Re: [RFC PATCH] arm64: add support for AES in CCM mode using Crypto Extensions

On Tue, Feb 11, 2014 at 09:21:45AM +0100, Ard Biesheuvel wrote:

This adds support for a synchronous implementation of AES in CCM mode
using ARMv8 Crypto Extensions, using NEON registers q0 - q5.

Signed-off-by: Ard Biesheuvel <redacted>
---
Hi all,

I am posting this for review/RFC. The main topic for feedback is the way
I have used an inner blkcipher instance to process the encrypted + authenticated
data.

The point of having a dedicated module for synchronous ccm(aes) is the fact that
mac80211 uses it for WPA2 CCMP en-/decryption, where it runs entirely in soft
IRQ context. In this case, the performance improvement offered by dedicated AES
instructions is likely wasted on stacking and unstacking the NEON register file,
as the generic CCM operates on a single AES block at a time.

Instead, this implementation interleaves the CTR and CBC modes at the round
level, eliminating 50% of both the input and round key loads and (hopefully)
eliminating pipeline stalls by operating on two AES blocks at a time.

Tested with tcrypt, no performance numbers yet.

I think your idea definitely make sense, since we do the same
thing in aesni-intel.

It'll be interesting to see some numbers, especially if we could
compare this against the generic version that we talked about
earlier.

Thanks,
-- 
Email: Herbert Xu [off-list ref]
Home Page: http://gondor.apana.org.au/~herbert/
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