cxl/core: Move memdev management to core

The motivation for moving cxl_memdev allocation to the core (beyond
better file organization of sysfs attributes in core/ and drivers in
cxl/), is that device lifetime is longer than module lifetime. The cxl_pci
module should be free to come and go without needing to coordinate with
devices that need the text associated with cxl_memdev_release() to stay
resident. The move fixes a use after free bug when looping driver
load / unload with CONFIG_DEBUG_KOBJECT_RELEASE=y.

Another motivation for disconnecting cxl_memdev creation from cxl_pci is
to enable other drivers, like a unit test driver, to registers memdevs.

Fixes: b39cb10 ("cxl/mem: Register CXL memX devices")
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/162792540495.368511.9748638751088219595.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/Makefile

@@ -5,3 +5,4 @@ ccflags-y += -DDEFAULT_SYMBOL_NAMESPACE=CXL -I$(srctree)/drivers/cxl
 cxl_core-y := bus.o
 cxl_core-y += pmem.o
 cxl_core-y += regs.o
+cxl_core-y += memdev.o

drivers/cxl/core/bus.c

@@ -634,12 +634,26 @@ EXPORT_SYMBOL_GPL(cxl_bus_type);
 
 static __init int cxl_core_init(void)
 {
-	return bus_register(&cxl_bus_type);
+	int rc;
+
+	rc = cxl_memdev_init();
+	if (rc)
+		return rc;
+
+	rc = bus_register(&cxl_bus_type);
+	if (rc)
+		goto err;
+	return 0;
+
+err:
+	cxl_memdev_exit();
+	return rc;
 }
 
 static void cxl_core_exit(void)
 {
 	bus_unregister(&cxl_bus_type);
+	cxl_memdev_exit();
 }
 
 module_init(cxl_core_init);

drivers/cxl/core/core.h

@@ -14,4 +14,7 @@ static inline void unregister_cxl_dev(void *dev)
 	device_unregister(dev);
 }
 
+int cxl_memdev_init(void);
+void cxl_memdev_exit(void);
+
 #endif /* __CXL_CORE_H__ */

