From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

Move calculations of zone limits to a dedicated arch_zone_limits_init()
function.

Later MM core will use this function as an architecture specific callback
during nodes and zones initialization and thus there won't be a need to
call free_area_init() from every architecture.

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 arch/powerpc/mm/mem.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 3ddbfdbfa941..32c496bfab4f 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -221,13 +221,23 @@ static int __init mark_nonram_nosave(void)
  * anyway) will take a first dip into ZONE_NORMAL and get otherwise served by
  * ZONE_DMA.
  */
-static unsigned long max_zone_pfns[MAX_NR_ZONES];
+void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
+{
+#ifdef CONFIG_ZONE_DMA
+	max_zone_pfns[ZONE_DMA]	= min(zone_dma_limit, max_low_pfn - 1) + 1;
+#endif
+	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
+#ifdef CONFIG_HIGHMEM
+	max_zone_pfns[ZONE_HIGHMEM] = max_pfn;
+#endif
+}
 
 /*
  * paging_init() sets up the page tables - in fact we've already done this.
  */
 void __init paging_init(void)
 {
+	unsigned long max_zone_pfns[MAX_NR_ZONES];
 	unsigned long long total_ram = memblock_phys_mem_size();
 	phys_addr_t top_of_ram = memblock_end_of_DRAM();
 	int zone_dma_bits;
@@ -259,15 +269,7 @@ void __init paging_init(void)
 
 	zone_dma_limit = DMA_BIT_MASK(zone_dma_bits);
 
-#ifdef CONFIG_ZONE_DMA
-	max_zone_pfns[ZONE_DMA]	= min(max_low_pfn,
-				      1UL << (zone_dma_bits - PAGE_SHIFT));
-#endif
-	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
-#ifdef CONFIG_HIGHMEM
-	max_zone_pfns[ZONE_HIGHMEM] = max_pfn;
-#endif
-
+	arch_zone_limits_init(max_zone_pfns);
 	free_area_init(max_zone_pfns);
 
 	mark_nonram_nosave();
-- 
2.51.0

Mike Rapoport <rppt@kernel.org> writes:

> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
>
> Move calculations of zone limits to a dedicated arch_zone_limits_init()
> function.
>
> Later MM core will use this function as an architecture specific callback
> during nodes and zones initialization and thus there won't be a need to
> call free_area_init() from every architecture.
>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
>  arch/powerpc/mm/mem.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index 3ddbfdbfa941..32c496bfab4f 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -221,13 +221,23 @@ static int __init mark_nonram_nosave(void)
>   * anyway) will take a first dip into ZONE_NORMAL and get otherwise served by
>   * ZONE_DMA.
>   */
> -static unsigned long max_zone_pfns[MAX_NR_ZONES];
> +void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
> +{
> +#ifdef CONFIG_ZONE_DMA
> +	max_zone_pfns[ZONE_DMA]	= min(zone_dma_limit, max_low_pfn - 1) + 1;

Hi Mike, 

This doesn't look correct. Isn't the zone_dma_limit value in bytes actually?
Shouldn't it be -

     max_zone_pfns[ZONE_DMA] = min((zone_dma_limit >> PAGE_SHIFT) + 1, max_low_pfn);


-ritesh


> +#endif
> +	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
> +#ifdef CONFIG_HIGHMEM
> +	max_zone_pfns[ZONE_HIGHMEM] = max_pfn;
> +#endif
> +}
>  
>  /*
>   * paging_init() sets up the page tables - in fact we've already done this.
>   */
>  void __init paging_init(void)
>  {
> +	unsigned long max_zone_pfns[MAX_NR_ZONES];
>  	unsigned long long total_ram = memblock_phys_mem_size();
>  	phys_addr_t top_of_ram = memblock_end_of_DRAM();
>  	int zone_dma_bits;
> @@ -259,15 +269,7 @@ void __init paging_init(void)
>  
>  	zone_dma_limit = DMA_BIT_MASK(zone_dma_bits);
>  
> -#ifdef CONFIG_ZONE_DMA
> -	max_zone_pfns[ZONE_DMA]	= min(max_low_pfn,
> -				      1UL << (zone_dma_bits - PAGE_SHIFT));
> -#endif
> -	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
> -#ifdef CONFIG_HIGHMEM
> -	max_zone_pfns[ZONE_HIGHMEM] = max_pfn;
> -#endif
> -
> +	arch_zone_limits_init(max_zone_pfns);
>  	free_area_init(max_zone_pfns);
>  
>  	mark_nonram_nosave();
> -- 
> 2.51.0

Hi,

On Wed, Jan 07, 2026 at 09:57:34AM +0530, Ritesh Harjani wrote:
> Mike Rapoport <rppt@kernel.org> writes:
> 
> > From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> >
> > Move calculations of zone limits to a dedicated arch_zone_limits_init()
> > function.
> >
> > Later MM core will use this function as an architecture specific callback
> > during nodes and zones initialization and thus there won't be a need to
> > call free_area_init() from every architecture.
> >
> > Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> > ---
> >  arch/powerpc/mm/mem.c | 22 ++++++++++++----------
> >  1 file changed, 12 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> > index 3ddbfdbfa941..32c496bfab4f 100644
> > --- a/arch/powerpc/mm/mem.c
> > +++ b/arch/powerpc/mm/mem.c
> > @@ -221,13 +221,23 @@ static int __init mark_nonram_nosave(void)
> >   * anyway) will take a first dip into ZONE_NORMAL and get otherwise served by
> >   * ZONE_DMA.
> >   */
> > -static unsigned long max_zone_pfns[MAX_NR_ZONES];
> > +void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
> > +{
> > +#ifdef CONFIG_ZONE_DMA
> > +	max_zone_pfns[ZONE_DMA]	= min(zone_dma_limit, max_low_pfn - 1) + 1;
> 
> Hi Mike, 
> 
> This doesn't look correct. Isn't the zone_dma_limit value in bytes actually?
> Shouldn't it be -
> 
>      max_zone_pfns[ZONE_DMA] = min((zone_dma_limit >> PAGE_SHIFT) + 1, max_low_pfn);

You are right, I'll update it for v3. 
 
> -ritesh

-- 
Sincerely yours,
Mike.