On 2018/4/12 9:49, Xishi Qiu wrote: > Hi, I find CONFIG_X86_RESERVE_LOW=64 in my system, so trim_low_memory_range() > will reserve low 64kb memory. But efi_free_boot_services() will free it to > buddy system again later because BIOS set the type to EFI_BOOT_SERVICES_CODE. > > Here is the log: > ... > efi: mem03: type=3, attr=0xf, range=[0x000000000000e000-0x0000000000010000) (0MB > ... > > When call memblock_is_region_reserved(), it will set md->num_pages = 0 if the memblock region is reserved. But trim_low_memory_range() reserve the region after efi, so this breaks the logic, and efi_free_boot_services() will free the pages(efi code/data). That means trim_low_memory_range() has not reserve the low memory range. ... efi_reserve_boot_services() ... trim_low_memory_range() ... efi_free_boot_services() ... Shall we move trim_low_memory_range() before efi_reserve_boot_services()? Thanks, Xishi Qiu > . >
