[RFC PATCH 1/4] cxl/region: Add region creation ABI

[Ben Widawsky <ben.widawsky@intel.com>]

Regions are created as a child of the decoder that encompasses an
address space with constraints. Regions only exist for persistent
capacities.

As an example, creating a region with:
echo 1 > /sys/bus/cxl/devices/decoder1.0/create_region

Will yield /sys/bus/cxl/devices/decoder1.0/region1.0:0

That region may then be deleted with:
echo "region1.0:0 > /sys/bus/cxl/devices/decoder1.0/delete_region

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
---
 Documentation/ABI/testing/sysfs-bus-cxl       |  19 +++
 .../driver-api/cxl/memory-devices.rst         |   8 +
 drivers/cxl/Makefile                          |   2 +-
 drivers/cxl/core.c                            |  71 ++++++++
 drivers/cxl/cxl.h                             |  11 ++
 drivers/cxl/mem.h                             |  19 +++
 drivers/cxl/region.c                          | 155 ++++++++++++++++++
 7 files changed, 284 insertions(+), 1 deletion(-)
 create mode 100644 drivers/cxl/region.c

diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
index 0b6a2e6e8fbb..5bcbefd4ea38 100644
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -127,3 +127,22 @@ Description:
 		memory (type-3). The 'target_type' attribute indicates the
 		current setting which may dynamically change based on what
 		memory regions are activated in this decode hierarchy.
+
+What:		/sys/bus/cxl/devices/decoderX.Y/create_region
+Date:		June, 2021
+KernelVersion:	v5.14
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		Writing a value of '1' will create a new uninitialized region
+		that will be mapped by the CXL decoderX.Y. Reading from this
+		node will return the last created region. Regions must be
+		subsequently configured and bound to a region driver before they
+		can be used.
+
+What:		/sys/bus/cxl/devices/decoderX.Y/delete_region
+Date:		June, 2021
+KernelVersion:	v5.14
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		Deletes the named region. A region must be unbound from the
+		region driver before being deleted.
diff --git a/Documentation/driver-api/cxl/memory-devices.rst b/Documentation/driver-api/cxl/memory-devices.rst
index 487ce4f41d77..3066638b087f 100644
--- a/Documentation/driver-api/cxl/memory-devices.rst
+++ b/Documentation/driver-api/cxl/memory-devices.rst
@@ -39,6 +39,14 @@ CXL Core
 .. kernel-doc:: drivers/cxl/core.c
    :doc: cxl core
 
+CXL Regions
+-----------
+.. kernel-doc:: drivers/cxl/region.c
+   :doc: cxl region
+
+.. kernel-doc:: drivers/cxl/region.c
+   :identifiers:
+
 External Interfaces
 ===================
 
diff --git a/drivers/cxl/Makefile b/drivers/cxl/Makefile
index a29efb3e8ad2..2b9dd9187788 100644
--- a/drivers/cxl/Makefile
+++ b/drivers/cxl/Makefile
@@ -4,6 +4,6 @@ obj-$(CONFIG_CXL_MEM) += cxl_pci.o
 obj-$(CONFIG_CXL_ACPI) += cxl_acpi.o
 
 ccflags-y += -DDEFAULT_SYMBOL_NAMESPACE=CXL
-cxl_core-y := core.o
+cxl_core-y := core.o region.o
 cxl_pci-y := pci.o
 cxl_acpi-y := acpi.o
diff --git a/drivers/cxl/core.c b/drivers/cxl/core.c
index 1b9ee0b08384..cda09a9cd98e 100644
--- a/drivers/cxl/core.c
+++ b/drivers/cxl/core.c
@@ -7,6 +7,7 @@
 #include <linux/slab.h>
 #include <linux/idr.h>
 #include "cxl.h"
+#include "mem.h"
 
 /**
  * DOC: cxl core
@@ -119,7 +120,68 @@ static ssize_t target_list_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(target_list);
 
+static ssize_t create_region_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct cxl_decoder *cxld = to_cxl_decoder(dev);
+	int rc;
+
+	device_lock(dev);
+	rc = sprintf(buf, "%s\n",
+		     cxld->youngest ? dev_name(&cxld->youngest->dev) : "");
+	device_unlock(dev);
+
+	return rc;
+}
+
+static ssize_t create_region_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t len)
+{
+	struct cxl_decoder *cxld = to_cxl_decoder(dev);
+	struct cxl_region *region;
+	ssize_t rc;
+	int val;
+
+	rc = kstrtoint(buf, 0, &val);
+	if (rc)
+		return rc;
+	if (val != 1)
+		return -EINVAL;
+
+	region = cxl_alloc_region(cxld);
+	if (IS_ERR(region))
+		return PTR_ERR(region);
+
+	rc = cxl_add_region(cxld, region);
+	if (rc) {
+		cxl_free_region(cxld, region);
+		return rc;
+	}
+
+	cxld->youngest = region;
+	return len;
+}
+static DEVICE_ATTR_RW(create_region);
+
+static ssize_t delete_region_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t len)
+{
+	struct cxl_decoder *cxld = to_cxl_decoder(dev);
+	int rc;
+
+	rc = cxl_delete_region(cxld, buf);
+	if (rc)
+		return rc;
+
+	return len;
+}
+static DEVICE_ATTR_WO(delete_region);
+
 static struct attribute *cxl_decoder_base_attrs[] = {
+	&dev_attr_create_region.attr,
+	&dev_attr_delete_region.attr,
 	&dev_attr_start.attr,
 	&dev_attr_size.attr,
 	&dev_attr_locked.attr,
@@ -170,7 +232,13 @@ static void cxl_decoder_release(struct device *dev)
 {
 	struct cxl_decoder *cxld = to_cxl_decoder(dev);
 	struct cxl_port *port = to_cxl_port(dev->parent);
+	struct cxl_region *region;
 
