Thanks for the response David. On Fri, Sep 24, 2021 at 10:17:46AM +0200, David Hildenbrand wrote: > no-map means that no direct mapping is to be created, right? We would still > have a memmap IIRC, and the pages are PG_reserved. > > Again, I think this is very similar to just having no-map regions like > random memory holes within the existing memory layout. For those curious, see __reserved_mem_alloc_size() > early_init_dt_alloc_reserved_memory_arch() > memblock_mark_nomap() - the 'no-map' attribute is read in __reserved_mem_alloc_size() and the pre-requisite steps need to have the relevant struct pages marked as PG_reserved are taken in memblock_mark_nomap(). > What Chris proposes here is very similar to > arch/x86/mm/init_64.c:update_end_of_memory_vars() called during > arch_add_memory()->add_pages() on x86-64. > For other's reference, the patch was derived from what x86 is doing with max_pfn (such that we also set max_low_pfn as is done in arm64's mm/init.c.
