove_recursive(dev->debugfs_dir);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_device_exit);
+
+void virtio_debug_init(void)
+{
+	virtio_debugfs_dir = debugfs_create_dir("virtio", NULL);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_init);
+
+void virtio_debug_exit(void)
+{
+	debugfs_remove_recursive(virtio_debugfs_dir);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_exit);