RE: [PATCH v5 1/5] mm: move mirrored memory overlap checking to the outer loop
From: Liu, Yuan1
Date: Fri May 22 2026 - 03:43:56 EST
> Subject: Re: [PATCH v5 1/5] mm: move mirrored memory overlap checking to
> the outer loop
>
> On Wed, May 20, 2026 at 05:34:53AM -0400, Yuan Liu wrote:
> >Move the overlap memmap initialization check from memmap_init_range()
> >to memmap_init(), and replace the per-PFN check with a memblock-based
> >check.
>
> The description is a little simple.
>
> Even I know the purpose, I feel confused at the first glance.
Thanks for the review.
I will try to rephrase it and provide a clearer description in the next version.
> >
> >Reviewed-by: Wei Yang <richard.weiyang@xxxxxxxxx>
> >Reviewed-by: Jason Zeng <jason.zeng@xxxxxxxxx>
> >Signed-off-by: Yuan Liu <yuan1.liu@xxxxxxxxx>
> >---
> > mm/mm_init.c | 29 +++++------------------------
> > 1 file changed, 5 insertions(+), 24 deletions(-)
> >
> >diff --git a/mm/mm_init.c b/mm/mm_init.c
> >index f9f8e1af921c..24e103a402b0 100644
> >--- a/mm/mm_init.c
> >+++ b/mm/mm_init.c
> >@@ -783,28 +783,6 @@ void __meminit init_deferred_page(unsigned long pfn,
> int nid)
> > __init_deferred_page(pfn, nid);
> > }
> >
> >-/* If zone is ZONE_MOVABLE but memory is mirrored, it is an overlapped
> init */
> >-static bool __meminit
> >-overlap_memmap_init(unsigned long zone, unsigned long *pfn)
> >-{
> >- static struct memblock_region *r __meminitdata;
> >-
> >- if (mirrored_kernelcore && zone == ZONE_MOVABLE) {
> >- if (!r || *pfn >= memblock_region_memory_end_pfn(r)) {
> >- for_each_mem_region(r) {
> >- if (*pfn < memblock_region_memory_end_pfn(r))
> >- break;
> >- }
> >- }
> >- if (*pfn >= memblock_region_memory_base_pfn(r) &&
> >- memblock_is_mirror(r)) {
> >- *pfn = memblock_region_memory_end_pfn(r);
> >- return true;
> >- }
> >- }
> >- return false;
> >-}
> >-
> > /*
> > * Only struct pages that correspond to ranges defined by
> memblock.memory
> > * are zeroed and initialized by going through __init_single_page()
> during
> >@@ -891,8 +869,6 @@ void __meminit memmap_init_range(unsigned long size,
> int nid, unsigned long zone
> > * function. They do not exist on hotplugged memory.
> > */
> > if (context == MEMINIT_EARLY) {
> >- if (overlap_memmap_init(zone, &pfn))
> >- continue;
> > if (defer_init(nid, pfn, zone_end_pfn)) {
> > deferred_struct_pages = true;
> > break;
> >@@ -956,6 +932,7 @@ static void __init memmap_init(void)
> > int i, j, zone_id = 0, nid;
> >
> > for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid)
> {
> >+ struct memblock_region *r = &memblock.memory.regions[i];
> > struct pglist_data *node = NODE_DATA(nid);
> >
> > for (j = 0; j < MAX_NR_ZONES; j++) {
> >@@ -964,6 +941,10 @@ static void __init memmap_init(void)
> > if (!populated_zone(zone))
> > continue;
> >
> >+ if (mirrored_kernelcore && j == ZONE_MOVABLE &&
> >+ memblock_is_mirror(r))
> >+ continue;
> >+
>
> So you have figured out the memory layout of mirror memory?
>
> Would you mind elaborate?
