Messages in this thread | | | From | David Hildenbrand <> | Subject | Re: [RFC/RFT PATCH 1/3] memblock: update initialization of reserved pages | Date | Wed, 14 Apr 2021 17:12:11 +0200 |
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On 07.04.21 19:26, Mike Rapoport wrote: > From: Mike Rapoport <rppt@linux.ibm.com> > > The struct pages representing a reserved memory region are initialized > using reserve_bootmem_range() function. This function is called for each > reserved region just before the memory is freed from memblock to the buddy > page allocator. > > The struct pages for MEMBLOCK_NOMAP regions are kept with the default > values set by the memory map initialization which makes it necessary to > have a special treatment for such pages in pfn_valid() and > pfn_valid_within().
I assume these pages are never given to the buddy, because we don't have a direct mapping. So to the kernel, it's essentially just like a memory hole with benefits.
I can spot that we want to export such memory like any special memory thingy/hole in /proc/iomem -- "reserved", which makes sense.
I would assume that MEMBLOCK_NOMAP is a special type of *reserved* memory. IOW, that for_each_reserved_mem_range() should already succeed on these as well -- we should mark anything that is MEMBLOCK_NOMAP implicitly as reserved. Or are there valid reasons not to do so? What can anyone do with that memory?
I assume they are pretty much useless for the kernel, right? Like other reserved memory ranges.
> > Split out initialization of the reserved pages to a function with a > meaningful name and treat the MEMBLOCK_NOMAP regions the same way as the > reserved regions and mark struct pages for the NOMAP regions as > PageReserved. > > Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> > --- > mm/memblock.c | 23 +++++++++++++++++++++-- > 1 file changed, 21 insertions(+), 2 deletions(-) > > diff --git a/mm/memblock.c b/mm/memblock.c > index afaefa8fc6ab..6b7ea9d86310 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -2002,6 +2002,26 @@ static unsigned long __init __free_memory_core(phys_addr_t start, > return end_pfn - start_pfn; > } > > +static void __init memmap_init_reserved_pages(void) > +{ > + struct memblock_region *region; > + phys_addr_t start, end; > + u64 i; > + > + /* initialize struct pages for the reserved regions */ > + for_each_reserved_mem_range(i, &start, &end) > + reserve_bootmem_region(start, end); > + > + /* and also treat struct pages for the NOMAP regions as PageReserved */ > + for_each_mem_region(region) { > + if (memblock_is_nomap(region)) { > + start = region->base; > + end = start + region->size; > + reserve_bootmem_region(start, end); > + } > + } > +} > + > static unsigned long __init free_low_memory_core_early(void) > { > unsigned long count = 0; > @@ -2010,8 +2030,7 @@ static unsigned long __init free_low_memory_core_early(void) > > memblock_clear_hotplug(0, -1); > > - for_each_reserved_mem_range(i, &start, &end) > - reserve_bootmem_region(start, end); > + memmap_init_reserved_pages(); > > /* > * We need to use NUMA_NO_NODE instead of NODE_DATA(0)->node_id >
-- Thanks,
David / dhildenb
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