From: Ard Biesheuvel <ardb@kernel.org>

The zero page should contain only zero bytes, and so mapping it
read-write is unnecessary. Move it to __ro_after_init instead.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/mm/mmu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 2a18637ecc15..d978b07ab7b8 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -68,7 +68,8 @@ long __section(".mmuoff.data.write") __early_cpu_boot_status;
  * Empty_zero_page is a special page that is used for zero-initialized data
  * and COW.
  */
-unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
+unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
+					__ro_after_init __aligned(PAGE_SIZE);
 EXPORT_SYMBOL(empty_zero_page);
 
 static DEFINE_SPINLOCK(swapper_pgdir_lock);
-- 
2.52.0.457.g6b5491de43-goog

On 19/01/26 10:17 PM, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@kernel.org>
> 
> The zero page should contain only zero bytes, and so mapping it
> read-write is unnecessary. Move it to __ro_after_init instead.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  arch/arm64/mm/mmu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 2a18637ecc15..d978b07ab7b8 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -68,7 +68,8 @@ long __section(".mmuoff.data.write") __early_cpu_boot_status;
>   * Empty_zero_page is a special page that is used for zero-initialized data
>   * and COW.
>   */
> -unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
> +unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
> +					__ro_after_init __aligned(PAGE_SIZE);
>  EXPORT_SYMBOL(empty_zero_page);
>  
>  static DEFINE_SPINLOCK(swapper_pgdir_lock);

A small nit - could this be the first patch in the series here ? Becasue it is
not related to other three patches.

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

On Fri, 23 Jan 2026 at 07:43, Anshuman Khandual
<anshuman.khandual@arm.com> wrote:
>
>
>
> On 19/01/26 10:17 PM, Ard Biesheuvel wrote:
> > From: Ard Biesheuvel <ardb@kernel.org>
> >
> > The zero page should contain only zero bytes, and so mapping it
> > read-write is unnecessary. Move it to __ro_after_init instead.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> >  arch/arm64/mm/mmu.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index 2a18637ecc15..d978b07ab7b8 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -68,7 +68,8 @@ long __section(".mmuoff.data.write") __early_cpu_boot_status;
> >   * Empty_zero_page is a special page that is used for zero-initialized data
> >   * and COW.
> >   */
> > -unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
> > +unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
> > +                                     __ro_after_init __aligned(PAGE_SIZE);
> >  EXPORT_SYMBOL(empty_zero_page);
> >
> >  static DEFINE_SPINLOCK(swapper_pgdir_lock);
>
> A small nit - could this be the first patch in the series here ? Becasue it is
> not related to other three patches.
>

It is related to the other three patches: the 4th patch requires it.

> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

Thanks!