[lkml]   [2020]   [Jan]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH v1 2/2] mm: factor out next_present_section_nr()
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

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

 \ /
  Last update: 2020-01-14 16:53    [W:0.038 / U:45.596 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site