Re: [RFC PATCH] dm-inlinecrypt: add target for inline block device encryption

[Eric Biggers <ebiggers@kernel.org>]

On Thu, Oct 03, 2024 at 10:44:07PM -0700, Christoph Hellwig wrote:
> On Thu, Oct 03, 2024 at 05:41:52PM -0700, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@google.com>
> > 
> > Add a new device-mapper target "dm-inlinecrypt" that is similar to
> > dm-crypt but uses the blk-crypto API instead of the regular crypto API.
> > This allows it to take advantage of inline encryption hardware such as
> > that commonly built into UFS host controllers.
> > 
> > The table syntax matches dm-crypt's, but for now only a stripped-down
> > set of parameters is supported.  For example, for now AES-256-XTS is the
> > only supported cipher.
> 
> Maybe I'm stepping into a mine-field here, but if this simply uses
> blk-crypto to accellerate a subset of dm-crypt, why isn't dm-crypt
> simply enhanced to use blk-crypto when available?
> compatible,
> 

Milan Broz (cryptsetup maintainer) has said that he prefers a separate dm
target.  See
https://lore.kernel.org/dm-devel/9ef95bbc-4eee-4c00-f199-0daa3cdd03ed@gmail.com/

That was a couple years ago though, and this discussion seems to have gone
around in a circle.  Maybe things have changed.

A dm-crypt extension sounds fine to me too, though keep in mind there will
eventually be inline crypto exclusive features such as hardware-wrapped keys.

- Eric