drivers/cxl/core/memdev.c

@@ -0,0 +1,246 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2020 Intel Corporation. */
+
+#include <linux/device.h>
+#include <linux/slab.h>
+#include <linux/idr.h>
+#include <linux/pci.h>
+#include <cxlmem.h>
+#include "core.h"
+
+/*
+ * An entire PCI topology full of devices should be enough for any
+ * config
+ */
+#define CXL_MEM_MAX_DEVS 65536
+
+static int cxl_mem_major;
+static DEFINE_IDA(cxl_memdev_ida);
+
+static void cxl_memdev_release(struct device *dev)
+{
+	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+
+	ida_free(&cxl_memdev_ida, cxlmd->id);
+	kfree(cxlmd);
+}
+
+static char *cxl_memdev_devnode(struct device *dev, umode_t *mode, kuid_t *uid,
+				kgid_t *gid)
+{
+	return kasprintf(GFP_KERNEL, "cxl/%s", dev_name(dev));
+}
+
+static ssize_t firmware_version_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+	struct cxl_mem *cxlm = cxlmd->cxlm;
+
+	return sysfs_emit(buf, "%.16s\n", cxlm->firmware_version);
+}
+static DEVICE_ATTR_RO(firmware_version);
+
+static ssize_t payload_max_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+	struct cxl_mem *cxlm = cxlmd->cxlm;
+
+	return sysfs_emit(buf, "%zu\n", cxlm->payload_size);
+}
+static DEVICE_ATTR_RO(payload_max);
+
+static ssize_t label_storage_size_show(struct device *dev,
+				       struct device_attribute *attr, char *buf)
+{
+	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+	struct cxl_mem *cxlm = cxlmd->cxlm;
+
+	return sysfs_emit(buf, "%zu\n", cxlm->lsa_size);
+}
+static DEVICE_ATTR_RO(label_storage_size);
+
+static ssize_t ram_size_show(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+	struct cxl_mem *cxlm = cxlmd->cxlm;
+	unsigned long long len = range_len(&cxlm->ram_range);
+
+	return sysfs_emit(buf, "%#llx\n", len);
+}
+
+static struct device_attribute dev_attr_ram_size =
+	__ATTR(size, 0444, ram_size_show, NULL);
+
+static ssize_t pmem_size_show(struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+	struct cxl_mem *cxlm = cxlmd->cxlm;
+	unsigned long long len = range_len(&cxlm->pmem_range);
+
+	return sysfs_emit(buf, "%#llx\n", len);
+}
+
+static struct device_attribute dev_attr_pmem_size =
+	__ATTR(size, 0444, pmem_size_show, NULL);
+
+static struct attribute *cxl_memdev_attributes[] = {
+	&dev_attr_firmware_version.attr,
+	&dev_attr_payload_max.attr,
+	&dev_attr_label_storage_size.attr,
+	NULL,
+};
+
+static struct attribute *cxl_memdev_pmem_attributes[] = {
+	&dev_attr_pmem_size.attr,
+	NULL,
+};
+
+static struct attribute *cxl_memdev_ram_attributes[] = {
+	&dev_attr_ram_size.attr,
+	NULL,
+};
+
+static struct attribute_group cxl_memdev_attribute_group = {
+	.attrs = cxl_memdev_attributes,
+};
+
+static struct attribute_group cxl_memdev_ram_attribute_group = {
+	.name = "ram",
+	.attrs = cxl_memdev_ram_attributes,
+};
+
+static struct attribute_group cxl_memdev_pmem_attribute_group = {
+	.name = "pmem",
+	.attrs = cxl_memdev_pmem_attributes,
+};
+
+static const struct attribute_group *cxl_memdev_attribute_groups[] = {
+	&cxl_memdev_attribute_group,
+	&cxl_memdev_ram_attribute_group,
+	&cxl_memdev_pmem_attribute_group,
+	NULL,
+};
+
+static const struct device_type cxl_memdev_type = {
+	.name = "cxl_memdev",
+	.release = cxl_memdev_release,
+	.devnode = cxl_memdev_devnode,
+	.groups = cxl_memdev_attribute_groups,
+};
+
+static void cxl_memdev_unregister(void *_cxlmd)
+{
+	struct cxl_memdev *cxlmd = _cxlmd;
+	struct device *dev = &cxlmd->dev;
+	struct cdev *cdev = &cxlmd->cdev;
+	const struct cdevm_file_operations *cdevm_fops;
+
+	cdevm_fops = container_of(cdev->ops, typeof(*cdevm_fops), fops);
+	cdevm_fops->shutdown(dev);
+
+	cdev_device_del(&cxlmd->cdev, dev);
+	put_device(dev);
+}
+
+static struct cxl_memdev *cxl_memdev_alloc(struct cxl_mem *cxlm,
+					   const struct file_operations *fops)
+{
+	struct pci_dev *pdev = cxlm->pdev;
+	struct cxl_memdev *cxlmd;
+	struct device *dev;
+	struct cdev *cdev;
+	int rc;
+
+	cxlmd = kzalloc(sizeof(*cxlmd), GFP_KERNEL);
+	if (!cxlmd)
+		return ERR_PTR(-ENOMEM);
+
+	rc = ida_alloc_range(&cxl_memdev_ida, 0, CXL_MEM_MAX_DEVS, GFP_KERNEL);
+	if (rc < 0)
+		goto err;
+	cxlmd->id = rc;
+
+	dev = &cxlmd->dev;
+	device_initialize(dev);
+	dev->parent = &pdev->dev;
+	dev->bus = &cxl_bus_type;
+	dev->devt = MKDEV(cxl_mem_major, cxlmd->id);
+	dev->type = &cxl_memdev_type;
+	device_set_pm_not_required(dev);
+
+	cdev = &cxlmd->cdev;
+	cdev_init(cdev, fops);
+	return cxlmd;
+
+err:
+	kfree(cxlmd);
+	return ERR_PTR(rc);
+}
+
+struct cxl_memdev *
+devm_cxl_add_memdev(struct device *host, struct cxl_mem *cxlm,
+		    const struct cdevm_file_operations *cdevm_fops)
+{
+	struct cxl_memdev *cxlmd;
+	struct device *dev;
+	struct cdev *cdev;
+	int rc;
+
+	cxlmd = cxl_memdev_alloc(cxlm, &cdevm_fops->fops);
+	if (IS_ERR(cxlmd))
+		return cxlmd;
+
+	dev = &cxlmd->dev;
+	rc = dev_set_name(dev, "mem%d", cxlmd->id);
+	if (rc)
+		goto err;
+
+	/*
+	 * Activate ioctl operations, no cxl_memdev_rwsem manipulation
+	 * needed as this is ordered with cdev_add() publishing the device.
+	 */
+	cxlmd->cxlm = cxlm;
+
+	cdev = &cxlmd->cdev;
+	rc = cdev_device_add(cdev, dev);
+	if (rc)
+		goto err;
+
+	rc = devm_add_action_or_reset(host, cxl_memdev_unregister, cxlmd);
+	if (rc)
+		return ERR_PTR(rc);
+	return cxlmd;
+
+err:
+	/*
+	 * The cdev was briefly live, shutdown any ioctl operations that
+	 * saw that state.
+	 */
+	cdevm_fops->shutdown(dev);
+	put_device(dev);
+	return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_GPL(devm_cxl_add_memdev);
+
+__init int cxl_memdev_init(void)
+{
+	dev_t devt;
+	int rc;
+
+	rc = alloc_chrdev_region(&devt, 0, CXL_MEM_MAX_DEVS, "cxl");
+	if (rc)
+		return rc;
+
+	cxl_mem_major = MAJOR(devt);
+
+	return 0;
+}
+
+void cxl_memdev_exit(void)
+{
+	unregister_chrdev_region(MKDEV(cxl_mem_major, 0), CXL_MEM_MAX_DEVS);
+}

drivers/cxl/cxlmem.h

@@ -28,12 +28,6 @@
 	(FIELD_GET(CXLMDEV_RESET_NEEDED_MASK, status) !=                       \
 	 CXLMDEV_RESET_NEEDED_NOT)
 
-/*
- * An entire PCI topology full of devices should be enough for any
- * config
- */
-#define CXL_MEM_MAX_DEVS 65536
-
 /**
  * struct cdevm_file_operations - devm coordinated cdev file operations
  * @fops: file operations that are synchronized against @shutdown
@@ -63,6 +57,15 @@ struct cxl_memdev {
 	int id;
 };
 
+static inline struct cxl_memdev *to_cxl_memdev(struct device *dev)
+{
+	return container_of(dev, struct cxl_memdev, dev);
+}
+
+struct cxl_memdev *
+devm_cxl_add_memdev(struct device *host, struct cxl_mem *cxlm,
+		    const struct cdevm_file_operations *cdevm_fops);
+
 /**
  * struct cxl_mem - A CXL memory device
  * @pdev: The PCI device associated with this CXL device.