Mike Rapoport <[email protected]> writes:
> Hi Ritesh,
>
> On Fri, Feb 27, 2026 at 10:39:53PM +0530, Ritesh Harjani wrote:
>> Sourabh Jain <[email protected]> writes:
>>
>> > I noticed CMA init for fadump crashkernel memory is failing.
>> >
>> > [ 0.000000] cma: pageblock_order not yet initialized. Called during
>> > early boot?
>> > [ 0.000000] fadump: Failed to init cma area for firmware-assisted
>> > dump,-22
>> >
>> >
>> > kernel command-line:
>> > BOOT_IMAGE=(ieee1275//vdevice/v-scsi@30000070/disk@8100000000000000,msdos2)/vmlinuz-7.0.0-rc1+
>> >
>> > root=/dev/mapper/rhel_ltcden3--lp12-root ro
>> > rd.lvm.lv=rhel_ltcden3-lp12/root rd.lvm.lv=rhel_ltcden3-lp12/swap
>> > fadump=on crashkernel=3G
>> >
>> >
>> > Same issue with kdump CMA reservation:
>> >
>> > [ 0.000000][ T0] cma: pageblock_order not yet initialized. Called
>> > during early boot?
>>
>> Good that we added those debug prints ;)
>>
>> I think I know what went wrong, as part of this arch,mm consolidation
>> patch series [1], I think the order of initialization is changed.
>>
>> With this patch the new order is ...
>> start_kernel()
>> - setup_arch()
>> - xxx_cma_reserve();
>> - mm_core_init_early()
>> - free_area_init()
>> - sparse_init()
>> - set_pageblock_order() // this sets the pageblock_order.
>>
>> Whereas earlier set_pageblock_order() was called from initmem_init(),
>> just before cma reservations were being made.
>>
>> start_kernel()
>> - setup_arch()
>> - initmem_init()
>> - sparse_init()
>> - set_pageblock_order(); // this sets the pageblock_order
>> - xxx_cma_reserve();
>>
>> So that means, pageblock_order is not initialized before these cma
>> reservation function calls, hence we are seeing these failures.
>>
>> setup_arch() {
>> ...
>>
>> /*
>> * Reserve large chunks of memory for use by CMA for kdump, fadump, KVM
>> and
>> * hugetlb. These must be called after initmem_init(), so that
>> * pageblock_order is initialised.
>> */
>> fadump_cma_init();
>> kdump_cma_reserve();
>> kvm_cma_reserve();
>>
>> ...
>> }
>>
>>
>> So what if we do..
>>
>> start_kernel() {
>> ...
>> setup_arch(&command_line);
>> mm_core_init_early();
>> setup_arch_post_mm_core_init(); // and here we call CMA reservation
>> functions ?
>
> Unless I'm missing something these cma reservations can be moved to
> arch_mm_preinit().
> It runs after mm_core_init_early() and before memblock moves the free
> memory to the buddy.
>
Right. I think, we should be able to use that...
@Sourabh,
I don't have access to the systems (travelling back...). Could you
please give this a try?
diff --git a/arch/powerpc/kernel/setup-common.c
b/arch/powerpc/kernel/setup-common.c
index cb5b73adc250..b1761909c23f 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -35,7 +35,6 @@
#include <linux/of_irq.h>
#include <linux/hugetlb.h>
#include <linux/pgtable.h>
-#include <asm/kexec.h>
#include <asm/io.h>
#include <asm/paca.h>
#include <asm/processor.h>
@@ -995,15 +994,6 @@ void __init setup_arch(char **cmdline_p)
initmem_init();
- /*
- * Reserve large chunks of memory for use by CMA for kdump, fadump, KVM
and
- * hugetlb. These must be called after initmem_init(), so that
- * pageblock_order is initialised.
- */
- fadump_cma_init();
- kdump_cma_reserve();
- kvm_cma_reserve();
-
early_memtest(min_low_pfn << PAGE_SHIFT, max_low_pfn << PAGE_SHIFT);
if (ppc_md.setup_arch)
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 29bf347f6012..5ba947e4fe37 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -30,6 +30,10 @@
#include <asm/setup.h>
#include <asm/fixmap.h>
+#include <asm/fadump.h>
+#include <asm/kexec.h>
+#include <asm/kvm_ppc.h>
+
#include <mm/mmu_decl.h>
unsigned long long memory_limit __initdata;
@@ -268,6 +272,16 @@ void __init paging_init(void)
void __init arch_mm_preinit(void)
{
+
+ /*
+ * Reserve large chunks of memory for use by CMA for kdump, fadump, KVM
+ * and hugetlb. These must be called after pageblock_order is
+ * initialised.
+ */
+ fadump_cma_init();
+ kdump_cma_reserve();
+ kvm_cma_reserve();
+
/*
* book3s is limited to 16 page sizes due to encoding this in
* a 4-bit field for slices.
-ritesh
>> References:
>> [1]:
>> https://lore.kernel.org/linuxppc-dev/[email protected]/T/#m5adf1a845e0a0867066c4f7055f28e6304b73fa5
>> [2]:
>> https://lore.kernel.org/all/3ae208e48c0d9cefe53d2dc4f593388067405b7d.1729146153.git.ritesh.l...@gmail.com/
>>
>>
>> -ritesh
>
> --
> Sincerely yours,
> Mike.