+	list_for_each_entry(region, &cxld->regions, list) {
+		cxl_delete_region(cxld, dev_name(&region->dev));
+	}
+	dev_WARN_ONCE(dev, !ida_is_empty(&cxld->region_ida),
+		      "Lost track of a region");
 	ida_free(&port->decoder_ida, cxld->id);
 	kfree(cxld);
 }
@@ -475,8 +543,11 @@ cxl_decoder_alloc(struct cxl_port *port, int nr_targets, resource_size_t base,
 		.interleave_ways = interleave_ways,
 		.interleave_granularity = interleave_granularity,
 		.target_type = type,
+		.regions = LIST_HEAD_INIT(cxld->regions),
 	};
 
+	ida_init(&cxld->region_ida);
+
 	/* handle implied target_list */
 	if (interleave_ways == 1)
 		cxld->target[0] =
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index b988ea288f53..1ffc5e07e24d 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -7,6 +7,7 @@
 #include <linux/bitfield.h>
 #include <linux/bitops.h>
 #include <linux/io.h>
+#include <linux/uuid.h>
 
 /**
  * DOC: cxl objects
@@ -182,6 +183,9 @@ enum cxl_decoder_type {
  * @interleave_granularity: data stride per dport
  * @target_type: accelerator vs expander (type2 vs type3) selector
  * @flags: memory type capabilities and locking
+ * @region_ida: allocator for region ids.
+ * @regions: List of regions mapped (may be disabled) by this decoder.
+ * @youngest: Last region created for this decoder.
  * @target: active ordered target list in current decoder configuration
  */
 struct cxl_decoder {
@@ -192,6 +196,9 @@ struct cxl_decoder {
 	int interleave_granularity;
 	enum cxl_decoder_type target_type;
 	unsigned long flags;
+	struct ida region_ida;
+	struct list_head regions;
+	struct cxl_region *youngest;
 	struct cxl_dport *target[];
 };
 
@@ -231,6 +238,10 @@ struct cxl_dport {
 	struct list_head list;
 };
 
+struct cxl_region *cxl_alloc_region(struct cxl_decoder *cxld);
+void cxl_free_region(struct cxl_decoder *cxld, struct cxl_region *region);
+int cxl_add_region(struct cxl_decoder *cxld, struct cxl_region *region);
+int cxl_delete_region(struct cxl_decoder *cxld, const char *region);
 struct cxl_port *to_cxl_port(struct device *dev);
 struct cxl_port *devm_cxl_add_port(struct device *host, struct device *uport,
 				   resource_size_t component_reg_phys,
diff --git a/drivers/cxl/mem.h b/drivers/cxl/mem.h
index 13868ff7cadf..4c4eb06a966b 100644
--- a/drivers/cxl/mem.h
+++ b/drivers/cxl/mem.h
@@ -3,6 +3,8 @@
 #ifndef __CXL_MEM_H__
 #define __CXL_MEM_H__
 
+#include <linux/cdev.h>
+
 /* CXL 2.0 8.2.8.5.1.1 Memory Device Status Register */
 #define CXLMDEV_STATUS_OFFSET 0x0
 #define   CXLMDEV_DEV_FATAL BIT(0)
@@ -46,6 +48,23 @@ struct cxl_memdev {
 	int id;
 };
 
