[PATCH v2 3/3] dm: add documentation for dm-inlinecrypt target

Linlin Zhang
2026-04-10T13:40:43Z

This adds the admin-guide documentation for dm-inlinecrypt.

dm-inlinecrypt.rst is the guide to using dm-inlinecrypt.

Signed-off-by: Linlin Zhang <linlin.zhang@oss.qualcomm.com>
---
.../device-mapper/dm-inlinecrypt.rst | 122 ++++++++++++++++++
1 file changed, 122 insertions(+)
create mode 100644 Documentation/admin-guide/device-mapper/dm-inlinecrypt.rst

diff --git a/Documentation/admin-guide/device-mapper/dm-inlinecrypt.rst b/Documentation/admin-guide/device-mapper/dm-inlinecrypt.rst
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+========
+dm-inlinecrypt
+========
+
+Device-Mapper's "inlinecrypt" target provides transparent encryption of block devices
+using the inline encryption hardware.
+
+For a more detailed description of inline encryption, see:
+https://docs.kernel.org/block/inline-encryption.html
+
+Parameters::
+
+ <cipher> <key> <iv_offset> <device path> \
+ <offset> [<#opt_params> <opt_params>]
+
+<cipher>
+ Encryption cipher type.
+
+ The cipher specifications format is::
+
+ cipher
+
+ Examples::
+
+ aes-xts-plain64
+
+ The cipher type is correspond one-to-one with encryption modes. For
+ instance, the corresponding crypto mode of aes-xts-plain64 is
+ BLK_ENCRYPTION_MODE_AES_256_XTS.
+
+<key>
+ Key used for encryption. It is encoded either as a hexadecimal number
+ or it can be passed as <key_string> prefixed with single colon
+ character (':') for keys residing in kernel keyring service.
+ You can only use key sizes that are valid for the selected cipher.
+ Note that the size in bytes of a valid key must be in bellow range.
+
+ [BLK_CRYPTO_KEY_TYPE_RAW, BLK_CRYPTO_KEY_TYPE_HW_WRAPPED]
+
+<key_string>
+ The kernel keyring key is identified by string in following format:
+ <key_size>:<key_type>:<key_description>.
+
+<key_size>
+ The encryption key size in bytes. The kernel key payload size must match
+ the value passed in <key_size>.
+
+<key_type>
+ Either 'logon', or 'trusted' kernel key type.
+
+<key_description>
+ The kernel keyring key description inlinecrypt target should look for
+ when loading key of <key_type>.
+
+<iv_offset>
+ The IV offset is a sector count that is added to the sector number
+ before creating the IV.
+
+<device path>
+ This is the device that is going to be used as backend and contains the
+ encrypted data. You can specify it as a path like /dev/xxx or a device
+ number <major>:<minor>.
+
+<offset>
+ Starting sector within the device where the encrypted data begins.
+
+<#opt_params>
+ Number of optional parameters. If there are no optional parameters,
+ the optional parameters section can be skipped or #opt_params can be zero.
+ Otherwise #opt_params is the number of following arguments.
+
+ Example of optional parameters section:
+ allow_discards sector_size:4096 iv_large_sectors
+
+allow_discards
+ Block discard requests (a.k.a. TRIM) are passed through the inlinecrypt
+ device. The default is to ignore discard requests.
+
+ WARNING: Assess the specific security risks carefully before enabling this
+ option. For example, allowing discards on encrypted devices may lead to
+ the leak of information about the ciphertext device (filesystem type,
+ used space etc.) if the discarded blocks can be located easily on the
+ device later.
+
+sector_size:<bytes>
+ Use <bytes> as the encryption unit instead of 512 bytes sectors.
+ This option can be in range 512 - 4096 bytes and must be power of two.
+ Virtual device will announce this size as a minimal IO and logical sector.
+
+iv_large_sectors
+ IV generators will use sector number counted in <sector_size> units
+ instead of default 512 bytes sectors.
+
+ For example, if <sector_size> is 4096 bytes, plain64 IV for the second
+ sector will be 8 (without flag) and 1 if iv_large_sectors is present.
+ The <iv_offset> must be multiple of <sector_size> (in 512 bytes units)
+ if this flag is specified.
+
+Example scripts
+===============
+LUKS (Linux Unified Key Setup) is now the preferred way to set up disk
+encryption with dm-inlinecrypt using the 'cryptsetup' utility, see
+https://gitlab.com/cryptsetup/cryptsetup
+
+::
+
+ #!/bin/sh
+ # Create a inlinecrypt device using dmsetup
+ dmsetup create inlinecrypt1 --table "0 `blockdev --getsz $1` inlinecrypt aes-xts-plain64 babebabebabebabebabebabebabebabebabebabebabebabebabebabebabebabe 0 $1 0"
+
+::
+
+ #!/bin/sh
+ # Create a inlinecrypt device using dmsetup when encryption key is stored in keyring service
+ dmsetup create inlinecrypt2 --table "0 `blockdev --getsz $1` inlinecrypt aes-xts-plain64 :64:logon:fde:dminlinecrypt_test_key 0 $1 0"
+
+::
+
+ #!/bin/sh
+ # Create a inlinecrypt device using cryptsetup and LUKS header with default cipher
+ cryptsetup luksFormat $1
+ cryptsetup luksOpen $1 inlinecrypt1
--
2.34.1