Hi,
On 2026-01-02 08:59:58 +0200, Mike Rapoport wrote:
From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
To initialize node, zone and memory map data structures every architecture
calls free_area_init() during setup_arch() and passes it an array of zone
limits.
Beside code duplication it creates "interesting" ordering cases between
allocation and initialization of hugetlb and the memory map. Some
architectures allocate hugetlb pages very early in setup_arch() in certain
cases, some only create hugetlb CMA areas in setup_arch() and sometimes
hugetlb allocations happen mm_core_init().
With arch_zone_limits_init() helper available now on all architectures it
is no longer necessary to call free_area_init() from architecture setup
code. Rather core MM initialization can call arch_zone_limits_init() in a
single place.
This allows to unify ordering of hugetlb vs memory map allocation and
initialization.
Remove the call to free_area_init() from architecture specific code and
place it in a new mm_core_init_early() function that is called immediately
after setup_arch().
After this refactoring it is possible to consolidate hugetlb allocations
and eliminate differences in ordering of hugetlb and memory map
initialization among different architectures.
As the first step of this consolidation move hugetlb_bootmem_alloc() to
mm_core_early_init().
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
This breaks boot on my Raspberry Pi 1. The reason seems to be the use of
page_folio() when initializing the dynamically allocated zero page in
arm, which doesn't work when free_area_init() hasn't been called yet.
The following oopses are generated:
Booting Linux on physical CPU 0x0
Linux version 6.19.0-rc3-03898-g7975b0084358 (klara@soda.int.kasm.eu) (armv6j-unknown-linux-gnueabihf-gcc (Gentoo 15.2.1_p20251122 p3) 15.2.1 20251122, GNU ld (Gentoo 2.45.1 p1) 2.45.1) #451 Fri Jan 2 20:26:00 CET 2026
CPU: ARMv6-compatible processor [410fb767] revision 7 (ARMv7), cr=00c5387d
CPU: PIPT / VIPT nonaliasing data cache, VIPT nonaliasing instruction cache
OF: fdt: Machine model: Raspberry Pi Model B Rev 2
earlycon: pl11 at MMIO32 0x20201000 (options '')
printk: legacy bootconsole [pl11] enabled
Memory policy: Data cache writeback
Reserved memory: created CMA memory pool at 0x19400000, size 64 MiB
OF: reserved mem: initialized node linux,cma, compatible id shared-dma-pool
OF: reserved mem: 0x19400000..0x1d3fffff (65536 KiB) map reusable linux,cma
8<--- cut here ---
Unable to handle kernel paging request at virtual address 003dfb44 when read
[003dfb44] *pgd=00000000
Internal error: Oops: 5 [#1] ARM
CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.19.0-rc3-03898-g7975b0084358 #451 NONE
Hardware name: BCM2835
PC is at paging_init (include/linux/page-flags.h:284 (discriminator 2) arch/arm/mm/mmu.c:1790 (discriminator 2))
LR is at paging_init (arch/arm/mm/mmu.c:1789 (discriminator 1))
pc : lr : psr: 600000d3
sp : c0d01ef8 ip : defdb000 fp : 0000000b
r10: 00200000 r9 : d9400000 r8 : ffe00000
r7 : c0d09050 r6 : c0d0902c r5 : c0d43d40 r4 : 0001efda
r3 : c0dab20c r2 : 00000000 r1 : 003dfb40 r0 : 00000000
Flags: nZCv IRQs off FIQs off Mode SVC_32 ISA ARM Segment none
Control: 00c5387d Table: 00004008 DAC: 00000051
Register r0 information: NULL pointer
Register r1 information: non-paged memory
Register r2 information: NULL pointer
Register r3 information:
8<--- cut here ---
Unable to handle kernel paging request at virtual address 0001b564 when read
[0001b564] *pgd=00000000
Internal error: Oops: 5 [#2] ARM
CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.19.0-rc3-03898-g7975b0084358 #451 NONE
Hardware name: BCM2835
PC is at kmem_dump_obj (mm/slab.h:142 (discriminator 2) mm/slab.h:178 (discriminator 2) mm/slab_common.c:609 (discriminator 2))
LR is at 0x1
pc : lr : psr: 200001d3
sp : c0d01cc8 ip : 00000000 fp : 0000000b
r10: 00200000 r9 : c0dab1dc r8 : 00000000
r7 : 00000005 r6 : 00000dab r5 : 0001b560 r4 : c0dab20c
r3 : c0dc2058 r2 : 1f000000 r1 : 00c00000 r0 : 00000001
Flags: nzCv IRQs off FIQs off Mode SVC_32 ISA ARM Segment none
Control: 00c5387d Table: 00004008 DAC: 00000051
Register r0 information: non-paged memory
Register r1 information: non-paged memory
Register r2 information: non-paged memory
Register r3 information:
8<--- cut here ---
and the second one repeats for some time afterwards.
