daxctl-create-device - Man Page

Create a devdax device

Synopsis

daxctl create-device [<options>]

Examples

.ft C
# daxctl create-device -s 4G
[
  {
    "chardev":"dax0.1",
    "size":4294967296,
    "target_node":0,
    "mode":"devdax"
  }
]
.ft
.ft C
# daxctl create-device -u
[
  {
    "chardev":"dax0.1",
    "size":"15.63 GiB (16.78 GB)",
    "target_node":0,
    "mode":"devdax"
  },
  {
    "chardev":"dax1.1",
    "size":"15.63 GiB (16.78 GB)",
    "target_node":1,
    "mode":"devdax"
  }
]
.ft
.ft C
# daxctl create-device -r 0 -u
{
  "chardev":"dax0.1",
  "size":"15.63 GiB (16.78 GB)",
  "target_node":0,
  "mode":"devdax"
}
.ft

Description

Creates dax device in devdax mode in dynamic regions. The resultant can also be convereted to the system-ram mode which arranges for the dax range to be hot-plugged into the system as regular memory.

daxctl create-device expects that the BIOS or kernel defines a range in the EFI memory map with EFI_MEMORY_SP. The resultant ranges mean that it’s 100% capacity is reserved for applications.

Options

-r,  --region=

Restrict the operation to devices belonging to the specified region(s). A device-dax region is a contiguous range of memory that hosts one or more /dev/daxX.Y devices, where X is the region id and Y is the device instance id.

-s,  --size=

For regions that support dax device cretion, set the device size in bytes. Otherwise it defaults to the maximum size specified by region. This option supports the suffixes "k" or "K" for KiB, "m" or "M" for MiB, "g" or "G" for GiB and "t" or "T" for TiB.

The size must be a multiple of the region alignment.
-a,  --align

Applications that want to establish dax memory mappings with page table entries greater than system base page size (4K on x86) need a device that is sufficiently aligned. This defaults to 2M. Note that "devdax" mode enforces all mappings to be aligned to this value, i.e. it fails unaligned mapping attempts.

--input

Applications that want to select ranges assigned to a device-dax instance, or wanting to establish previously created devices, can pass an input JSON file. The file option lets a user pass a JSON object similar to the one listed with "daxctl list".

The device name is not re-created, but if a "chardev" is passed in
the JSON file, it will use that to get the region id.
Note that the JSON content in the file cannot be an array of
JSON objects but rather a single JSON object i.e. without the
array enclosing brackets.
-u,  --human

By default the command will output machine-friendly raw-integer data. Instead, with this flag, numbers representing storage size will be formatted as human readable strings with units, other fields are converted to hexadecimal strings.

-v,  --verbose

Emit more debug messages

See Also

daxctl-list(1),daxctl-reconfigure-device[1],daxctl-destroy-device[1]

Info

01/26/2021 daxctl 71.1 daxctl Manual