nvdimm: allow exposing RAM carveouts as NVDIMM devicesramdax

Add a ramdax driver that creates a DIMM device on top of E820 type-12 memory carveouts and devicetree pmem-region nodes. The DIMMs support label spacce management on the "device" and provide a convenient way to access RAM carveouts using fsdax and devdax. Signed-off-by: Mike Rapoport (Mircosoft) <rppt@kernel.org>
author: Mike Rapoport (Microsoft) <rppt@kernel.org> 2025-05-11 12:51:14 +0300
committer: Mike Rapoport (Microsoft) <rppt@kernel.org> 2025-05-14 18:10:19 +0300
commit: 0b81d6e851e5acf76aba4697db1281798bedbec8 (patch)
tree: 74da229baedba3c4bde0d1f5446b2e9d20b60fd3
parent: 92a09c47464d040866cf2b4cd052bc60555185fb (diff)
download: linux-ramdax.tar.gz
3 files changed, 290 insertions, 0 deletions
diff --git a/drivers/nvdimm/Kconfig b/drivers/nvdimm/Kconfig
index fde3e17c836c83..47cd0ef64aaf03 100644
--- a/drivers/nvdimm/Kconfig
+++ b/drivers/nvdimm/Kconfig
@@ -97,6 +97,16 @@ config OF_PMEM
 
 	  Select Y if unsure.
 
+config RAMDAX
+	tristate "Support persistent memory on RAM carveouts"
+	depends on OF || (X86 && X86_PMEM_LEGACY=n)
+	select X86_PMEM_LEGACY_DEVICE
+	default LIBNVDIMM
+	help
+	  Allows creation of "peristent" memory devices on RAM carveouts.
+
+	  Select Y if unsure.
+
 config NVDIMM_KEYS
 	def_bool y
 	depends on ENCRYPTED_KEYS
diff --git a/drivers/nvdimm/Makefile b/drivers/nvdimm/Makefile
index ba0296dca9db63..8c268814936cec 100644
--- a/drivers/nvdimm/Makefile
+++ b/drivers/nvdimm/Makefile
@@ -5,6 +5,7 @@ obj-$(CONFIG_ND_BTT) += nd_btt.o
 obj-$(CONFIG_X86_PMEM_LEGACY) += nd_e820.o
 obj-$(CONFIG_OF_PMEM) += of_pmem.o
 obj-$(CONFIG_VIRTIO_PMEM) += virtio_pmem.o nd_virtio.o
+obj-$(CONFIG_RAMDAX) += ramdax.o
 