+/**
+ * struct cxl_region - CXL region
+ * @dev: This region's device.
+ * @id: This regions id. Id is globally unique across all regions.
+ * @res: Address space consumed by this region.
+ * @list: Node in decoders region list.
+ * @targets: The memory devices comprising the region.
+ */
+struct cxl_region {
+	struct device dev;
+	int id;
+	struct resource res;
+	struct list_head list;
+	struct cxl_memdev *targets[];
+};
+
+
 /**
  * struct cxl_mem - A CXL memory device
  * @pdev: The PCI device associated with this CXL device.
diff --git a/drivers/cxl/region.c b/drivers/cxl/region.c
new file mode 100644
index 000000000000..1f47bc17bd50
--- /dev/null
+++ b/drivers/cxl/region.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2021 Intel Corporation. All rights reserved. */
+#include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/idr.h>
+#include "cxl.h"
+#include "mem.h"
+
+/**
+ * DOC: cxl region
+ *
+ * A CXL region encompasses a chunk of host physical address space that may be
+ * consumed by a single device (x1 interleave aka linear) or across multiple
+ * devices (xN interleaved). A region is a child device of a &struct
+ * cxl_decoder. There may be multiple active regions under a single &struct
+ * cxl_decoder. The common case for multiple regions would be several linear,
+ * contiguous regions under a single decoder. Generally, there will be a 1:1
+ * relationship between decoder and region when the region is interleaved.
+ */
+
+static void cxl_region_release(struct device *dev);
+
+static const struct device_type cxl_region_type = {
+	.name = "cxl_region",
+	.release = cxl_region_release,
+};
+
+static struct cxl_region *to_cxl_region(struct device *dev)
+{
+	if (dev_WARN_ONCE(dev, dev->type != &cxl_region_type,
+			  "not a cxl_region device\n"))
+		return NULL;
+
+	return container_of(dev, struct cxl_region, dev);
+}
+
+void cxl_free_region(struct cxl_decoder *cxld, struct cxl_region *region)
+{
+	ida_free(&cxld->region_ida, region->id);
+	kfree(region->targets);
+	kfree(region);
+}
+
+static void cxl_region_release(struct device *dev)
+{
+	struct cxl_decoder *cxld = to_cxl_decoder(dev->parent);
+	struct cxl_region *region;
+
+	region = to_cxl_region(dev);
+	cxl_free_region(cxld, region);
+}
+
+struct cxl_region *cxl_alloc_region(struct cxl_decoder *cxld)
+{
+	struct cxl_region *region;
+	int rc;
+
+	region = kzalloc(struct_size(region, targets, cxld->interleave_ways),
+			 GFP_KERNEL);
+	if (!region) {
+		pr_err("No memory\n");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	rc = ida_alloc(&cxld->region_ida, GFP_KERNEL);
+	if (rc < 0) {
+		dev_err(&cxld->dev, "Couldn't get a new id\n");
+		kfree(region);
+		return ERR_PTR(rc);
+	}
+	region->id = rc;
+
+	return region;
+}
+
+/**
+ * cxl_add_region - Adds a region to a decoder
+ * @cxld: Parent decoder.
+ * @region: Region to be added to the decoder.
+ *
+ * This is the second step of region initialization. Regions exist within an
+ * address space which is mapped by a @cxld, and that @cxld enforces constraints
+ * upon the region as it is configured. Regions may be added to a @cxld but not
+ * activated and therefore it is possible to have more regions in a @cxld than
+ * there are interleave ways in the @cxld. Regions exist only for persistent
+ * capacities.
+ *
+ * Return: zero if the region was added to the @cxld, else returns negative
+ * error code.
+ */
+int cxl_add_region(struct cxl_decoder *cxld, struct cxl_region *region)
+{
+	struct cxl_port *port = to_cxl_port(cxld->dev.parent);
+	struct device *dev = &region->dev;
+	struct resource *res;
+	int rc;
+
+	device_initialize(dev);
+	dev->parent = &cxld->dev;
+	dev->bus = &cxl_bus_type;
+	dev->type = &cxl_region_type;
+	rc = dev_set_name(dev, "region%d.%d:%d", port->id, cxld->id, region->id);
+	if (rc)
+		goto err;
+
+	rc = device_add(dev);
+	if (rc)
+		goto err;
+
+	res = &region->res;
+	res->name = "Persistent Memory";
+	res->start = 0;
+	res->end = -1;
+	res->flags = IORESOURCE_MEM;
+	res->desc = IORES_DESC_PERSISTENT_MEMORY;
+
+	dev_dbg(dev, "Added %s to %s\n", dev_name(dev), dev_name(&cxld->dev));
+
+	return 0;
+
+err:
+	put_device(dev);
+	return rc;
+}
+
+static struct cxl_region *
+cxl_find_region_by_name(struct cxl_decoder *cxld, const char *name)
+{
+	struct device *region_dev;
+
+	region_dev = device_find_child_by_name(&cxld->dev, name);
+	if (!region_dev)
+		return ERR_PTR(-ENOENT);
+
+	return to_cxl_region(region_dev);
+}
+
+int cxl_delete_region(struct cxl_decoder *cxld, const char *region_name)
+{
+	struct cxl_region *region;
+
+	region = cxl_find_region_by_name(cxld, region_name);
+	if (IS_ERR(region))
+		return PTR_ERR(region);
+
+	dev_dbg(&cxld->dev, "Requested removal of %s from %s\n",
+		dev_name(&region->dev), dev_name(&cxld->dev));
+
+	device_unregister(&region->dev);
+	put_device(&region->dev);
+
+	return 0;
+}
-- 
2.32.0