RE: [PATCH v5 00/23] crypto: arm64 - play nice with CONFIG_PREEMPT

[Vakul Garg <vakul.garg@nxp.com>]

Hi

How does this patchset affect the throughput performance of crypto?
Is it expected to increase?

Regards

Vakul

> -----Original Message-----
> From: linux-crypto-owner@vger.kernel.org [mailto:linux-crypto-
> owner@vger.kernel.org] On Behalf Of Ard Biesheuvel
> Sent: Saturday, March 10, 2018 8:52 PM
> To: linux-crypto@vger.kernel.org
> Cc: herbert@gondor.apana.org.au; linux-arm-kernel@lists.infradead.org;
> Ard Biesheuvel <ard.biesheuvel@linaro.org>; Dave Martin
> <Dave.Martin@arm.com>; Russell King - ARM Linux
> <linux@armlinux.org.uk>; Sebastian Andrzej Siewior
> <bigeasy@linutronix.de>; Mark Rutland <mark.rutland@arm.com>; linux-rt-
> users@vger.kernel.org; Peter Zijlstra <peterz@infradead.org>; Catalin
> Marinas <catalin.marinas@arm.com>; Will Deacon
> <will.deacon@arm.com>; Steven Rostedt <rostedt@goodmis.org>; Thomas
> Gleixner <tglx@linutronix.de>
> Subject: [PATCH v5 00/23] crypto: arm64 - play nice with CONFIG_PREEMPT
> 
> As reported by Sebastian, the way the arm64 NEON crypto code currently
> keeps kernel mode NEON enabled across calls into skcipher_walk_xxx() is
> causing problems with RT builds, given that the skcipher walk API may
> allocate and free temporary buffers it uses to present the input and output
> arrays to the crypto algorithm in blocksize sized chunks (where blocksize is
> the natural blocksize of the crypto algorithm), and doing so with NEON
> enabled means we're alloc/free'ing memory with preemption disabled.
> 
> This was deliberate: when this code was introduced, each
> kernel_neon_begin() and kernel_neon_end() call incurred a fixed penalty of
> storing resp.
> loading the contents of all NEON registers to/from memory, and so doing it
> less often had an obvious performance benefit. However, in the mean time,
> we have refactored the core kernel mode NEON code, and now
> kernel_neon_begin() only incurs this penalty the first time it is called after
> entering the kernel, and the NEON register restore is deferred until returning
> to userland. This means pulling those calls into the loops that iterate over the
> input/output of the crypto algorithm is not a big deal anymore (although
> there are some places in the code where we relied on the NEON registers
> retaining their values between calls)
> 
> So let's clean this up for arm64: update the NEON based skcipher drivers to
> no longer keep the NEON enabled when calling into the skcipher walk API.
> 
> As pointed out by Peter, this only solves part of the problem. So let's tackle it
> more thoroughly, and update the algorithms to test the NEED_RESCHED flag
> each time after processing a fixed chunk of input.
> 
> Given that this issue was flagged by the RT people, I would appreciate it if
> they could confirm whether they are happy with this approach.
> 
> Changes since v4:
> - rebase onto v4.16-rc3
> - apply the same treatment to new SHA512, SHA-3 and SM3 code that landed
>   in v4.16-rc1
> 
> Changes since v3:
> - incorporate Dave's feedback on the asm macros to push/pop frames and to
> yield
>   the NEON conditionally
> - make frame_push/pop more easy to use, by recording the arguments to
>   frame_push, removing the need to specify them again when calling
> frame_pop
> - emit local symbol .Lframe_local_offset to allow code using the frame
> push/pop
>   macros to index the stack more easily
> - use the magic \@ macro invocation counter provided by GAS to generate
> unique
>   labels om the NEON yield macros, rather than relying on chance
> 
> Changes since v2:
> - Drop logic to yield only after so many blocks - as it turns out, the
>   throughput of the algorithms that are most likely to be affected by the
>   overhead (GHASH and AES-CE) only drops by ~1% (on Cortex-A57), and if
