# git rev-parse -q --verify 9ef34630a4614ee1cd478f9859ebea55d55f10ec^{commit}
9ef34630a4614ee1cd478f9859ebea55d55f10ec
already have revision, skipping fetch
# git checkout -q -f -B kisskb 9ef34630a4614ee1cd478f9859ebea55d55f10ec
# git clean -qxdf
# < git log -1
# commit 9ef34630a4614ee1cd478f9859ebea55d55f10ec
# Author: Oliver O'Halloran <oohall@gmail.com>
# Date:   Fri Dec 7 02:17:14 2018 +1100
# 
#     powerpc/mm: Fallback to RAM if the altmap is unusable
#     
#     The "altmap" is used to provide a pool of memory that is reserved for
#     the vmemmap backing of hot-plugged memory. This is useful when adding
#     large amount of ZONE_DEVICE memory to a system with a limited amount of
#     normal memory.
#     
#     On ppc64 we use huge pages to map the vmemmap which requires the backing
#     storage to be contigious and aligned to the hugepage size. The altmap
#     implementation allows for the altmap provider to reserve a few PFNs at
#     the start of the range for it's own uses and when this occurs the
#     first chunk of the altmap is not usable for hugepage mappings. On hash
#     there is no sane way to fall back to a normal sized page mapping so we
#     fail the allocation. This results in memory hotplug failing with
#     ENOMEM when the new range doesn't fall into an existing vmemmap block.
#     
#     This patch handles this case by falling back to using system memory
#     rather than failing if we cannot allocate from the altmap. This
#     fallback should only ever be used for the first vmemmap block so it
#     should not cause excess memory consumption.
#     
#     Fixes: 7b73d978a5d0 ("mm: pass the vmem_altmap to vmemmap_populate")
#     Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < git log --format=%s --max-count=1 9ef34630a4614ee1cd478f9859ebea55d55f10ec
# < make -s -j 80 ARCH=powerpc O=/kisskb/build/powerpc-fixes_pseries_defconfig+POWERNV=n_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  pseries_defconfig
# Added to kconfig CONFIG_PPC_POWERNV=n
# yes \n | make -s -j 80 ARCH=powerpc O=/kisskb/build/powerpc-fixes_pseries_defconfig+POWERNV=n_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  oldconfig
yes: standard output: Broken pipe
# make -s -j 80 ARCH=powerpc O=/kisskb/build/powerpc-fixes_pseries_defconfig+POWERNV=n_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_pseries_defconfig+POWERNV=n_powerpc-gcc5
# Build took: 0:02:40.025010