On Thu, Aug 22, 2013 at 04:35:29AM +0100, Leizhen (ThunderTown, Euler) wrote: > This problem is on ARM64. When CONFIG_ARM64_64K_PAGES is not opened, the memory > map size can be 2M(section) and 4K(PAGE). First, OS will create map for pgd > (level 1 table) and level 2 table which in swapper_pg_dir. Then, OS register > mem block into memblock.memory according to memory node in fdt, like memory@0, > and create map in setup_arch-->paging_init. If all mem block start address and > size is integral multiple of 2M, there is no problem, because we will create 2M > section size map whose entries locate in level 2 table. But if it is not > integral multiple of 2M, we should create level 3 table, which granule is 4K. > Now, current implementtion is call early_alloc-->memblock_alloc to alloc memory > for level 3 table. This function will find a 4K free memory which locate in > memblock.memory tail(high address), but paging_init is create map from low > address to high address, so new alloced memory is not mapped, write page talbe > entry to it will trigger exception. I see how this can happen. There is a memblock_set_current_limit to PGDIR_SIZE (1GB, we have a pre-allocated pmd) and in my tests I had at least 1GB of RAM which got mapped first and didn't have this problem. I'll come up with a patch tomorrow. -- Catalin P.S. Please try to send plain-text (rather than HTML) emails only, with nicely wrapped lines. Thanks. -- 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>