> that
>   is inacceptable, you are probably not using CONFIG_PREEMPT in the first
>   place.
> - Add yield support to the AES-CCM driver
> - Clean up macros based on feedback from Dave
> - Given that I had to add stack frame logic to many of these functions, factor
>   it out and wrap it in a couple of macros
> - Merge the changes to the core asm driver and glue code of the
> GHASH/GCM
>   driver. The latter was not correct without the former.
> 
> Changes since v1:
> - add CRC-T10DIF test vector (#1)
> - stop using GFP_ATOMIC in scatterwalk API calls, now that they are
> executed
>   with preemption enabled (#2 - #6)
> - do some preparatory refactoring on the AES block mode code (#7 - #9)
> - add yield patches (#10 - #18)
> - add test patch (#19) - DO NOT MERGE
> 
> Cc: Dave Martin <Dave.Martin@arm.com>
> Cc: Russell King - ARM Linux <linux@armlinux.org.uk>
> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: linux-rt-users@vger.kernel.org
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> 
> Ard Biesheuvel (23):
>   crypto: testmgr - add a new test case for CRC-T10DIF
>   crypto: arm64/aes-ce-ccm - move kernel mode neon en/disable into loop
>   crypto: arm64/aes-blk - move kernel mode neon en/disable into loop
>   crypto: arm64/aes-bs - move kernel mode neon en/disable into loop
>   crypto: arm64/chacha20 - move kernel mode neon en/disable into loop
>   crypto: arm64/aes-blk - remove configurable interleave
>   crypto: arm64/aes-blk - add 4 way interleave to CBC encrypt path
>   crypto: arm64/aes-blk - add 4 way interleave to CBC-MAC encrypt path
>   crypto: arm64/sha256-neon - play nice with CONFIG_PREEMPT kernels
>   arm64: assembler: add utility macros to push/pop stack frames
>   arm64: assembler: add macros to conditionally yield the NEON under
>     PREEMPT
>   crypto: arm64/sha1-ce - yield NEON after every block of input
>   crypto: arm64/sha2-ce - yield NEON after every block of input
>   crypto: arm64/aes-ccm - yield NEON after every block of input
>   crypto: arm64/aes-blk - yield NEON after every block of input
>   crypto: arm64/aes-bs - yield NEON after every block of input
>   crypto: arm64/aes-ghash - yield NEON after every block of input
>   crypto: arm64/crc32-ce - yield NEON after every block of input
>   crypto: arm64/crct10dif-ce - yield NEON after every block of input
>   crypto: arm64/sha3-ce - yield NEON after every block of input
>   crypto: arm64/sha512-ce - yield NEON after every block of input
>   crypto: arm64/sm3-ce - yield NEON after every block of input
>   DO NOT MERGE
> 
>  arch/arm64/crypto/Makefile             |   3 -
>  arch/arm64/crypto/aes-ce-ccm-core.S    | 150 ++++--
>  arch/arm64/crypto/aes-ce-ccm-glue.c    |  47 +-
>  arch/arm64/crypto/aes-ce.S             |  15 +-
>  arch/arm64/crypto/aes-glue.c           |  95 ++--
>  arch/arm64/crypto/aes-modes.S          | 562 +++++++++-----------
>  arch/arm64/crypto/aes-neonbs-core.S    | 305 ++++++-----
>  arch/arm64/crypto/aes-neonbs-glue.c    |  48 +-
>  arch/arm64/crypto/chacha20-neon-glue.c |  12 +-
>  arch/arm64/crypto/crc32-ce-core.S      |  40 +-
>  arch/arm64/crypto/crct10dif-ce-core.S  |  32 +-
>  arch/arm64/crypto/ghash-ce-core.S      | 113 ++--
>  arch/arm64/crypto/ghash-ce-glue.c      |  28 +-
>  arch/arm64/crypto/sha1-ce-core.S       |  42 +-
>  arch/arm64/crypto/sha2-ce-core.S       |  37 +-
>  arch/arm64/crypto/sha256-glue.c        |  36 +-
>  arch/arm64/crypto/sha3-ce-core.S       |  77 ++-
>  arch/arm64/crypto/sha512-ce-core.S     |  27 +-
>  arch/arm64/crypto/sm3-ce-core.S        |  30 +-
>  arch/arm64/include/asm/assembler.h     | 167 ++++++
>  arch/arm64/kernel/asm-offsets.c        |   2 +
>  crypto/testmgr.h                       | 259 +++++++++
>  22 files changed, 1392 insertions(+), 735 deletions(-)
> 
> --
> 2.15.1