1 files changed, 313 insertions, 0 deletions
diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
new file mode 100644
index 000000000000..c036e4d0b610
--- /dev/null
+++ b/drivers/dax/kmem.c
@@ -0,0 +1,313 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2016-2019 Intel Corporation. All rights reserved. */
+#include <linux/memremap.h>
+#include <linux/pagemap.h>
+#include <linux/memory.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/slab.h>
+#include <linux/dax.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/memory-tiers.h>
+#include <linux/memory_hotplug.h>
+#include <linux/string_helpers.h>
+#include "dax-private.h"
+#include "bus.h"
+
+/*
+ * Default abstract distance assigned to the NUMA node onlined
+ * by DAX/kmem if the low level platform driver didn't initialize
+ * one for this NUMA node.
+ */
+#define MEMTIER_DEFAULT_DAX_ADISTANCE	(MEMTIER_ADISTANCE_DRAM * 5)
+
+/* Memory resource name used for add_memory_driver_managed(). */
+static const char *kmem_name;
+/* Set if any memory will remain added when the driver will be unloaded. */
+static bool any_hotremove_failed;
+
+static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r)
+{
+	struct dev_dax_range *dax_range = &dev_dax->ranges[i];
+	struct range *range = &dax_range->range;
+
+	/* memory-block align the hotplug range */
+	r->start = ALIGN(range->start, memory_block_size_bytes());
+	r->end = ALIGN_DOWN(range->end + 1, memory_block_size_bytes()) - 1;
+	if (r->start >= r->end) {
+		r->start = range->start;
+		r->end = range->end;
+		return -ENOSPC;
+	}
+	return 0;
+}
+
+struct dax_kmem_data {
+	const char *res_name;
+	int mgid;
+	struct resource *res[];
+};
+
+static DEFINE_MUTEX(kmem_memory_type_lock);
+static LIST_HEAD(kmem_memory_types);
+
+static struct memory_dev_type *kmem_find_alloc_memory_type(int adist)
+{
+	guard(mutex)(&kmem_memory_type_lock);
+	return mt_find_alloc_memory_type(adist, &kmem_memory_types);
+}
+
+static void kmem_put_memory_types(void)
+{
+	guard(mutex)(&kmem_memory_type_lock);
+	mt_put_memory_types(&kmem_memory_types);
+}
+
+static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
+{
+	struct device *dev = &dev_dax->dev;
+	unsigned long total_len = 0, orig_len = 0;
+	struct dax_kmem_data *data;
+	struct memory_dev_type *mtype;
+	int i, rc, mapped = 0;
+	mhp_t mhp_flags;
+	int numa_node;
+	int adist = MEMTIER_DEFAULT_DAX_ADISTANCE;
+
+	/*
+	 * Ensure good NUMA information for the persistent memory.
+	 * Without this check, there is a risk that slow memory
+	 * could be mixed in a node with faster memory, causing
+	 * unavoidable performance issues.
+	 */
+	numa_node = dev_dax->target_node;
+	if (numa_node < 0) {
+		dev_warn(dev, "rejecting DAX region with invalid node: %d\n",
+				numa_node);
+		return -EINVAL;
+	}
+
+	mt_calc_adistance(numa_node, &adist);
+	mtype = kmem_find_alloc_memory_type(adist);
+	if (IS_ERR(mtype))
+		return PTR_ERR(mtype);
+
+	for (i = 0; i < dev_dax->nr_range; i++) {
+		struct range range;
+
+		orig_len += range_len(&dev_dax->ranges[i].range);
+		rc = dax_kmem_range(dev_dax, i, &range);
+		if (rc) {
+			dev_info(dev, "mapping%d: %#llx-%#llx too small after alignment\n",
+					i, range.start, range.end);
+			continue;
+		}
+		total_len += range_len(&range);
+	}
+
+	if (!total_len) {
+		dev_warn(dev, "rejecting DAX region without any memory after alignment\n");
+		return -EINVAL;
+	} else if (total_len != orig_len) {
+		char buf[16];
+
+		string_get_size(orig_len - total_len, 1, STRING_UNITS_2,
+				buf, sizeof(buf));
+		dev_warn(dev, "DAX region truncated by %s due to alignment\n", buf);
+	}
+
+	init_node_memory_type(numa_node, mtype);
+
+	rc = -ENOMEM;
+	data = kzalloc(struct_size(data, res, dev_dax->nr_range), GFP_KERNEL);
+	if (!data)
+		goto err_dax_kmem_data;
+
+	data->res_name = kstrdup(dev_name(dev), GFP_KERNEL);
+	if (!data->res_name)
+		goto err_res_name;
+
+	rc = memory_group_register_static(numa_node, PFN_UP(total_len));
+	if (rc < 0)
+		goto err_reg_mgid;
+	data->mgid = rc;
+
+	for (i = 0; i < dev_dax->nr_range; i++) {
+		struct resource *res;
+		struct range range;
+
+		rc = dax_kmem_range(dev_dax, i, &range);
+		if (rc)
+			continue;
+
+		/* Region is permanently reserved if hotremove fails. */
+		res = request_mem_region(range.start, range_len(&range), data->res_name);
+		if (!res) {
+			dev_warn(dev, "mapping%d: %#llx-%#llx could not reserve region\n",
+					i, range.start, range.end);
+			/*
+			 * Once some memory has been onlined we can't
+			 * assume that it can be un-onlined safely.
