On Wed, Feb 10, 2021 at 12:59:59PM -0700, Jens Axboe wrote: > On 2/10/21 12:33 PM, Mike Snitzer wrote: > > On Mon, Feb 01 2021 at 12:10am -0500, > > Satya Tangirala <satyat@xxxxxxxxxx> wrote: > > > >> This patch series adds support for inline encryption to the device mapper. > >> > >> Patch 1 introduces the "passthrough" keyslot manager. > >> > >> The regular keyslot manager is designed for inline encryption hardware that > >> have only a small fixed number of keyslots. A DM device itself does not > >> actually have only a small fixed number of keyslots - it doesn't actually > >> have any keyslots in the first place, and programming an encryption context > >> into a DM device doesn't make much semantic sense. It is possible for a DM > >> device to set up a keyslot manager with some "sufficiently large" number of > >> keyslots in its request queue, so that upper layers can use the inline > >> encryption capabilities of the DM device's underlying devices, but the > >> memory being allocated for the DM device's keyslots is a waste since they > >> won't actually be used by the DM device. > >> > >> The passthrough keyslot manager solves this issue - when the block layer > >> sees that a request queue has a passthrough keyslot manager, it doesn't > >> attempt to program any encryption context into the keyslot manager. The > >> passthrough keyslot manager only allows the device to expose its inline > >> encryption capabilities, and a way for upper layers to evict keys if > >> necessary. > >> > >> There also exist inline encryption hardware that can handle encryption > >> contexts directly, and allow users to pass them a data request along with > >> the encryption context (as opposed to inline encryption hardware that > >> require users to first program a keyslot with an encryption context, and > >> then require the users to pass the keyslot index with the data request). > >> Such devices can also make use of the passthrough keyslot manager. > >> > >> Patch 2 introduces some keyslot manager functions useful for the device > >> mapper. > >> > >> Patch 3 introduces the changes for inline encryption support for the device > >> mapper. A DM device only exposes the intersection of the crypto > >> capabilities of its underlying devices. This is so that in case a bio with > >> an encryption context is eventually mapped to an underlying device that > >> doesn't support that encryption context, the blk-crypto-fallback's cipher > >> tfms are allocated ahead of time by the call to blk_crypto_start_using_key. > >> > >> Each DM target can now also specify the "DM_TARGET_PASSES_CRYPTO" flag in > >> the target type features to opt-in to supporting passing through the > >> underlying inline encryption capabilities. This flag is needed because it > >> doesn't make much semantic sense for certain targets like dm-crypt to > >> expose the underlying inline encryption capabilities to the upper layers. > >> Again, the DM exposes inline encryption capabilities of the underlying > >> devices only if all of them opt-in to passing through inline encryption > >> support. > >> > >> A keyslot manager is created for a table when it is loaded. However, the > >> mapped device's exposed capabilities *only* updated once the table is > >> swapped in (until the new table is swapped in, the mapped device continues > >> to expose the old table's crypto capabilities). > >> > >> This patch only allows the keyslot manager's capabilities to *expand* > >> because of table changes. Any attempt to load a new table that doesn't > >> support a crypto capability that the old table did is rejected. > >> > >> This patch also only exposes the intersection of the underlying device's > >> capabilities, which has the effect of causing en/decryption of a bio to > >> fall back to the kernel crypto API (if the fallback is enabled) whenever > >> any of the underlying devices doesn't support the encryption context of the > >> bio - it might be possible to make the bio only fall back to the kernel > >> crypto API if the bio's target underlying device doesn't support the bio's > >> encryption context, but the use case may be uncommon enough in the first > >> place not to warrant worrying about it right now. > >> > >> Patch 4 makes DM evict a key from all its underlying devices when asked to > >> evict a key. > >> > >> Patch 5 makes some DM targets opt-in to passing through inline encryption > >> support. It does not (yet) try to enable this option with dm-raid, since > >> users can "hot add" disks to a raid device, which makes this not completely > >> straightforward (we'll need to ensure that any "hot added" disks must have > >> a superset of the inline encryption capabilities of the rest of the disks > >> in the raid device, due to the way Patch 2 of this series works). > >> > >> Changes v3 => v4: > >> - Allocate the memory for the ksm of the mapped device in > >> dm_table_complete(), and install the ksm in the md queue in __bind() > >> (as suggested by Mike). Also drop patch 5 from v3 since it's no longer > >> needed. > >> - Some cleanups > >> > >> Changes v2 => v3: > >> - Split up the main DM patch into 4 separate patches > >> - Removed the priv variable added to struct keyslot manager in v2 > >> - Use a flag in target type features for opting-in to inline encryption > >> support, instead of using "may_passthrough_inline_crypto" > >> - cleanups, improve docs and restructure code > >> > >> Changes v1 => v2: > >> - Introduce private field to struct blk_keyslot_manager > >> - Allow the DM keyslot manager to expand its crypto capabilities if the > >> table is changed. > >> - Make DM reject table changes that would otherwise cause crypto > >> capabilities to be dropped. > >> - Allocate the DM device's keyslot manager only when at least one crypto > >> capability is supported (since a NULL value for q->ksm represents "no > >> crypto support" anyway). > >> - Remove the struct blk_keyslot_manager field from struct mapped_device. > >> This patch now relies on just directly setting up the keyslot manager in > >> the request queue, since each DM device is tied to only 1 queue. > >> > >> Satya Tangirala (5): > >> block: keyslot-manager: Introduce passthrough keyslot manager > >> block: keyslot-manager: Introduce functions for device mapper support > >> dm: add support for passing through inline crypto support > >> dm: support key eviction from keyslot managers of underlying devices > >> dm: set DM_TARGET_PASSES_CRYPTO feature for some targets > >> > >> block/blk-crypto.c | 1 + > >> block/keyslot-manager.c | 146 ++++++++++++++++++++++ > >> drivers/md/dm-core.h | 5 + > >> drivers/md/dm-flakey.c | 4 +- > >> drivers/md/dm-linear.c | 5 +- > >> drivers/md/dm-table.c | 210 ++++++++++++++++++++++++++++++++ > >> drivers/md/dm.c | 18 ++- > >> include/linux/device-mapper.h | 11 ++ > >> include/linux/keyslot-manager.h | 11 ++ > >> 9 files changed, 407 insertions(+), 4 deletions(-) > >> > >> -- > >> 2.30.0.365.g02bc693789-goog > >> > > > > This set looks good to me now. > > > > To avoid DM needing another rebase on block: Jens (and others), would > > you like to review patches 1 and 2 (and reply with your Reviewed-by) so > > I could pickup the DM required keyslot-manager changes along with > > patches 3-5? > > You can add my acked-by to 1+2 and queue it up. > I resent the series (as v5) while addressing the comments Eric had on Patch 3 (the changes were only to comments, so no functional changes). I also added the acked/reviewed-bys. > -- > Jens Axboe >
