On Tue, Jan 14, 2020 at 11:49:19AM +0100, David Hildenbrand wrote: > memmap_init_zone() is called for a physical memory region: pfn + size > (nr_pages) > > The highest possible PFN you can have is "-1(unsigned long) >> > PFN_SHIFT". So even if you would want to add the very last section, the > PFN would still be smaller than -1UL << PFN_SECTION_SHIFT. PFN_SHIFT? I guess you mean PAGE_SHIFT. Of course PFN can be more than -1UL >> PAGE_SHIFT. Like on 32-bit x86 with PAE it is ((1ULL << 36) - 1) >> PAGE_SHIFT. That's the whole reason for PAE. The highest possible PFN must fit into phys_addr_t when shifted left by PAGE_SHIFT and must fit into unsigned long. It's can be -1UL if phys_addr_t is 64-bit. Any other limitation I miss? -- Kirill A. Shutemov
