[PATCH v4 00/20] crypto: arm64 - play nice with CONFIG_PREEMPT

[Ard Biesheuvel]

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.

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@xxxxxxx>
Cc: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: linux-rt-users@xxxxxxxxxxxxxxx
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Ard Biesheuvel (20):
  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
  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/include/asm/assembler.h     | 154 ++++++
 arch/arm64/kernel/asm-offsets.c        |   2 +
 crypto/testmgr.h                       | 259 +++++++++
 19 files changed, 1285 insertions(+), 695 deletions(-)

-- 
2.11.0