Re: [PATCH v3 02/12] mm: hugetlb_vmemmap: unify VMEMMAP_{SPLIT,REMAP}_NO_TLB_FLUSH

[Oscar Salvador (SUSE)]

On Wed, Nov 04, 2026 at 10:35:00AM +0800, Muchun Song wrote:
> VMEMMAP_SPLIT_NO_TLB_FLUSH and VMEMMAP_REMAP_NO_TLB_FLUSH do not
> describe fully independent choices. A split-only walk can defer the
> PMD-split flush to a later global flush, and a remap-only walk can
> defer the final remap flush. However, when a PMD split is followed
> by PTE remapping, the split flush must happen before the PTEs are
> changed, because stale large-page translations must not overlap with
> new small-page translations that map different physical pages.
> 
> Replace the two flags with a single VMEMMAP_DEFER_TLB_FLUSH flag. The
> new name reflects that only safely batchable flushes are deferred. Keep
> split-only walks able to defer the flush, but force the split flush
> whenever a remap_pte callback is present. Callers that batch HVO work
> can still defer the final remap flush and issue their own global flush.
> 
> Current callers keep the same flushing behavior.
> 
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> Reviewed-by: Lance Yang <lance.yang@xxxxxxxxx>
> Reviewed-by: Qi Zheng <qi.zheng@xxxxxxxxx>

Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>

 

-- 
Oscar Salvador
SUSE Labs