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/s390/mm/init.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index e4953453d254..1c11ad84dddb 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -86,6 +86,12 @@ static void __init setup_zero_pages(void)
 	zero_page_mask = ((PAGE_SIZE << order) - 1) & PAGE_MASK;
 }
 
+void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
+{
+	max_zone_pfns[ZONE_DMA] = virt_to_pfn(MAX_DMA_ADDRESS);
+	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
+}
+
 /*
  * paging_init() sets up the page tables
  */
@@ -97,8 +103,7 @@ void __init paging_init(void)
 	sparse_init();
 	zone_dma_limit = DMA_BIT_MASK(31);
 	memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
-	max_zone_pfns[ZONE_DMA] = virt_to_pfn(MAX_DMA_ADDRESS);
-	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
+	arch_zone_limits_init(max_zone_pfns);
 	free_area_init(max_zone_pfns);
 }
 
-- 
2.51.0

On Sun, Jan 11, 2026 at 10:20:51AM +0200, Mike Rapoport wrote:

Hi Mike,

...
> +void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
> +{
> +	max_zone_pfns[ZONE_DMA] = virt_to_pfn(MAX_DMA_ADDRESS);
> +	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
> +}
> +
>  /*
>   * paging_init() sets up the page tables
>   */
> @@ -97,8 +103,7 @@ void __init paging_init(void)
>  	sparse_init();
>  	zone_dma_limit = DMA_BIT_MASK(31);
>  	memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
> -	max_zone_pfns[ZONE_DMA] = virt_to_pfn(MAX_DMA_ADDRESS);
> -	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
> +	arch_zone_limits_init(max_zone_pfns);

You move initialization of max_zone_pfns[] to a function, name the
function arch_zone_limits_init(), but leave the initializatio of
max_zone_pfns[] to zeroes outside. Should not it be brought along?

>  	free_area_init(max_zone_pfns);
>  }

Thanks!

Hi,

On Mon, Jan 12, 2026 at 08:02:48AM +0100, Alexander Gordeev wrote:
> On Sun, Jan 11, 2026 at 10:20:51AM +0200, Mike Rapoport wrote:
> 
> Hi Mike,
> 
> ...
> > +void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
> > +{
> > +	max_zone_pfns[ZONE_DMA] = virt_to_pfn(MAX_DMA_ADDRESS);
> > +	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
> > +}
> > +
> >  /*
> >   * paging_init() sets up the page tables
> >   */
> > @@ -97,8 +103,7 @@ void __init paging_init(void)
> >  	sparse_init();
> >  	zone_dma_limit = DMA_BIT_MASK(31);
> >  	memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
> > -	max_zone_pfns[ZONE_DMA] = virt_to_pfn(MAX_DMA_ADDRESS);
> > -	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
> > +	arch_zone_limits_init(max_zone_pfns);
> 
> You move initialization of max_zone_pfns[] to a function, name the
> function arch_zone_limits_init(), but leave the initializatio of
> max_zone_pfns[] to zeroes outside. Should not it be brought along?

The idea is that is the caller responsibility to initialize max_zone_pfns
to zero. After patch 24: "arch, mm: consolidate initialization of
SPARSE memory model" there is a single caller of arch_zone_limits_init()
and having initialization of max_zone_pfns() there is more optimal than
having 20-something of those.
 
> >  	free_area_init(max_zone_pfns);
> >  }
> 
> Thanks!

-- 
Sincerely yours,
Mike.