Hi, I am testing mem-hotplug on a qemu virtual machine. I executed the following command to notify memory hot-add event by hand. % echo start_address_of_new_memory > /sys/devices/system/memory/probe To a different start_address_of_new_memory I got different results. The results are as follows: MBSC-x86_64 /sys/devices/system/memory # ls block_size_bytes memory2 memory5 power memory0 memory3 memory6 probe memory1 memory4 memory7 uevent MBSC-x86_64 /sys/devices/system/memory # echo 0x70000000 > probe MBSC-x86_64 /sys/devices/system/memory # echo 0x78000000 > probe -sh: echo: write error: File exists MBSC-x86_64 /sys/devices/system/memory # echo 0x80000000 > probe -sh: echo: write error: File exists MBSC-x86_64 /sys/devices/system/memory # echo 0x88000000 > probe -sh: echo: write error: File exists MBSC-x86_64 /sys/devices/system/memory # echo 0x8f000000 > probe -sh: echo: write error: Invalid argument MBSC-x86_64 /sys/devices/system/memory # echo 0x90000000 > probe -sh: echo: write error: File exists MBSC-x86_64 /sys/devices/system/memory # echo 0xff0000000 > probe MBSC-x86_64 /sys/devices/system/memory # ls block_size_bytes memory2 memory510 probe memory0 memory3 memory6 uevent memory1 memory4 memory7 memory14 memory5 power MBSC-x86_64 /sys/devices/system/memory # echo 0xfff0000000 > probe MBSC-x86_64 /sys/devices/system/memory # ls block_size_bytes memory2 memory510 power memory0 memory3 memory6 probe memory1 memory4 memory7 uevent memory14 memory5 memory8190 The qemu virtual machine's physical memory size is 2048M, and the boot memory is 1024M. MBSC-x86_64 / # cat /proc/meminfo MemTotal: 1018356 kB MBSC-x86_64 / # cat /sys/devices/system/memory/block_size_bytes 8000000 Three questions: 1. The machine's physical memory size is 2048M, why echo 0x78000000 as the start_address_of_new_memory failed ? 2. Why echo 0x8f000000 as the start_address_of_new_memory, the error message is different ? 3. Why echo 0xfff0000000 as the start_address_of_new_memory succeeded ? 0xfff0000000 has exceeded the machine's physical memory size. Best regards! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>