Re: [PATCH v1 2/2] arm64/mm: Add uffd write-protect support

[Catalin Marinas]

On Wed, Apr 24, 2024 at 12:10:17PM +0100, Ryan Roberts wrote:
> @@ -1248,6 +1302,7 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
>   * Encode and decode a swap entry:
>   *	bits 0-1:	present (must be zero)
>   *	bits 2:		remember PG_anon_exclusive
> + *	bit  3:		remember uffd-wp state
>   *	bits 4-53:	swap offset
>   *	bit  54:	PTE_PROT_NONE (overlays PTE_UXN) (must be zero)
>   *	bits 55-59:	swap type

Ah, I did not realise we need to free up bit 3 from the swap pte as
well. Though maybe patch 1 is fine as is but for the record, it would be
good to justify the decision to go with PTE_UXN. For this patch:

Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>