Based on latest linux/master powernv/memtrace is the only in-kernel user that rips out random memory it never added (doesn't own) in order to allocate memory without a linear mapping. Let's stop abusing memory hot(un)plug infrastructure for that - use alloc_contig_pages() for allocating memory and remove the linear mapping manually. The original idea was discussed in: https://lkml.kernel.org/r/48340e96-7e6b-736f-9e23-d3111b915b6e@xxxxxxxxxx I only tested via QEMU TCG with a single NUMA node- see patch #8 for more details. Error handling and cleanup handling in memtrace code is a mess - that should definitely get cleaned up sooner or later. Once we have __GFP_ZERO support for alloc_contig_pages(), we can drop manual clearing. I added a TODO for now, so this series can go via the powerpc tree - the __GFP_ZERO change is then better suited via the mm tree, along with support for __GFP_ZERO. v1 -> v2: - Tweaks to patch descriptions - "powernv/memtrace: don't leak kernel memory to user space" -- Added. Reported by Michael. - "powernv/memtrace: fix crashing the kernel when enabling concurrently" -- Added, discovered while testing. - "powerpc/mm: protect linear mapping modifications by a mutex" -- Added. Although we currently won't have concurrency, this is cleaner and future-proof. - "powerepc/book3s64/hash: drop WARN_ON in hash__remove_section_mapping" -- Added. Suggested by Oscar - "powernv/memtrace: don't abuse memory hot(un)plug infrastructure for memory allocations" -- Reshuffle the code to make review easier. -- Add a TODO regarding __GFP_ZERO. Adapt to changed page clearing code. -- Use GFP_KERNEL | __GFP_THISNODE | __GFP_NOWARN for allocations. David Hildenbrand (8): powernv/memtrace: don't leak kernel memory to user space powernv/memtrace: fix crashing the kernel when enabling concurrently powerpc/mm: factor out creating/removing linear mapping powerpc/mm: protect linear mapping modifications by a mutex powerpc/mm: print warning in arch_remove_linear_mapping() powerepc/book3s64/hash: drop WARN_ON in hash__remove_section_mapping powerpc/mm: remove linear mapping if __add_pages() fails in arch_add_memory() powernv/memtrace: don't abuse memory hot(un)plug infrastructure for memory allocations arch/powerpc/mm/book3s64/hash_utils.c | 1 - arch/powerpc/mm/mem.c | 53 +++++-- arch/powerpc/platforms/powernv/Kconfig | 8 +- arch/powerpc/platforms/powernv/memtrace.c | 175 ++++++++++------------ include/linux/memory_hotplug.h | 3 + 5 files changed, 125 insertions(+), 115 deletions(-) -- 2.26.2
