[Bug 252981] panic with ZFS encryption and QAT: VERIFY3(0 == spa_do_crypt_bad(...

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=252981

--- Comment #2 from Mark Johnston <markj at FreeBSD.org> ---
(In reply to Mark Johnston from comment #1)
With this fixed I hit the same panic as in the PR title.  QAT has some weird
constraints around the AAD length for GCM/CCM; in particular, it must be no
more than 240 bytes in length.  This is implemented in the Intel and DPDK QAT
drivers as well as ours.

ZFS is submitting GCM encryption requests with a large AAD (I think when
encrypting a block of dnodes?) and hitting the check in qat_process(), and it
can't tolerate the error.  Weirdly, the ZFS QAT stub for Linux has no check for
this case, but it also only uses QAT for data blocks, which I believe have no
AAD.  See qat_crypt_use_accel().

So for now we should at least change ZFS to not use hardware crypto since it
doesn't work and clearly hasn't been tested (see comment 1).  I'm not sure how
hard it would be to permit the use of hardware crypto only for data blocks (and
not for the ZIL and dnode blocks, which requires support for large AAD buffers.

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