Commit 9f960da7 authored by Pavel Tatashin's avatar Pavel Tatashin Committed by Linus Torvalds

device-dax: "Hotremove" persistent memory that is used like normal RAM

It is now allowed to use persistent memory like a regular RAM, but
currently there is no way to remove this memory until machine is
rebooted.

This work expands the functionality to also allows hotremoving
previously hotplugged persistent memory, and recover the device for use
for other purposes.

To hotremove persistent memory, the management software must first
offline all memory blocks of dax region, and than unbind it from
device-dax/kmem driver.  So, operations should look like this:

  echo offline > /sys/devices/system/memory/memoryN/state
  ...
  echo dax0.0 > /sys/bus/dax/drivers/kmem/unbind

Note: if unbind is done without offlining memory beforehand, it won't be
possible to do dax0.0 hotremove, and dax's memory is going to be part of
System RAM until reboot.

Link: http://lkml.kernel.org/r/20190517215438.6487-4-pasha.tatashin@soleen.comSigned-off-by: default avatarPavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent eca499ab
...@@ -43,6 +43,7 @@ struct dax_region { ...@@ -43,6 +43,7 @@ struct dax_region {
* @target_node: effective numa node if dev_dax memory range is onlined * @target_node: effective numa node if dev_dax memory range is onlined
* @dev - device core * @dev - device core
* @pgmap - pgmap for memmap setup / lifetime (driver owned) * @pgmap - pgmap for memmap setup / lifetime (driver owned)
* @dax_mem_res: physical address range of hotadded DAX memory
*/ */
struct dev_dax { struct dev_dax {
struct dax_region *region; struct dax_region *region;
...@@ -50,6 +51,7 @@ struct dev_dax { ...@@ -50,6 +51,7 @@ struct dev_dax {
int target_node; int target_node;
struct device dev; struct device dev;
struct dev_pagemap pgmap; struct dev_pagemap pgmap;
struct resource *dax_kmem_res;
}; };
static inline struct dev_dax *to_dev_dax(struct device *dev) static inline struct dev_dax *to_dev_dax(struct device *dev)
......
...@@ -71,21 +71,54 @@ int dev_dax_kmem_probe(struct device *dev) ...@@ -71,21 +71,54 @@ int dev_dax_kmem_probe(struct device *dev)
kfree(new_res); kfree(new_res);
return rc; return rc;
} }
dev_dax->dax_kmem_res = new_res;
return 0; return 0;
} }
#ifdef CONFIG_MEMORY_HOTREMOVE
static int dev_dax_kmem_remove(struct device *dev)
{
struct dev_dax *dev_dax = to_dev_dax(dev);
struct resource *res = dev_dax->dax_kmem_res;
resource_size_t kmem_start = res->start;
resource_size_t kmem_size = resource_size(res);
int rc;
/*
* We have one shot for removing memory, if some memory blocks were not
* offline prior to calling this function remove_memory() will fail, and
* there is no way to hotremove this memory until reboot because device
* unbind will succeed even if we return failure.
*/
rc = remove_memory(dev_dax->target_node, kmem_start, kmem_size);
if (rc) {
dev_err(dev,
"DAX region %pR cannot be hotremoved until the next reboot\n",
res);
return rc;
}
/* Release and free dax resources */
release_resource(res);
kfree(res);
dev_dax->dax_kmem_res = NULL;
return 0;
}
#else
static int dev_dax_kmem_remove(struct device *dev) static int dev_dax_kmem_remove(struct device *dev)
{ {
/* /*
* Purposely leak the request_mem_region() for the device-dax * Without hotremove purposely leak the request_mem_region() for the
* range and return '0' to ->remove() attempts. The removal of * device-dax range and return '0' to ->remove() attempts. The removal
* the device from the driver always succeeds, but the region * of the device from the driver always succeeds, but the region is
* is permanently pinned as reserved by the unreleased * permanently pinned as reserved by the unreleased
* request_mem_region(). * request_mem_region().
*/ */
return 0; return 0;
} }
#endif /* CONFIG_MEMORY_HOTREMOVE */
static struct dax_device_driver device_dax_kmem_driver = { static struct dax_device_driver device_dax_kmem_driver = {
.drv = { .drv = {
......
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