On Fri, 15 Jan 2021 at 18:56, Eric Biggers [off-list ref] wrote:

On Fri, Jan 15, 2021 at 10:22:03AM +0100, Ulf Hansson wrote:

quoted

On Mon, 4 Jan 2021 at 19:48, Eric Biggers [off-list ref] wrote:

quoted

From: Eric Biggers <redacted>

In preparation for adding CQHCI crypto engine (inline encryption)
support, add the code required to make mmc_core and mmc_block aware of
inline encryption.  Specifically:

- Add a capability flag MMC_CAP2_CRYPTO to struct mmc_host.  Drivers
  will set this if the host and driver support inline encryption.

- Embed a blk_keyslot_manager in struct mmc_host.  Drivers will
  initialize this if the host and driver support inline encryption.
  mmc_block registers this keyslot manager with the request_queue of any
  MMC card attached to the host.  mmc_core destroys this keyslot manager
  when freeing the mmc_host.

- Make mmc_block copy the crypto keyslot and crypto data unit number
  from struct request to struct mmc_request, so that drivers will have
  access to them.

- If the MMC host is reset, reprogram all the keyslots to ensure that
  the software state stays in sync with the hardware state.

Co-developed-by: Satya Tangirala <redacted>
Signed-off-by: Satya Tangirala <redacted>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Satya Tangirala <redacted>
Reviewed-and-tested-by: Peng Zhou [off-list ref]
Signed-off-by: Eric Biggers <redacted>

Eric, again, my apologies for the delay. Overall, I think this looks good.

My only hesitation to merge this as is, is that I want to make sure
you have thought of the life cycle issues for the struct
blk_keyslot_manager ksm. It's being used both from the mmc core/block
device driver and the mmc host driver. I am looking at this right now
and will get back to you very soon, if I find some issues with it.

If you have some time, feel free to elaborate around how this is
intended to work.

Kind regards
Uffe

The blk_keyslot_manager is initialized early on when the other host structures
(struct mmc_host, struct cqhci_host, struct sdhci_host, struct sdhci_msm_host)
are initialized, prior to mmc_add_host().

It is destroyed when the struct mmc_host is freed by mmc_free_host().

So it should just work; it's the same lifecycle as the existing host structures.
Is there something you think I'm overlooking?

I think so, but let me elaborate a bit.

As I understand it, to initialize the data structures, blk_ksm_init()
is getting called and via cqhci_init().

To hook up the block request queue, blk_ksm_register() is called via
mmc_setup_queue(), which means this happens when the mmc block device
driver is probed.

To free up the data structures, blk_ksm_destroy() is called from
mmc_free_host().

To me, this can be made more consistent. For example, it looks like
blk_ksm_destroy() could be called, even if blk_ksm_init() hasn't been
called (depending on the probe error path of the mmc host).

There are a couple of options to better deal with this.
1) Extend the blk_ksm interface with a devm_blk_ksm_init() function
(thus let it deal with lifecycle problems for us) and simply drop the
call to blk_ksm_destroy().
2) Extend the cqhci interface with a cleanup function (perhaps
"cqhci_deinit") and let it call blk_ksm_destroy().
3) Convert to let blk_ksm_init() to be called from mmc_add_host() and
blk_ksm_destroy() from mmc_remove_host().

Moreover, even if there seems to be no real need to call
blk_ksm_unregister() for the mmc block device driver, perhaps we
should still do it to be consistent with blk_ksm_register()?

Then a final concern. It looks like the mmc core relies on checking
"host->caps2 & MMC_CAP2_CRYPTO", when it calls blk_ksm_register() and
blk_ksm_reprogram_all_keys(), for example. Normally, host->caps2 bits
are considered as static configurations and set during the host driver
probe path, which may not be a good match for this case. Instead, it
seems like we should set a new separate flag, to indicate for the mmc
core that blk_ksm_init has been enabled. Otherwise it looks like we
could end up calling blk_ksm_reprogram_all_keys(), even if
blk_ksm_init() hasn't been called.

Kind regards
Uffe