+ mips-fix-highmem-initialization.patch added to mm-hotfixes-unstable branch

+ mips-fix-highmem-initialization.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mips: fix HIGHMEM initialization
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mips-fix-highmem-initialization.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mips-fix-highmem-initialization.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
Subject: mips: fix HIGHMEM initialization
Date: Wed, 31 Dec 2025 12:57:01 +0200

Commit 6faea3422e3b ("arch, mm: streamline HIGHMEM freeing") overzealously
removed mem_init_free_highmem() function that beside freeing high memory
pages checked for CPU support for high memory as a prerequisite.

Partially restore mem_init_free_highmem() with a new highmem_init() name
and make it discard high memory in case there is no CPU support for it.

Link: https://lkml.kernel.org/r/20251231105701.519711-1-rppt@kernel.org
Fixes: 6faea3422e3b ("arch, mm: streamline HIGHMEM freeing")
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reported-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Cc: Chris Packham <chris.packham@alliedtelesis.co.nz>
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Cc: Jonas Jelonek <jelonek.jonas@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/mips/mm/init.c |   23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

--- a/arch/mips/mm/init.c~mips-fix-highmem-initialization
+++ a/arch/mips/mm/init.c
@@ -425,6 +425,28 @@ void __init paging_init(void)
 static struct kcore_list kcore_kseg0;
 #endif
 
+static inline void __init highmem_init(void)
+{
+#ifdef CONFIG_HIGHMEM
+	unsigned long tmp;
+
+	/*
+	 * If CPU cannot support HIGHMEM discard the memory above highstart_pfn
+	 */
+	if (cpu_has_dc_aliases) {
+		memblock_remove(PFN_PHYS(highstart_pfn), -1);
+		return;
+	}
+
+	for (tmp = highstart_pfn; tmp < highend_pfn; tmp++) {
+		struct page *page = pfn_to_page(tmp);
+
+		if (!memblock_is_memory(PFN_PHYS(tmp)))
+			SetPageReserved(page);
+	}
+#endif
+}
+
 void __init arch_mm_preinit(void)
 {
 	/*
@@ -435,6 +457,7 @@ void __init arch_mm_preinit(void)
 
 	maar_init();
 	setup_zero_pages();	/* Setup zeroed pages.  */
+	highmem_init();
 
 #ifdef CONFIG_64BIT
 	if ((unsigned long) &_text > (unsigned long) CKSEG0)
_

Patches currently in -mm which might be from rppt@kernel.org are

mips-fix-highmem-initialization.patch
alpha-introduce-arch_zone_limits_init.patch
arc-introduce-arch_zone_limits_init.patch
arm-introduce-arch_zone_limits_init.patch
arm64-introduce-arch_zone_limits_init.patch
csky-introduce-arch_zone_limits_init.patch
hexagon-introduce-arch_zone_limits_init.patch
loongarch-introduce-arch_zone_limits_init.patch
m68k-introduce-arch_zone_limits_init.patch
microblaze-introduce-arch_zone_limits_init.patch
mips-introduce-arch_zone_limits_init.patch
nios2-introduce-arch_zone_limits_init.patch
openrisc-introduce-arch_zone_limits_init.patch
parisc-introduce-arch_zone_limits_init.patch
powerpc-introduce-arch_zone_limits_init.patch
riscv-introduce-arch_zone_limits_init.patch
s390-introduce-arch_zone_limits_init.patch
sh-introduce-arch_zone_limits_init.patch
sparc-introduce-arch_zone_limits_init.patch
um-introduce-arch_zone_limits_init.patch
x86-introduce-arch_zone_limits_init.patch
xtensa-introduce-arch_zone_limits_init.patch
arch-mm-consolidate-initialization-of-nodes-zones-and-memory-map.patch
arch-mm-consolidate-initialization-of-sparse-memory-model.patch
mips-drop-paging_init.patch
x86-dont-reserve-hugetlb-memory-in-setup_arch.patch
mm-arch-consolidate-hugetlb-cma-reservation.patch
mm-hugetlb-drop-hugetlb_cma_check.patch
revert-mm-hugetlb-deal-with-multiple-calls-to-hugetlb_bootmem_alloc.patch