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, 81 insertions, 0 deletions

diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h
new file mode 100644
index 000000000..bfc31923f
--- /dev/null
+++ b/drivers/dax/bus.h
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2016 - 2018 Intel Corporation. All rights reserved. */
+#ifndef __DAX_BUS_H__
+#define __DAX_BUS_H__
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/range.h>
+#include <linux/workqueue.h>
+
+struct dev_dax;
+struct resource;
+struct dax_device;
+struct dax_region;
+
+/* dax bus specific ioresource flags */
+#define IORESOURCE_DAX_STATIC BIT(0)
+#define IORESOURCE_DAX_KMEM BIT(1)
+
+#define DAX_KMEM_UNPLUGGED	(-1) /* Do not create memory blocks */
+
+struct dax_region *alloc_dax_region(struct device *parent, int region_id,
+		struct range *range, int target_node, unsigned int align,
+		unsigned long flags);
+
+struct dev_dax_data {
+	struct dax_region *dax_region;
+	struct dev_pagemap *pgmap;
+	resource_size_t size;
+	int id;
+	bool memmap_on_memory;
+};
+
+struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data);
+
+enum dax_driver_type {
+	DAXDRV_KMEM_TYPE,
+	DAXDRV_DEVICE_TYPE,
+	DAXDRV_FSDEV_TYPE,
+};
+
+struct dax_device_driver {
+	struct device_driver drv;
+	struct list_head ids;
+	enum dax_driver_type type;
+	int (*probe)(struct dev_dax *dev);
+	void (*remove)(struct dev_dax *dev);
+};
+
+#define to_dax_drv(__drv) container_of_const(__drv, struct dax_device_driver, drv)
+
+int __dax_driver_register(struct dax_device_driver *dax_drv,
+		struct module *module, const char *mod_name);
+#define dax_driver_register(driver) \
+	__dax_driver_register(driver, THIS_MODULE, KBUILD_MODNAME)
+void dax_driver_unregister(struct dax_device_driver *dax_drv);
+void kill_dev_dax(struct dev_dax *dev_dax);
+bool static_dev_dax(struct dev_dax *dev_dax);
+
+struct hmem_platform_device {
+	struct platform_device pdev;
+	struct work_struct work;
+	bool did_probe;
+};
+
+static inline struct hmem_platform_device *
+to_hmem_platform_device(struct platform_device *pdev)
+{
+	return container_of(pdev, struct hmem_platform_device, pdev);
+}
+
+#if IS_ENABLED(CONFIG_DEV_DAX_HMEM)
+void dax_hmem_flush_work(void);
+#else
+static inline void dax_hmem_flush_work(void) { }
+#endif
+
+#define MODULE_ALIAS_DAX_DEVICE(type) \
+	MODULE_ALIAS("dax:t" __stringify(type) "*")
+#define DAX_DEVICE_MODALIAS_FMT "dax:t%d"
+
+#endif /* __DAX_BUS_H__ */