# git rev-parse -q --verify 4c6be9192dbbe4aff7d42057d7864df8a5f3baf2^{commit}
# git fetch -q -n -f git://gitlab.ozlabs.ibm.com/mirror/linux-npiggin.git kerkins
# git rev-parse -q --verify 4c6be9192dbbe4aff7d42057d7864df8a5f3baf2^{commit}
4c6be9192dbbe4aff7d42057d7864df8a5f3baf2
# git checkout -q -f -B kisskb 4c6be9192dbbe4aff7d42057d7864df8a5f3baf2
# git clean -qxdf
# < git log -1
# commit 4c6be9192dbbe4aff7d42057d7864df8a5f3baf2
# Author: Nicholas Piggin <npiggin@gmail.com>
# Date:   Fri Sep 13 22:07:01 2019 +1000
# 
#     powerpc/64s: system call support for scv/rfscv instructions
#     
#     Add support for the scv instruction on POWER9 and later CPUs.
#     
#     For now this implements the zeroth scv vector 'scv 0', as identical
#     to 'sc' system calls, with the exception that lr is not preserved, and
#     it is 64-bit only. There may yet be changes made to this ABI, so it's
#     for testing only.
#     
#     rfscv is implemented to return from scv type system calls. It can not
#     be used to return from sc system calls because those are defined to
#     preserve lr.
#     
#     In a comparison of getpid syscall, the test program had scv taking
#     about 3 more cycles in user mode (92 vs 89 for sc), due to lr handling.
#     getpid syscall throughput on POWER9 is improved by 33%, mostly due to
#     reducing mtmsr and mtspr.
#     
#     Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version
# < git log --format=%s --max-count=1 4c6be9192dbbe4aff7d42057d7864df8a5f3baf2
# < make -s -j 32 ARCH=powerpc O=/kisskb/build/npiggin_powerpc-allnoconfig_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-  allnoconfig
# < make -s -j 32 ARCH=powerpc O=/kisskb/build/npiggin_powerpc-allnoconfig_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-  help
# make -s -j 32 ARCH=powerpc O=/kisskb/build/npiggin_powerpc-allnoconfig_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-  olddefconfig
# make -s -j 32 ARCH=powerpc O=/kisskb/build/npiggin_powerpc-allnoconfig_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-  
Completed OK
# rm -rf /kisskb/build/npiggin_powerpc-allnoconfig_powerpc-gcc4.9
# Build took: 0:03:19.634251