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    Subject[PATCH v4 00/20] crypto: arm64 - play nice with CONFIG_PREEMPT
    Date
    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@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 (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

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