I have a Xeon server, collected mirror memory layout information as below by using follow changes:
int __init_memblock memblock_mark_mirror(phys_addr_t base, phys_addr_t size)
{
- if (!mirrored_kernelcore)
+ int ret;
+ phys_addr_t end = base + size - 1;
+
+ pr_info("memblock_mark_mirror: base=%pa, size=%pa, mirrored_kernelcore=%d\n",
+ &base, &size, mirrored_kernelcore);
+
+ if (!mirrored_kernelcore) {
+ pr_info("memblock_mark_mirror: mirrored_kernelcore not enabled, skipping\n");
return 0;
+ }
system_has_some_mirror = true;
- return memblock_setclr_flag(&memblock.memory, base, size, 1, MEMBLOCK_MIRROR);
+ ret = memblock_setclr_flag(&memblock.memory, base, size, 1, MEMBLOCK_MIRROR);
+ pr_info("memblock_mark_mirror: marked [%pa-%pa] as MIRROR, ret=%d\n",
+ &base, &end, ret);
+ return ret;
}
Here is the detailed layout information:
Case 1: efibootmgr -m t -M 0
Enable mirror memory below 4GB, and no mirror memory above 4G
=== zoneinfo summary ===
node zone start_pfn end_pfn start_addr end_addr
------ ---------- ------------ ------------ ------------------ -------------
0 DMA 0x1 0xfff 0x1000 0xffffff
0 DMA32 0x1000 0xfffff 0x1000000 0xffffffff
0 Normal 0x100000 0x7fbffff 0x100000000 0x7fbfffffff
0 Movable 0x140000 0x7fbffff 0x140000000 0x7fbfffffff
1 Normal 0x7fc0000 0xff7ffff 0x7fc0000000 0xff7fffffff
1 Movable 0x8000000 0xff7ffff 0x8000000000 0xff7fffffff
node start end size flags mirror pfn_range
---- -------------------- -------------------- ------------ --------------- -------- ------------------
0 0x0000000000001000 0x000000000009dfff 0x000000000009d000 0x2 yes 0x1-0x9e
0 0x000000000009f000 0x000000000009ffff 0x0000000000001000 0x2 yes 0x9f-0xa0
0 0x0000000000100000 0x0000000066416fff 0x0000000066317000 0x2 yes 0x100-0x66417
0 0x00000000777ff000 0x00000000777fffff 0x0000000000001000 0x2 yes 0x777ff-0x77800
0 0x0000000100000000 0x000000013fffffff 0x0000000040000000 0x2 yes 0x100000-0x140000
0 0x0000000140000000 0x0000007fbfffffff 0x0000007e80000000 0x0 no 0x140000-0x7fc0000
1 0x0000007fc0000000 0x0000007fffffffff 0x0000000040000000 0x2 yes 0x7fc0000-0x8000000
1 0x0000008000000000 0x000000ff7fffffff 0x0000007f80000000 0x0 no 0x8000000-0xff80000
Case 2: efibootmgr -m t -M 25
Enable mirror memory below 4GB, and put 25% percentage memory to mirror above 4GB
=== zoneinfo summary ===
node zone start_pfn end_pfn start_addr end_addr
------ ---------- ------------ ------------ ------------------ -----------
0 DMA 0x1 0xfff 0x1000 0xffffff
0 DMA32 0x1000 0xfffff 0x1000000 0xffffffff
0 Normal 0x100000 0x603ffff 0x100000000 0x603fffffff
0 Movable 0x20c0000 0x603ffff 0x20c0000000 0x603fffffff
1 Normal 0x6040000 0xc03ffff 0x6040000000 0xc03fffffff
1 Movable 0x8040000 0xc03ffff 0x8040000000 0xc03fffffff
node start end size flags mirror pfn_range
---- -------------------- -------------------- ------------ ---------- -------- ------------------
0 0x0000000000001000 0x000000000009dfff 0x000000000009d000 0x2 yes 0x1-0x9e
0 0x000000000009f000 0x000000000009ffff 0x0000000000001000 0x2 yes 0x9f-0xa0
0 0x0000000000100000 0x0000000066416fff 0x0000000066317000 0x2 yes 0x100-0x66417
0 0x00000000777ff000 0x00000000777fffff 0x0000000000001000 0x2 yes 0x777ff-0x77800
0 0x0000000100000000 0x00000020bfffffff 0x0000001fc0000000 0x2 yes 0x100000-0x20c0000
0 0x00000020c0000000 0x000000603fffffff 0x0000003f80000000 0x0 no 0x20c0000-0x6040000
1 0x0000006040000000 0x000000803fffffff 0x0000002000000000 0x2 yes 0x6040000-0x8040000
1 0x0000008040000000 0x000000c03fffffff 0x0000004000000000 0x0 no 0x8040000-0xc040000
Case 3: efibootmgr -m f -M 25
Disable mirror memory below 4GB, and put 25% percentage memory to mirror above 4GB
=== zoneinfo summary ===
node zone start_pfn end_pfn start_addr end_addr
------ ---------- ------------ ------------ ------------------ ------------
0 DMA 0x1 0xfff 0x1000 0xffffff
0 DMA32 0x1000 0xfffff 0x1000000 0xffffffff
0 Normal 0x100000 0x60bffff 0x100000000 0x60bfffffff
0 Movable 0x20c0000 0x60bffff 0x20c0000000 0x60bfffffff
1 Normal 0x60c0000 0xc0bffff 0x60c0000000 0xc0bfffffff
1 Movable 0x80c0000 0xc0bffff 0x80c0000000 0xc0bfffffff
node start end size flags mirror pfn_range
---- -------------------- -------------------- ------------ ---------- -------- ------------------
0 0x0000000000001000 0x000000000009dfff 0x000000000009d000 0x0 no 0x1-0x9e
0 0x000000000009f000 0x000000000009ffff 0x0000000000001000 0x0 no 0x9f-0xa0
0 0x0000000000100000 0x0000000066416fff 0x0000000066317000 0x0 no 0x100-0x66417
0 0x00000000777ff000 0x00000000777fffff 0x0000000000001000 0x0 no 0x777ff-0x77800
0 0x0000000100000000 0x00000020bfffffff 0x0000001fc0000000 0x2 yes 0x100000-0x20c0000
0 0x00000020c0000000 0x00000060bfffffff 0x0000004000000000 0x0 no 0x20c0000-0x60c0000
1 0x00000060c0000000 0x00000080bfffffff 0x0000002000000000 0x2 yes 0x60c0000-0x80c0000
1 0x00000080c0000000 0x000000c0bfffffff 0x0000004000000000 0x0 no 0x80c0000-0xc0c0000
> > memmap_init_zone_range(zone, start_pfn, end_pfn,
> > &hole_pfn);
> > zone_id = j;
> >--
> >2.47.3
>
> --
> Wei Yang
> Help you, Help me