 nd_pmem-y := pmem.o
 
diff --git a/drivers/nvdimm/ramdax.c b/drivers/nvdimm/ramdax.c
new file mode 100644
index 00000000000000..e7a99d6cec3171
--- /dev/null
+++ b/drivers/nvdimm/ramdax.c
@@ -0,0 +1,279 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2015, Mike Rapoport, Microsoft
+ *
+ * Based on e820 pmem driver:
+ * Copyright (c) 2015, Christoph Hellwig.
+ * Copyright (c) 2015, Intel Corporation.
+ */
+#include <linux/platform_device.h>
+#include <linux/memory_hotplug.h>
+#include <linux/libnvdimm.h>
+#include <linux/module.h>
+#include <linux/numa.h>
+#include <linux/io.h>
+#include <linux/of.h>
+
+#include <uapi/linux/ndctl.h>
+
+#define LABEL_AREA_SIZE	SZ_128K
+
+struct ramdax_dimm {
+	struct nvdimm *nvdimm;
+	void *label_area;
+};
+
+static void ramdax_remove(struct platform_device *pdev)
+{
+	struct nvdimm_bus *nvdimm_bus = platform_get_drvdata(pdev);
+
+	/* FIXME: cleanup dimm and region devices */
+
+	nvdimm_bus_unregister(nvdimm_bus);
+}
+
+static int ramdax_register_region(struct resource *res,
+				    struct nvdimm *nvdimm,
+				    struct nvdimm_bus *nvdimm_bus)
+{
+	struct nd_mapping_desc mapping;
+	struct nd_region_desc ndr_desc;
+	struct nd_interleave_set *nd_set;
+	int nid = phys_to_target_node(res->start);
+
+	nd_set = kzalloc(sizeof(*nd_set), GFP_KERNEL);
+	if (!nd_set)
+		return -ENOMEM;
+
+	nd_set->cookie1 = get_random_u64();
+	nd_set->cookie2 = nd_set->cookie1;
+
+	memset(&mapping, 0, sizeof(mapping));
+	mapping.nvdimm = nvdimm;
+	mapping.start = 0;
+	mapping.size = resource_size(res) - LABEL_AREA_SIZE;
+
+	memset(&ndr_desc, 0, sizeof(ndr_desc));
+	ndr_desc.res = res;
+	ndr_desc.numa_node = numa_map_to_online_node(nid);
+	ndr_desc.target_node = nid;
+	ndr_desc.num_mappings = 1;
+	ndr_desc.mapping = &mapping;
+	ndr_desc.nd_set = nd_set;
+
+	if (!nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc))
+		goto err_free_nd_set;
+
+	return 0;
+
+err_free_nd_set:
+	kfree(nd_set);
+	return -ENXIO;
+}
+
+static int ramdax_register_dimm(struct resource *res, void *data)
+{
+	resource_size_t start = res->start;
+	resource_size_t size = resource_size(res);
+	unsigned long flags = 0, cmd_mask = 0;
+	struct nvdimm_bus *nvdimm_bus = data;
+	struct ramdax_dimm *dimm;
+	int err;
+
+	dimm = kzalloc(sizeof(*dimm), GFP_KERNEL);
+	if (!dimm)
+		return -ENOMEM;
+
+	dimm->label_area = memremap(start + size - LABEL_AREA_SIZE,
+				    LABEL_AREA_SIZE, MEMREMAP_WB);
+	if (!dimm->label_area)
+		goto err_free_dimm;
+
+	set_bit(NDD_LABELING, &flags);
+	set_bit(NDD_REGISTER_SYNC, &flags);
+	set_bit(ND_CMD_GET_CONFIG_SIZE, &cmd_mask);
+	set_bit(ND_CMD_GET_CONFIG_DATA, &cmd_mask);
+	set_bit(ND_CMD_SET_CONFIG_DATA, &cmd_mask);
+	dimm->nvdimm = nvdimm_create(nvdimm_bus, dimm,
+				     /* dimm_attribute_groups */ NULL,
+				     flags, cmd_mask, 0, NULL);
+	if (!dimm->nvdimm) {
+		err = -ENOMEM;
+		goto err_unmap_label;
+	}
+
+	err = ramdax_register_region(res, dimm->nvdimm, nvdimm_bus);
+	if (err)
+		goto err_remove_nvdimm;
+
+	return 0;
+
+err_remove_nvdimm:
+	nvdimm_delete(dimm->nvdimm);
+err_unmap_label:
+	memunmap(dimm->label_area);
+err_free_dimm:
+	kfree(dimm);
+	return err;
+}
+
+static int ramdax_get_config_size(struct nvdimm *nvdimm, int buf_len,
+				    struct nd_cmd_get_config_size *cmd)
+{
+	if (sizeof(*cmd) > buf_len)
+		return -EINVAL;
+
+	*cmd = (struct nd_cmd_get_config_size){
+		.status = 0,
+		.config_size = LABEL_AREA_SIZE,
+		.max_xfer = 8,
+	};
+
+	return 0;
+}
+
+static int ramdax_get_config_data(struct nvdimm *nvdimm, int buf_len,
+				    struct nd_cmd_get_config_data_hdr *cmd)
+{
+	struct ramdax_dimm *dimm = nvdimm_provider_data(nvdimm);
+
+	if (sizeof(*cmd) > buf_len)
+		return -EINVAL;
+	if (struct_size(cmd, out_buf, cmd->in_length) > buf_len)
