On 07.04.21 19:26, Mike Rapoport wrote:
From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
---
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
