[PATCH v4 6/6] memblock: Disable mirror feature if kernelcore is not specified

[Wupeng Ma]

From: Ma Wupeng <mawupeng1@xxxxxxxxxx>

If system have some mirrored memory and mirrored feature is not specified
in boot parameter, the basic mirrored feature will be enabled and this will
lead to the following situations:

- memblock memory allocation prefers mirrored region. This may have some
  unexpected influence on numa affinity.

- contiguous memory will be split into several parts if parts of them
  is mirrored memory via memblock_mark_mirror().

To fix this, variable mirrored_kernelcore will be checked in
memblock_mark_mirror(). Mark mirrored memory with flag MEMBLOCK_MIRROR iff
kernelcore=mirror is added in the kernel parameters.

Signed-off-by: Ma Wupeng <mawupeng1@xxxxxxxxxx>
---
 mm/internal.h   | 2 ++
 mm/memblock.c   | 3 +++
 mm/page_alloc.c | 2 +-
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/internal.h b/mm/internal.h
index c0f8fbe0445b..ddd2d6a46f1b 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -861,4 +861,6 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags);
 
 DECLARE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
 
+extern bool mirrored_kernelcore;
+
 #endif	/* __MM_INTERNAL_H */
diff --git a/mm/memblock.c b/mm/memblock.c
index b1d2a0009733..a9f18b988b7f 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -924,6 +924,9 @@ int __init_memblock memblock_clear_hotplug(phys_addr_t base, phys_addr_t size)
  */
 int __init_memblock memblock_mark_mirror(phys_addr_t base, phys_addr_t size)
 {
+	if (!mirrored_kernelcore)
+		return 0;
+
 	system_has_some_mirror = true;
 
 	return memblock_setclr_flag(base, size, 1, MEMBLOCK_MIRROR);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e008a3df0485..9b030aeb4983 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -356,7 +356,7 @@ static unsigned long required_kernelcore_percent __initdata;
 static unsigned long required_movablecore __initdata;
 static unsigned long required_movablecore_percent __initdata;
 static unsigned long zone_movable_pfn[MAX_NUMNODES] __initdata;
-static bool mirrored_kernelcore __meminitdata;
+bool mirrored_kernelcore __initdata;
 
 /* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */
 int movable_zone;
-- 
2.25.1