+			 */
+			if (mapped)
+				continue;
+			rc = -EBUSY;
+			goto err_request_mem;
+		}
+		data->res[i] = res;
+
+		/*
+		 * Set flags appropriate for System RAM.  Leave ..._BUSY clear
+		 * so that add_memory() can add a child resource.  Do not
+		 * inherit flags from the parent since it may set new flags
+		 * unknown to us that will break add_memory() below.
+		 */
+		res->flags = IORESOURCE_SYSTEM_RAM;
+
+		mhp_flags = MHP_NID_IS_MGID;
+		if (dev_dax->memmap_on_memory)
+			mhp_flags |= MHP_MEMMAP_ON_MEMORY;
+
+		/*
+		 * Ensure that future kexec'd kernels will not treat
+		 * this as RAM automatically.
+		 */
+		rc = add_memory_driver_managed(data->mgid, range.start,
+				range_len(&range), kmem_name, mhp_flags);
+
+		if (rc) {
+			dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n",
+					i, range.start, range.end);
+			remove_resource(res);
+			kfree(res);
+			data->res[i] = NULL;
+			if (mapped)
+				continue;
+			goto err_request_mem;
+		}
+		mapped++;
+	}
+
+	dev_set_drvdata(dev, data);
+
+	return 0;
+
+err_request_mem:
+	memory_group_unregister(data->mgid);
+err_reg_mgid:
+	kfree(data->res_name);
+err_res_name:
+	kfree(data);
+err_dax_kmem_data:
+	clear_node_memory_type(numa_node, mtype);
+	return rc;
+}
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
+{
+	int i, success = 0;
+	int node = dev_dax->target_node;
+	struct device *dev = &dev_dax->dev;
+	struct dax_kmem_data *data = dev_get_drvdata(dev);
+
+	/*
+	 * We have one shot for removing memory, if some memory blocks were not
+	 * offline prior to calling this function remove_memory() will fail, and
+	 * there is no way to hotremove this memory until reboot because device
+	 * unbind will succeed even if we return failure.
+	 */
+	for (i = 0; i < dev_dax->nr_range; i++) {
+		struct range range;
+		int rc;
+
+		rc = dax_kmem_range(dev_dax, i, &range);
+		if (rc)
+			continue;
+
+		rc = remove_memory(range.start, range_len(&range));
+		if (rc == 0) {
+			remove_resource(data->res[i]);
+			kfree(data->res[i]);
+			data->res[i] = NULL;
+			success++;
+			continue;
+		}
+		any_hotremove_failed = true;
+		dev_err(dev,
+			"mapping%d: %#llx-%#llx cannot be hotremoved until the next reboot\n",
+				i, range.start, range.end);
+	}
+
+	if (success >= dev_dax->nr_range) {
+		memory_group_unregister(data->mgid);
+		kfree(data->res_name);
+		kfree(data);
+		dev_set_drvdata(dev, NULL);
+		/*
+		 * Clear the memtype association on successful unplug.
+		 * If not, we have memory blocks left which can be
+		 * offlined/onlined later. We need to keep memory_dev_type
+		 * for that. This implies this reference will be around
+		 * till next reboot.
+		 */
+		clear_node_memory_type(node, NULL);
+	}
+}
+#else
+static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
+{
+	/*
+	 * Without hotremove purposely leak the request_mem_region() for the
+	 * device-dax range and return '0' to ->remove() attempts. The removal
+	 * of the device from the driver always succeeds, but the region is
+	 * permanently pinned as reserved by the unreleased
+	 * request_mem_region().
+	 */
+	any_hotremove_failed = true;
+}
+#endif /* CONFIG_MEMORY_HOTREMOVE */
+
+static struct dax_device_driver device_dax_kmem_driver = {
+	.probe = dev_dax_kmem_probe,
+	.remove = dev_dax_kmem_remove,
+	.type = DAXDRV_KMEM_TYPE,
+};
+
+static int __init dax_kmem_init(void)
+{
+	int rc;
+
+	/* Resource name is permanently allocated if any hotremove fails. */
+	kmem_name = kstrdup_const("System RAM (kmem)", GFP_KERNEL);
+	if (!kmem_name)
+		return -ENOMEM;
+
+	rc = dax_driver_register(&device_dax_kmem_driver);
+	if (rc)
+		goto error_dax_driver;
+
+	return rc;
+
+error_dax_driver:
+	kmem_put_memory_types();
+	kfree_const(kmem_name);
+	return rc;
+}
+
+static void __exit dax_kmem_exit(void)
+{
+	dax_driver_unregister(&device_dax_kmem_driver);
+	if (!any_hotremove_failed)
+		kfree_const(kmem_name);
+	kmem_put_memory_types();
+}
+
+MODULE_AUTHOR("Intel Corporation");
+MODULE_DESCRIPTION("KMEM DAX: map dax-devices as System-RAM");
+MODULE_LICENSE("GPL v2");
+module_init(dax_kmem_init);
+module_exit(dax_kmem_exit);
+MODULE_ALIAS_DAX_DEVICE(0);