I experimented a little by allocating the zero page statically as many
other arches do which fixes the issue as it does not need to be
initialized at this point anymore, though I have no idea if that's
appropriate.
Regards,
Klara Modin
...
quoted hunk ↗ jump to hunk
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index bdcc3639681f..a8f7b4084715 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -118,15 +118,6 @@ void __init arch_zone_limits_init(unsigned long *max_zone_pfn)
#endif
}
-static void __init zone_sizes_init(unsigned long min, unsigned long max_low,
- unsigned long max_high)
-{
- unsigned long max_zone_pfn[MAX_NR_ZONES] = { 0 };
-
- arch_zone_limits_init(max_zone_pfn);
- free_area_init(max_zone_pfn);
-}
-
#ifdef CONFIG_HAVE_ARCH_PFN_VALID
int pfn_valid(unsigned long pfn)
{@@ -222,13 +213,6 @@ void __init bootmem_init(void)
* done after the fixed reservations
*/
sparse_init();
-
- /*
- * Now free the memory - free_area_init needs
- * the sparse mem_map arrays initialized by sparse_init()
- * for memmap_init_zone(), otherwise all PFNs are invalid.
- */
- zone_sizes_init(min_low_pfn, max_low_pfn, max_pfn);
}
/*
...
quoted hunk ↗ jump to hunk
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 628c0e0ac313..64d6f9c15ef1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -45,6 +45,7 @@ struct pt_regs;
struct folio_batch;
void arch_mm_preinit(void);
+void mm_core_init_early(void);
void mm_core_init(void);
void init_mm_internals(void);
@@ -3536,7 +3537,7 @@ static inline unsigned long get_num_physpages(void)
}
/*
- * Using memblock node mappings, an architecture may initialise its
+ * FIXME: Using memblock node mappings, an architecture may initialise its
* zones, allocate the backing mem_map and account for memory holes in an
* architecture independent manner.
*
@@ -3551,7 +3552,6 @@ static inline unsigned long get_num_physpages(void)
* memblock_add_node(base, size, nid, MEMBLOCK_NONE)
* free_area_init(max_zone_pfns);
*/
-void free_area_init(unsigned long *max_zone_pfn);
void arch_zone_limits_init(unsigned long *max_zone_pfn);
unsigned long node_map_pfn_alignment(void);
extern unsigned long absent_pages_in_range(unsigned long start_pfn,
diff --git a/init/main.c b/init/main.c
index b84818ad9685..445b5643ecec 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1025,6 +1025,7 @@ void start_kernel(void)
page_address_init();
pr_notice("%s", linux_banner);
setup_arch(&command_line);
+ mm_core_init_early();
/* Static keys and static calls are needed by LSMs */
jump_label_init();
static_call_init();diff --git a/mm/mm_init.c b/mm/mm_init.c
index fc2a6f1e518f..ffc4a0f1fee9 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1810,7 +1810,6 @@ static void __init set_high_memory(void)
/**
* free_area_init - Initialise all pg_data_t and zone data
- * @max_zone_pfn: an array of max PFNs for each zone
*
* This will call free_area_init_node() for each active node in the system.
* Using the page ranges provided by memblock_set_node(), the size of each
@@ -1821,17 +1820,14 @@ static void __init set_high_memory(void)
* starts where the previous one ended. For example, ZONE_DMA32 starts
* at arch_max_dma_pfn.
*/
-void __init free_area_init(unsigned long *max_zone_pfn)
+static void __init free_area_init(void)
{
+ unsigned long max_zone_pfn[MAX_NR_ZONES] = { 0 };
unsigned long start_pfn, end_pfn;
int i, nid, zone;
bool descending;
- /* Record where the zone boundaries are */
- memset(arch_zone_lowest_possible_pfn, 0,
- sizeof(arch_zone_lowest_possible_pfn));
- memset(arch_zone_highest_possible_pfn, 0,
- sizeof(arch_zone_highest_possible_pfn));
+ arch_zone_limits_init(max_zone_pfn);
start_pfn = PHYS_PFN(memblock_start_of_DRAM());
descending = arch_has_descending_max_zone_pfns();@@ -2681,13 +2677,19 @@ void __init __weak mem_init(void)
{
}
+void __init mm_core_init_early(void)
+{
+ hugetlb_bootmem_alloc();
+
+ free_area_init();
+}
+
/*
* Set up kernel memory allocators
*/
void __init mm_core_init(void)
{
arch_mm_preinit();
- hugetlb_bootmem_alloc();
/* Initializations relying on SMP setup */
BUILD_BUG_ON(MAX_ZONELISTS > 2);--
2.51.0