Re: [PATCH] alpha: Add ARCH_HAS_PTE_SPECIAL support

[Magnus Lindholm]

On Sat, Apr 4, 2026 at 3:36 AM Michael Cree <mcree@xxxxxxxxxxxx> wrote:
>
> Hi Matt,
>
> On Fri, Apr 03, 2026 at 11:00:48AM -0400, Matt Turner wrote:
> > Add _PAGE_SPECIAL using bit 19 (0x80000), which is unused in the Alpha
> > PTE layout. This enables pte_special()/pte_mkspecial() for marking PTEs
> > that are not backed by struct page (VDSO mappings, zero page,
> > io_remap_pfn_range, etc.).
> >
> > Include _PAGE_SPECIAL in _PAGE_CHG_MASK so it is preserved across
> > pte_modify() calls.
> >
> > Assisted-by: Claude:claude-opus-4-6
> > Signed-off-by: Matt Turner <mattst88@xxxxxxxxx>

Hi Matt,

These don’t apply cleanly to the current alpha tree here (v7.0-rc1-based).
As Michael also noted, the Kconfig context doesn’t match upstream, and
the index lines suggest the patches weren’t all generated from the same
snapshot, so the intended base/order isn’t entirely clear.

For a quick check, from the different patches that you submitted, I folded
in the following locally on top of current arch/alpha/Kconfig:

- ARCH_SUPPORTS_ATOMIC_RMW
- HAVE_ARCH_COMPILER_H
- ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
- ARCH_WANT_FRAME_POINTERS
- ARCH_WANT_IRQS_OFF_ACTIVATE_MM
- ARCH_HAS_PTE_SPECIAL

Built and booted fine on a UP2000+ (SMP), so the overall direction
looks good from basic testing.

Might be worth respinning from a consistent base, perhaps as a
series if that matches your intent?

Thanks,
Magnus