Re: [PATCH v2 00/21] crypto: x86 - remove glue helper module

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On Tue, Jan 05, 2021 at 05:47:48PM +0100, Ard Biesheuvel wrote:
> NOTE: this is a follow-up to '[RFC PATCH 00/10] crypto: x86 - remove XTS and
> CTR glue helper code' [0].
> 
> After applying my performance fixes for AES-NI in XTS mode, the only
> remaining users of the x86 glue helper module are the niche algorithms
> camellia, cast5/6, serpent and twofish.
> 
> It is not clear from the history why all these different versions of these
> algorithms in XTS and CTR modes were added in the first place: the only
> in-kernel references that seem to exist are to cbc(serpent), cbc(camellia)
> and cbc(twofish) in the IPsec stack. The XTS spec only mentions AES, and
> CTR modes don't seem to be widely used either.
> 
> Since the glue helper code relies heavily on indirect calls for small chunks
> of in/output, it needs some work to recover from the performance hit caused
> by the retpoline changes. However, it makes sense to only expend the effort
> for algorithms that are being used in the first place, and this does not
> seem to be the case for XTS and CTR.
> 
> CTR mode can simply be removed: it is not used in the kernel, and it is
> highly unlikely that it is being relied upon via algif_skcipher. And even
> if it was, the generic CTR mode driver can still provide the CTR transforms
> if necessary. While at it, accelerated implementations of DES and Blowfish
> in CTR mode are removed as well, for the same reasons.
> 
> XTS mode may actually be in use by dm-crypt users *, so we cannot simply drop
> this code entirely. However, as it turns out, the XTS template wrapped
> around the ECB mode skciphers perform roughly on par, and so there is no
> need to retain all the complicated XTS helper logic. Users of dm-crypt that
> are relying on xts(camellia) or xts(serpent) in the field should not be
> impacted by these changes at all.
> 
> ECB and CBC are retained, but the glue helper indirection is replaced with
> a set of preprocessor macros which can be used to instantiate the same logic
> flow, but without relying on indirect calls into the glue helper module.
> Please refer to patch #14 for more background.
> 
> * Milan points out that Serpent, Camellia and Twofish in XTS mode are used
>   by TrueCrypt/Veracrypt, which means that dm-crypt should retain support
>   for these algorithms as well.
> 
> [0] https://lore.kernel.org/linux-crypto/20201223223841.11311-1-ardb@xxxxxxxxxx/
> 
> Changes since v1:
> - avoid unnecessary memcpy()s in the new CBC decryption helper macro
> - avoid unnecessary memcpy() in camellia_decrypt_cbc_2way()
> - add Eric's ack
> 
> Changes since RFC:
> - add Eric's ack to the initial XTS and CTR patches
> - add patches to convert ECB and CBC modes
> - add patches to remove DES and Blowfish in CTR mode
> 
> Cc: Megha Dey <megha.dey@xxxxxxxxx>
> Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cc: Milan Broz <gmazyland@xxxxxxxxx>
> Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
> 
> Ard Biesheuvel (21):
>   crypto: x86/camellia - switch to XTS template
>   crypto: x86/cast6 - switch to XTS template
>   crypto: x86/serpent- switch to XTS template
>   crypto: x86/twofish - switch to XTS template
>   crypto: x86/glue-helper - drop XTS helper routines
>   crypto: x86/camellia - drop CTR mode implementation
>   crypto: x86/serpent - drop CTR mode implementation
>   crypto: x86/cast5 - drop CTR mode implementation
>   crypto: x86/cast6 - drop CTR mode implementation
>   crypto: x86/twofish - drop CTR mode implementation
>   crypto: x86/glue-helper - drop CTR helper routines
>   crypto: x86/des - drop CTR mode implementation
>   crypto: x86/blowfish - drop CTR mode implementation
>   crypto: x86 - add some helper macros for ECB and CBC modes
>   crypto: x86/camellia - drop dependency on glue helper
>   crypto: x86/serpent - drop dependency on glue helper
>   crypto: x86/cast5 - drop dependency on glue helper
>   crypto: x86/cast6 - drop dependency on glue helper
>   crypto: x86/twofish - drop dependency on glue helper
>   crypto: x86 - remove glue helper module
>   crypto: x86 - use local headers for x86 specific shared declarations
> 
>  arch/x86/crypto/Makefile                      |   2 -
>  arch/x86/crypto/blowfish_glue.c               | 107 -----
>  arch/x86/crypto/camellia-aesni-avx-asm_64.S   | 298 --------------
>  arch/x86/crypto/camellia-aesni-avx2-asm_64.S  | 351 ----------------
>  arch/x86/{include/asm => }/crypto/camellia.h  |  24 --
>  arch/x86/crypto/camellia_aesni_avx2_glue.c    | 198 ++-------
>  arch/x86/crypto/camellia_aesni_avx_glue.c     | 216 +---------
>  arch/x86/crypto/camellia_glue.c               | 145 ++-----
>  arch/x86/crypto/cast5_avx_glue.c              | 287 +------------
>  arch/x86/crypto/cast6-avx-x86_64-asm_64.S     |  84 ----
>  arch/x86/crypto/cast6_avx_glue.c              | 207 +---------
>  arch/x86/crypto/des3_ede_glue.c               | 104 -----
>  arch/x86/crypto/ecb_cbc_helpers.h             |  76 ++++
>  arch/x86/crypto/glue_helper-asm-avx.S         | 104 -----
>  arch/x86/crypto/glue_helper-asm-avx2.S        | 136 -------
>  arch/x86/crypto/glue_helper.c                 | 381 ------------------
>  arch/x86/crypto/serpent-avx-x86_64-asm_64.S   |  68 ----
>  arch/x86/crypto/serpent-avx.h                 |  21 +
>  arch/x86/crypto/serpent-avx2-asm_64.S         |  87 ----
>  .../{include/asm => }/crypto/serpent-sse2.h   |   0
>  arch/x86/crypto/serpent_avx2_glue.c           | 185 +--------
>  arch/x86/crypto/serpent_avx_glue.c            | 215 +---------
>  arch/x86/crypto/serpent_sse2_glue.c           | 150 ++-----
>  arch/x86/crypto/twofish-avx-x86_64-asm_64.S   |  80 ----
>  arch/x86/{include/asm => }/crypto/twofish.h   |   4 -
>  arch/x86/crypto/twofish_avx_glue.c            | 211 +---------
>  arch/x86/crypto/twofish_glue_3way.c           | 160 ++------
>  arch/x86/include/asm/crypto/glue_helper.h     | 118 ------
>  arch/x86/include/asm/crypto/serpent-avx.h     |  42 --
>  crypto/Kconfig                                |  30 +-
>  crypto/skcipher.c                             |   6 -
>  include/crypto/internal/skcipher.h            |   1 -
>  32 files changed, 326 insertions(+), 3772 deletions(-)
>  rename arch/x86/{include/asm => }/crypto/camellia.h (69%)
>  create mode 100644 arch/x86/crypto/ecb_cbc_helpers.h
>  delete mode 100644 arch/x86/crypto/glue_helper.c
>  create mode 100644 arch/x86/crypto/serpent-avx.h
>  rename arch/x86/{include/asm => }/crypto/serpent-sse2.h (100%)
>  rename arch/x86/{include/asm => }/crypto/twofish.h (80%)
>  delete mode 100644 arch/x86/include/asm/crypto/glue_helper.h
>  delete mode 100644 arch/x86/include/asm/crypto/serpent-avx.h

All applied.  Thanks.
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt



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