Hi all, I found there is a BUG about KASLR and ZONE_MOVABLE.
When users use 'kernelcore=' parameter without 'movable_node', movable memory is evenly distributed to all nodes. The size of ZONE_MOVABLE depends on the kernel parameter 'kernelcore=' and 'movablecore='. But sometiomes, KASLR may put the uncompressed kernel to the tail position of a node, which will cause the kernel memory set as ZONE_MOVABLE. This region can not be offlined. Here is a very simple test in my qemu-kvm machine, there is only one node: The command line: [root@localhost ~]# cat /proc/cmdline BOOT_IMAGE=/vmlinuz-4.18.0-rc3+ root=/dev/mapper/fedora_localhost--live-root ro resume=/dev/mapper/fedora_localhost--live-swap rd.lvm.lv=fedora_localhost-live/root rd.lvm.lv=fedora_localhost-live/swap console=ttyS0 earlyprintk=ttyS0,115200n8 memblock=debug kernelcore=50% I use 'kernelcore=50%' here. Here is my early print result, I print the random_addr after KASLR chooses physical memory: early console in extract_kernel input_data: 0x000000000266b3b1 input_len: 0x00000000007d8802 output: 0x0000000001000000 output_len: 0x0000000001e15698 kernel_total_size: 0x0000000001a8b000 trampoline_32bit: 0x000000000009d000 booted via startup_32() Physical KASLR using RDRAND RDTSC... random_addr: 0x000000012f000000 Virtual KASLR using RDRAND RDTSC... The address for kernel is 0x000000012f000000 Here is the log of ZONE: [ 0.000000] Zone ranges: [ 0.000000] DMA [mem 0x0000000000001000-0x0000000000ffffff] [ 0.000000] DMA32 [mem 0x0000000001000000-0x00000000ffffffff] [ 0.000000] Normal [mem 0x0000000100000000-0x00000001f57fffff] [ 0.000000] Device empty [ 0.000000] Movable zone start for each node [ 0.000000] Node 0: 0x000000011b000000 [ 0.000000] Early memory node ranges [ 0.000000] node 0: [mem 0x0000000000001000-0x000000000009efff] [ 0.000000] node 0: [mem 0x0000000000100000-0x00000000bffd6fff] [ 0.000000] node 0: [mem 0x0000000100000000-0x00000001f57fffff] [ 0.000000] Initmem setup node 0 [mem 0x0000000000001000-0x00000001f57fffff] Only one node in my machine, ZONE_MOVABLE begins from 0x000000011b000000, which is lower than 0x000000012f000000. So KASLR put the kernel to the ZONE_MOVABLE. Try to solve this problem, I think there should be a new tactic in function find_zone_movable_pfns_for_nodes() of mm/page_alloc.c. If kernel is uncompressed in a tail position, then just set the memory after the kernel as ZONE_MOVABLE, at the same time, memory in other nodes will be set as ZONE_MOVABLE. If there is something wrong, pleas let me know. And any comments will be welcome. Thanks, Chao Fan