On Wed, 12 May 2021 at 22:11, Eric Biggers [off-list ref] wrote:

On Wed, May 12, 2021 at 08:44:32PM +0200, Ard Biesheuvel wrote:

quoted

This is a follow-up to [0], but given that the arm64 architectural
pieces have been merged for arm64, the only remaining changes are crypto
specific. Therefore, the audience has been reduced to those people who
are likely to care about these specifics.

Patch #1 addresses an issue in the skcipher walker which doesn't handle
zero sized AEAD inputs entirely consistently, which is uncovered by the
change in patch #7.

Patches #2 and #3 add some sanity checks to the public AEAD and skcipher
APIs to limit their availibility to either task or softirq context
(which is the only way in which they are currently being used). Adding
this restriction permits the arm64 crypto code to get rid of all scalar
fallbacks, given that on this architecture, softirqs are no longer
served while the SIMD unit is being used in kernel mode, which means
that the scalar fallbacks are never needed. These are removed in the
remaining 4 patches.

[0] https://lore.kernel.org/linux-arm-kernel/20210302090118.30666-1-ardb@kernel.org/ (local)

Did you check whether any updates to the self-tests in testmgr.c are warranted?
Specifically, is disabling the use of SIMD for testing still something that
makes sense?

The situation is not ideal, but I am not sure what we can do about
this: the scalar fallbacks are gone, which means that the SIMD unit
will be used in the test even if testmgr attempts to disable it. But
keeping the scalar fallbacks just for the test suite makes no sense
either. So I don't think we should change anything, other than perhaps
document this somewhere (any suggestions on a place to put that)

Note that the library routines, as well as shashes (which are
sometimes exposed via library routines, e.g., CRC-T10DIF and CRC-32,
and maybe others) are different, which is why their scalar fallbacks
are retained. There, we need the testmgr to override SIMD availability
to ensure that combinations of the SIMD and scalar code are tested.

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