Re: [PATCH v3 2/6] mm/sparse-vmemmap: support device DAX in common vmemmap path

On Tue, Sep 29, 2026 at 01:32:27PM +0800, Muchun Song wrote:

The common vmemmap population path cannot yet handle optimized Device DAX
mappings on its own. It uses pfn_to_zone() to find the shared tail page,
but Device DAX populates its vmemmap at runtime before the ZONE_DEVICE span
is initialized.

Teach the common path to use device_zone() for runtime optimized vmemmap
population while retaining pfn_to_zone() for early boot. This allows the
same path to support both early boot mappings and Device DAX.

The backing PFN supplied by the Device DAX-specific population path is no
longer used, allowing the redundant lookup and population code to be
removed later.

Signed-off-by: Muchun Song <redacted>
Acked-by: Qi Zheng <qi.zheng@linux.dev>
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Nothing jumped out at me, feel free to add:

Reviewed-by: Lance Yang <lance.yang@linux.dev>