Re: [PATCH 04/12] mm: Convert vmf_insert_mixed() from using pte_devmap to pte_special

Dan Williams
2025-06-05T02:04:46Z

Alistair Popple wrote:
> DAX no longer requires device PTEs as it always has a ZONE_DEVICE page
> associated with the PTE that can be reference counted normally. Other users
> of pte_devmap are drivers that set PFN_DEV when calling vmf_insert_mixed()
> which ensures vm_normal_page() returns NULL for these entries.
>
> There is no reason to distinguish these pte_devmap users so in order to
> free up a PTE bit use pte_special instead for entries created with
> vmf_insert_mixed(). This will ensure vm_normal_page() will continue to
> return NULL for these pages.
>
> Architectures that don't support pte_special also don't support pte_devmap
> so those will continue to rely on pfn_valid() to determine if the page can
> be mapped.

Looks good,

Reviewed-by: Dan Williams <dan.j.williams@intel.com>