On 1/7/19 10:13 PM, Pingfan Liu wrote: > On Tue, Jan 8, 2019 at 1:42 AM Dave Hansen <dave.hansen@xxxxxxxxx> wrote: >> Why is this 0x100000 open-coded? Why is this needed *now*? >> > > Memory under 1MB should be used by BIOS. For x86_64, after > e820__memblock_setup(), the memblock allocator has already been ready > to work. But there are two factors to in order to > set_alloc_range(0x100000, end). The major one is to be compatible with > x86_32, please refer to alloc_low_pages->memblock_find_in_range() uses > [min_pfn_mapped, max_pfn_mapped] to limit the range, which is ready to > be allocated from. The minor one is to prevent unexpected allocation > from memblock allocator through allow_low_pages() at very early stage. Wow, that's a ton of critical information which was neither commented upon or referenced in the changelog. Can you fix this up in the next version, please?
