[PATCH v5 2/4] armv8: mmu: teach the pagetable dumper to show explicit FAULT maps

[Ilias Apalodimas]

On Mon, 18 May 2026 at 12:00, Casey Connolly <casey.connolly at linaro.org> wrote:
>
> When a region is explicitly unmapped (like with
> mmu_change_region_attr(.... PTE_TYPE_FAULT)) the address translation
> still remains but won't be used since the region is marked invalid.
> Print these regions when we dump the pagetable to help with debugging.
>
> Signed-off-by: Casey Connolly <casey.connolly at linaro.org>
> ---
>  arch/arm/cpu/armv8/cache_v8.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/cpu/armv8/cache_v8.c b/arch/arm/cpu/armv8/cache_v8.c
> index 97a1c39ed268..2800ba57a464 100644
> --- a/arch/arm/cpu/armv8/cache_v8.c
> +++ b/arch/arm/cpu/armv8/cache_v8.c
> @@ -533,9 +533,9 @@ static void __pagetable_walk(u64 addr, u64 tcr, int level, pte_walker_cb_t cb, v
>
>                 if (exit)
>                         return;
>
> -               if (pte_type(&pte) == PTE_TYPE_FAULT)
> +               if (!pte)
>                         continue;
>
>                 attrs = pte & ALL_ATTRS;
>                 /* If we're currently inside a block or set of pages */
> @@ -572,9 +572,9 @@ static void __pagetable_walk(u64 addr, u64 tcr, int level, pte_walker_cb_t cb, v
>
>                         /* Go down a level */
>                         __pagetable_walk(_addr, tcr, level + 1, cb, priv);
>                         state[level] = WALKER_STATE_START;
> -               } else if (pte_type(&pte) == PTE_TYPE_BLOCK || pte_type(&pte) == PTE_TYPE_PAGE) {
> +               } else {
>                         /* We foud a block or page, start walking */
>                         entry_start = pte;
>                         state[level] = WALKER_STATE_REGION;
>                 }
> @@ -707,8 +707,12 @@ static bool pagetable_print_entry(u64 start_attrs, u64 end, int va_bits, int lev
>  {
>         u64 _addr = start_attrs & GENMASK_ULL(va_bits, PAGE_SHIFT);
>         int indent = va_bits < 39 ? level - 1 : level;
>
> +       /* Ignore empty blocks */
> +       if (!start_attrs)
> +               return false;

I am not sure I am following this one. This one get the value of
TTBR_ELx. What are we trying to prevent? Perhaps we should move the
check to walk_pagetable()?

Cheers
/Ilias
> +
>         printf("%*s", indent * 2, "");
>         if (PTE_IS_TABLE(start_attrs, level))
>                 printf("[%#016llx]%19s", _addr, "");
>         else
>
> --
> 2.53.0
>