device-dax: Add a driver for "hmem" devices

Platform firmware like EFI/ACPI may publish "hmem" platform devices.
Such a device is a performance differentiated memory range likely
reserved for an application specific use case. The driver gives access
to 100% of the capacity via a device-dax mmap instance by default.

However, if over-subscription and other kernel memory management is
desired the resulting dax device can be assigned to the core-mm via the
kmem driver.

This consumes "hmem" devices the producer of "hmem" devices is saved for
a follow-on patch so that it can reference the new CONFIG_DEV_DAX_HMEM
symbol to gate performing the enumeration work.

Reported-by: kbuild test robot <lkp@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index f33c73e..3b6c06f 100644 (file)
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -32,19 +32,36 @@ config DEV_DAX_PMEM
 
          Say M if unsure
 
 
          Say M if unsure
 

+config DEV_DAX_HMEM
+       tristate "HMEM DAX: direct access to 'specific purpose' memory"
+       depends on EFI_SOFT_RESERVE
+       default DEV_DAX
+       help
+         EFI 2.8 platforms, and others, may advertise 'specific purpose'
+         memory. For example, a high bandwidth memory pool. The
+         indication from platform firmware is meant to reserve the
+         memory from typical usage by default. This driver creates
+         device-dax instances for these memory ranges, and that also
+         enables the possibility to assign them to the DEV_DAX_KMEM
+         driver to override the reservation and add them to kernel
+         "System RAM" pool.
+
+         Say M if unsure.
+

 config DEV_DAX_KMEM
        tristate "KMEM DAX: volatile-use of persistent memory"
        default DEV_DAX
        depends on DEV_DAX
        depends on MEMORY_HOTPLUG # for add_memory() and friends
        help
 config DEV_DAX_KMEM
        tristate "KMEM DAX: volatile-use of persistent memory"
        default DEV_DAX
        depends on DEV_DAX
        depends on MEMORY_HOTPLUG # for add_memory() and friends
        help

-         Support access to persistent memory as if it were RAM.  This
-         allows easier use of persistent memory by unmodified
-         applications.
+         Support access to persistent, or other performance
+         differentiated memory as if it were System RAM. This allows
+         easier use of persistent memory by unmodified applications, or
+         adds core kernel memory services to heterogeneous memory types
+         (HMEM) marked "reserved" by platform firmware.

 
          To use this feature, a DAX device must be unbound from the
 
          To use this feature, a DAX device must be unbound from the

-         device_dax driver (PMEM DAX) and bound to this kmem driver
-         on each boot.
+         device_dax driver and bound to this kmem driver on each boot.

 
          Say N if unsure.
 
 
          Say N if unsure.
 

diff --git a/drivers/dax/Makefile b/drivers/dax/Makefile
index 81f7d54..80065b3 100644 (file)
--- a/drivers/dax/Makefile
+++ b/drivers/dax/Makefile
@@ -2,9 +2,11 @@
 obj-$(CONFIG_DAX) += dax.o
 obj-$(CONFIG_DEV_DAX) += device_dax.o
 obj-$(CONFIG_DEV_DAX_KMEM) += kmem.o
 obj-$(CONFIG_DAX) += dax.o
 obj-$(CONFIG_DEV_DAX) += device_dax.o
 obj-$(CONFIG_DEV_DAX_KMEM) += kmem.o

+obj-$(CONFIG_DEV_DAX_HMEM) += dax_hmem.o

 
 dax-y := super.o
 dax-y += bus.o
 device_dax-y := device.o
 
 dax-y := super.o
 dax-y += bus.o
 device_dax-y := device.o

+dax_hmem-y := hmem.o

 
 obj-y += pmem/
 
 obj-y += pmem/

diff --git a/drivers/dax/hmem.c b/drivers/dax/hmem.c
new file mode 100644 (file)
index 0000000..fe7214d
--- /dev/null
+++ b/drivers/dax/hmem.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/platform_device.h>
+#include <linux/memregion.h>
+#include <linux/module.h>
+#include <linux/pfn_t.h>
+#include "bus.h"
+
+static int dax_hmem_probe(struct platform_device *pdev)
+{
+       struct device *dev = &pdev->dev;
+       struct dev_pagemap pgmap = { };
+       struct dax_region *dax_region;
+       struct memregion_info *mri;
+       struct dev_dax *dev_dax;
+       struct resource *res;
+
+       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+       if (!res)
+               return -ENOMEM;
+
+       mri = dev->platform_data;
+       memcpy(&pgmap.res, res, sizeof(*res));
+
+       dax_region = alloc_dax_region(dev, pdev->id, res, mri->target_node,
+                       PMD_SIZE, PFN_DEV|PFN_MAP);
+       if (!dax_region)
+               return -ENOMEM;
+
+       dev_dax = devm_create_dev_dax(dax_region, 0, &pgmap);
+       if (IS_ERR(dev_dax))
+               return PTR_ERR(dev_dax);
+
+       /* child dev_dax instances now own the lifetime of the dax_region */
+       dax_region_put(dax_region);
+       return 0;
+}
+
+static int dax_hmem_remove(struct platform_device *pdev)
+{
+       /* devm handles teardown */
+       return 0;
+}
+
+static struct platform_driver dax_hmem_driver = {
+       .probe = dax_hmem_probe,
+       .remove = dax_hmem_remove,
+       .driver = {
+               .name = "hmem",
+       },
+};
+
+module_platform_driver(dax_hmem_driver);
+
+MODULE_ALIAS("platform:hmem*");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Intel Corporation");

diff --git a/include/linux/memregion.h b/include/linux/memregion.h
index 7de7c0a..e115952 100644 (file)
--- a/include/linux/memregion.h
+++ b/include/linux/memregion.h
@@ -4,6 +4,10 @@
 #include <linux/types.h>
 #include <linux/errno.h>
 
 #include <linux/types.h>
 #include <linux/errno.h>
 

+struct memregion_info {
+       int target_node;
+};
+

 #ifdef CONFIG_MEMREGION
 int memregion_alloc(gfp_t gfp);
 void memregion_free(int id);
 #ifdef CONFIG_MEMREGION
 int memregion_alloc(gfp_t gfp);
 void memregion_free(int id);