+		return -EINVAL;
+	if (cmd->in_offset + cmd->in_length > LABEL_AREA_SIZE)
+		return -EINVAL;
+
+	memcpy(cmd->out_buf, dimm->label_area + cmd->in_offset, buf_len);
+
+	return 0;
+}
+
+static int ramdax_set_config_data(struct nvdimm *nvdimm, int buf_len,
+				    struct nd_cmd_set_config_hdr *cmd)
+{
+	struct ramdax_dimm *dimm = nvdimm_provider_data(nvdimm);
+
+	if (sizeof(*cmd) > buf_len)
+		return -EINVAL;
+	if (struct_size(cmd, in_buf, cmd->in_length) > buf_len)
+		return -EINVAL;
+	if (cmd->in_offset + cmd->in_length > LABEL_AREA_SIZE)
+		return -EINVAL;
+
+	memcpy(dimm->label_area + cmd->in_offset, cmd->in_buf, buf_len);
+
+	return 0;
+}
+
+static int ramdax_nvdimm_ctl(struct nvdimm *nvdimm, unsigned int cmd,
+			       void *buf, unsigned int buf_len)
+{
+	unsigned long cmd_mask = nvdimm_cmd_mask(nvdimm);
+
+	if (!test_bit(cmd, &cmd_mask))
+		return -ENOTTY;
+
+	switch (cmd) {
+	case ND_CMD_GET_CONFIG_SIZE:
+		return ramdax_get_config_size(nvdimm, buf_len, buf);
+	case ND_CMD_GET_CONFIG_DATA:
+		return ramdax_get_config_data(nvdimm, buf_len, buf);
+	case ND_CMD_SET_CONFIG_DATA:
+		return ramdax_set_config_data(nvdimm, buf_len, buf);
+	default:
+		return -ENOTTY;
+	}
+}
+
+static int ramdax_ctl(struct nvdimm_bus_descriptor *nd_desc,
+			 struct nvdimm *nvdimm, unsigned int cmd, void *buf,
+			 unsigned int buf_len, int *cmd_rc)
+{
+	/*
+	 * No firmware response to translate, let the transport error
+	 * code take precedence.
+	 */
+	*cmd_rc = 0;
+
+	if (!nvdimm)
+		return -ENOTTY;
+	return ramdax_nvdimm_ctl(nvdimm, cmd, buf, buf_len);
+}
+
+static int ramdax_probe_of(struct platform_device *pdev,
+			     struct nvdimm_bus *bus, struct device_node *np)
+{
+	int err;
+
+	for (int i = 0; i < pdev->num_resources; i++) {
+		err = ramdax_register_dimm(&pdev->resource[i], bus);
+		if (err)
+			goto err_unregister;
+	}
+
+	return 0;
+
+err_unregister:
+	/*
+	 * FIXME: should we unregister the dimms that were registered
+	 * successfully
+	 */
+	return err;
+}
+
+static int ramdax_probe(struct platform_device *pdev)
+{
+	static struct nvdimm_bus_descriptor nd_desc;
+	struct device *dev = &pdev->dev;
+	struct nvdimm_bus *nvdimm_bus;
+	struct device_node *np;
+	int rc = -ENXIO;
+
+	nd_desc.provider_name = "ramdax";
+	nd_desc.module = THIS_MODULE;
+	nd_desc.ndctl = ramdax_ctl;
+	nvdimm_bus = nvdimm_bus_register(dev, &nd_desc);
+	if (!nvdimm_bus)
+		goto err;
+
+	np = dev_of_node(&pdev->dev);
+	if (np)
+		rc = ramdax_probe_of(pdev, nvdimm_bus, np);
+	else
+		rc = walk_iomem_res_desc(IORES_DESC_PERSISTENT_MEMORY_LEGACY,
+					 IORESOURCE_MEM, 0, -1, nvdimm_bus,
+					 ramdax_register_dimm);
+	if (rc)
+		goto err;
+
+	platform_set_drvdata(pdev, nvdimm_bus);
+
+	return 0;
+err:
+	nvdimm_bus_unregister(nvdimm_bus);
+	return rc;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id ramdax_of_matches[] = {
+	{ .compatible = "pmem-region", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ramdax_of_matches);
+#endif
+
+static struct platform_driver ramdax_driver = {
+	.probe = ramdax_probe,
+	.remove = ramdax_remove,
+	.driver = {
+		.name = "e820_pmem",
+		.of_match_table = of_match_ptr(ramdax_of_matches),
+	},
+};
+
+module_platform_driver(ramdax_driver);
+
+MODULE_DESCRIPTION("NVDIMM support for e820 type-12 memory and OF pmem-region");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Microsoft Corporation");
author	Mike Rapoport (Microsoft) <rppt@kernel.org>	2025-05-11 12:51:14 +0300
committer	Mike Rapoport (Microsoft) <rppt@kernel.org>	2025-05-14 18:10:19 +0300
commit	0b81d6e851e5acf76aba4697db1281798bedbec8 (patch)
tree	74da229baedba3c4bde0d1f5446b2e9d20b60fd3
parent	92a09c47464d040866cf2b4cd052bc60555185fb (diff)
download	linux-ramdax.tar.gz