From mboxrd@z Thu Jan 1 00:00:00 1970 From: ard.biesheuvel@linaro.org (Ard Biesheuvel) Date: Fri, 28 Mar 2014 12:05:32 +0100 Subject: [PATCH RFC 0/3] arm64: NEON crypto under CONFIG_PREEMPT Message-ID: <1396004735-15475-1-git-send-email-ard.biesheuvel@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org This series is an attempt to reduce latency under CONFIG_PREEMPT while maintaining optimal throughput otherwise, i.e., under !CONFIG_PREEMPT or while running outside of process context. In the in_interrupt() case, the calls to kernel_neon_begin and kernel_neon_end incur a fixed penalty (i.e., each call needs to stack/unstack a fixed number of registers), and preemption is not possible anyway, so the call into the crypto algorithm should just complete as fast as possible, ideally by processing all of the input in the core loop without having to spill state to memory or reload round keys (e.g., SHA-256 uses 64 32-bit round keys to process each input block of 64 bytes) In contrast, when running in process context, we should avoid hogging the CPU by spending unreasonable amounts of time inside a kernel_neon_begin/kernel_neon_end section. However, reloading those 64 32-byte round keys to process each 64-byte block one by one is far from optimal. The solution proposed here is to allow the inner loops of the crypto algorithms to test the TIF_NEED_RESCHED flag, and terminate early if it is set. This is essentially CONFIG_PREEMPT_VOLUNTARY, even under CONFIG_PREEMPT, but it is the best we can do when running with preemption disabled. Patch #1 introduces the shared asm macro, patches #2 and #3 are the SHA-1 and SHA-224/SHA-256 implementations I posted earlier, but reworked to utilize voluntary preemption. Note that this series depends on my kernel mode NEON optimization patches posted a while ago. Ard Biesheuvel (3): arm64/crypto: add shared macro to test for NEED_RESCHED arm64/crypto: SHA-1 using ARMv8 Crypto Extensions arm64/crypto: SHA-224/SHA-256 using ARMv8 Crypto Extensions arch/arm64/Kconfig | 3 + arch/arm64/Makefile | 1 + arch/arm64/crypto/Kconfig | 18 +++ arch/arm64/crypto/Makefile | 15 +++ arch/arm64/crypto/preempt.h | 28 ++++ arch/arm64/crypto/sha1-ce-core.S | 156 ++++++++++++++++++++++ arch/arm64/crypto/sha1-ce-glue.c | 201 ++++++++++++++++++++++++++++ arch/arm64/crypto/sha2-ce-core.S | 161 ++++++++++++++++++++++ arch/arm64/crypto/sha2-ce-glue.c | 280 +++++++++++++++++++++++++++++++++++++++ 9 files changed, 863 insertions(+) create mode 100644 arch/arm64/crypto/Kconfig create mode 100644 arch/arm64/crypto/Makefile create mode 100644 arch/arm64/crypto/preempt.h create mode 100644 arch/arm64/crypto/sha1-ce-core.S create mode 100644 arch/arm64/crypto/sha1-ce-glue.c create mode 100644 arch/arm64/crypto/sha2-ce-core.S create mode 100644 arch/arm64/crypto/sha2-ce-glue.c -- 1.8.3.2