Re: [PATCH] mm/migrate_device: fix cache flush when replacing huge zero PMD

[Balbir Singh <balbirs@nvidia.com>]

On 8/17/26 4:08 PM, Hui Su wrote:
> migrate_vma_insert_huge_pmd_page() calls flush_cache_page() before
> replacing an existing huge zero PMD. However, the third argument to
> flush_cache_page() is a PFN, while addr + HPAGE_PMD_SIZE is an end
> virtual address.
> 
> More importantly, the mapping being invalidated is PMD-sized rather
> than PAGE_SIZE-sized. Flush the whole PMD range with
> flush_cache_range(), matching other huge PMD invalidation paths.
> 
> Fixes: a30b48bf1b24 ("mm/migrate_device: implement THP migration of zone device pages")
> Signed-off-by: Hui Su <sh_def@163.com>
> ---
>  mm/migrate_device.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
> index 908d2d4ec43a..098c04c1b124 100644
> --- a/mm/migrate_device.c
> +++ b/mm/migrate_device.c
> @@ -872,7 +872,7 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate,
>  
>  	if (flush) {
>  		pte_free(vma->vm_mm, pgtable);
> -		flush_cache_page(vma, addr, addr + HPAGE_PMD_SIZE);
> +		flush_cache_range(vma, addr, addr + HPAGE_PMD_SIZE);
>  		pmdp_invalidate(vma, addr, pmdp);
>  	} else {
>  		pgtable_trans_huge_deposit(vma->vm_mm, pmdp, pgtable);

Reviewed-by: Balbir Singh <balbirs@nvidia.com>