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>
This commit is contained in:
Dan Williams 2019-11-06 17:43:43 -08:00 committed by Rafael J. Wysocki
parent 460370ab20
commit a6c7f4c6ae
4 changed files with 84 additions and 5 deletions

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@ -32,19 +32,36 @@ config DEV_DAX_PMEM
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
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
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.

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@ -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_DEV_DAX_HMEM) += dax_hmem.o
dax-y := super.o
dax-y += bus.o
device_dax-y := device.o
dax_hmem-y := hmem.o
obj-y += pmem/

56
drivers/dax/hmem.c Normal file
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@ -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");

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@ -4,6 +4,10 @@
#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);