# git rev-parse -q --verify 49c7f0bdba27e02d44014e07d9d7723058b7b876^{commit}
49c7f0bdba27e02d44014e07d9d7723058b7b876
already have revision, skipping fetch
# git checkout -q -f -B kisskb 49c7f0bdba27e02d44014e07d9d7723058b7b876
# git clean -qxdf
# < git log -1
# commit 49c7f0bdba27e02d44014e07d9d7723058b7b876
# Author: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
# Date:   Thu Aug 27 09:39:31 2020 +0530
# 
#     powerpc/book3s64/pkeys: Optimize FTR_KUAP and FTR_KUEP disabled case
#     
#     If FTR_KUAP is disabled kernel will continue to run with the same AMR
#     value with which it was entered. Hence there is a high chance that
#     we can return without restoring the AMR value. This also helps the case
#     when applications are not using the pkey feature. In this case, different
#     applications will have the same AMR values and hence we can avoid restoring
#     AMR in this case too.
#     
#     Also avoid isync() if not really needed.
#     
#     Do the same for IAMR.
#     
#     null-syscall benchmark results:
#     
#     With smap/smep disabled:
#     Without patch:
#             957.95 ns    2778.17 cycles
#     With patch:
#             858.38 ns    2489.30 cycles
#     
#     With smap/smep enabled:
#     Without patch:
#             1017.26 ns    2950.36 cycles
#     With patch:
#             1021.51 ns    2962.44 cycles
#     
#     Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
#     Link: https://lore.kernel.org/r/20200827040931.297759-24-aneesh.kumar@linux.ibm.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 49c7f0bdba27e02d44014e07d9d7723058b7b876
# < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_tqm8xx_defconfig_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-  tqm8xx_defconfig
# < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_tqm8xx_defconfig_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-  help
# make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_tqm8xx_defconfig_powerpc-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/powerpc64-linux/bin/powerpc64-linux-  olddefconfig
# make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_tqm8xx_defconfig_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/powerpc-next_tqm8xx_defconfig_powerpc-gcc4.9
# Build took: 0:00:40.948281