[PATCH] riscv: mm: Move dma_contiguous_reserve() after NUMA initialization

From: Eder Zulian

Date: Tue Jul 14 2026 - 14:57:55 EST


Move the dma_contiguous_reserve() call from setup_bootmem() to
misc_mem_init(), placing it after arch_numa_init(). This ensures that
NUMA topology is initialized when reserving contiguous memory for DMA.

Tested with CMA_SIZE_PERNUMA enabled and two NUMA nodes on QEMU:

qemu-system-riscv64 \
-machine virt \
-nographic \
-smp 2 -m 512M \
-numa node,nodeid=0,cpus=0,memdev=m0 \
-numa node,nodeid=1,cpus=1,memdev=m1 \
-object memory-backend-ram,id=m0,size=256M \
-object memory-backend-ram,id=m1,size=256M \
-kernel arch/riscv/boot/Image \
-append "console=ttyS0 earlycon loglevel=7 cma=16M"

Unpatched kernel's log (one global CMA pool and no per-nodepools, 16 MiB
cma-reserved):

[ 0.000000] cma: Reserved 16 MiB at 0x000000009ee00000
...
[ 0.000000] Initmem setup node 0 [mem 0x0000000080000000-0x000000008fffffff]
[ 0.000000] Initmem setup node 1 [mem 0x0000000090000000-0x000000009fffffff]
...
[ 0.056397] smp: Brought up 2 nodes, 2 CPUs
[ 0.066135] Memory: 449288K/524288K available (12279K kernel code, 5980K rwdata, 6144K rodata, 2467K init, 482K bss, 54504K reserved, 16384K cma-reserved)

Patched kernel's log (three CMA pools are created, 48 MiB total),

[ 0.000000] cma: Reserved 16 MiB at 0x000000009ee00000
[ 0.000000] cma: Reserved 16 MiB at 0x000000008ee00000
[ 0.000000] cma: Reserved 16 MiB at 0x000000009de00000
...
[ 0.054251] smp: Brought up 2 nodes, 2 CPUs
[ 0.064082] Memory: 416520K/524288K available (12279K kernel code, 5980K rwdata, 6144K rodata, 2467K init, 482K bss, 54504K reserved, 49152K cma-reserved)

Signed-off-by: Eder Zulian <ezulian@xxxxxxxxxx>
---
arch/riscv/mm/init.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 85bdcce63a3e..79a658ebe74d 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -295,8 +295,6 @@ static void __init setup_bootmem(void)
*/
if (!IS_ENABLED(CONFIG_BUILTIN_DTB))
memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
-
- dma_contiguous_reserve(dma32_phys_limit);
}

#ifdef CONFIG_RELOCATABLE
@@ -1349,6 +1347,7 @@ void __init misc_mem_init(void)
{
early_memtest(min_low_pfn << PAGE_SHIFT, max_low_pfn << PAGE_SHIFT);
arch_numa_init();
+ dma_contiguous_reserve(dma32_phys_limit);
#ifdef CONFIG_SPARSEMEM_VMEMMAP
/* The entire VMEMMAP region has been populated. Flush TLB for this region */
local_flush_tlb_kernel_range(VMEMMAP_START, VMEMMAP_END);
--
2.55.0