Using release 4.8.17 it seems to need >400MB to initialize itself. But "crashkernel=" option cannot allocate enough space. I tried "crashkernel=512M" It gives me 256MB below 4GB, and 512M above 4GB, but only seems to use the 256MB region. I tried "crashkernel=0,low crashkernel=512M", but the reservation failed. Log: ---- [ 0.000000] ???DEBUG: Calling reserve_crashkernel() ... [ 0.000000] ???DEBUG: reserve_crashkernel() TOP... [ 0.000000] kexec_core: ???DEBUG: parse_crashkernel_simple() Bottom: Rtn OK [ 0.000000] kexec_core: ???DEBUG: parse_crashkernel_simple() Bottom: Rtn OK: crash_size: 536870912, crash_base:0 [ 0.000000] ???DEBUG: parse_crashkernel() ret: 0 [ 0.000000] ???DEBUG: (1) high:0, total_mem:33949503488, crash_size:536870912, crash_base:0 [ 0.000000] reserve_crashkernel(): (a) About to call memblock_find_in_range()... [ 0.000000] ???DEBUG: memblock_find_in_range_node(): size : 536870912 [ 0.000000] ???DEBUG: memblock_find_in_range_node(): align: 16777216 [ 0.000000] ???DEBUG: memblock_find_in_range_node(): start: 16777216 [ 0.000000] ???DEBUG: memblock_find_in_range_node(): end : 939524096 [ 0.000000] ???DEBUG: memblock_find_in_range_node(): nid : -1 [ 0.000000] ???DEBUG: memblock_find_in_range_node(): flags: 0x00000000 [ 0.000000] ???DEBUG: [memblock_find_in_range_node():263] New start: 16777216 [ 0.000000] ???DEBUG: [memblock_find_in_range_node():264] New end : 939524096 [ 0.000000] ???DEBUG: [__memblock_find_range_top_down():181] start: 16777216 [ 0.000000] ???DEBUG: [__memblock_find_range_top_down():182] end : 939524096 [ 0.000000] ???DEBUG: [__memblock_find_range_top_down():183] size : 536870912 [ 0.000000] ???DEBUG: [__memblock_find_range_top_down():184] align: 16777216 [ 0.000000] ???DEBUG: [__memblock_find_range_top_down():192] this_end (354730008) < size (536870912)...continue...: -2118107472 [ 0.000000] ???DEBUG: [__memblock_find_range_top_down():192] this_end (354496536) < size (536870912)...continue...: -2118107472 [ 0.000000] ???DEBUG: [__memblock_find_range_top_down():192] this_end (354488344) < size (536870912)...continue...: -2118107472 [ 0.000000] ???DEBUG: [__memblock_find_range_top_down():192] this_end (16777216) < size (536870912)...continue...: -2118107472 [ 0.000000] ???DEBUG: [__memblock_find_range_top_down():192] this_end (16777216) < size (536870912)...continue...: -2118107472 [ 0.000000] ???DEBUG: [__memblock_find_range_top_down():192] this_end (16777216) < size (536870912)...continue...: -2118107472 [ 0.000000] ???DEBUG: [__memblock_find_range_top_down():212] Returns Zero [ 0.000000] crashkernel reservation failed - No suitable area found.