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A follow-up > optimization could be to make use of the order and skip populating > subsequent PFNs. I think we should test and remove these now > > Signed-off-by: Francois Dugast > --- > mm/hmm.c | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+) > > diff --git a/mm/hmm.c b/mm/hmm.c > index f2415b4b2cdd..63ec1b18a656 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -355,6 +355,31 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, > } > > if (!pmd_present(pmd)) { > + swp_entry_t entry = pmd_to_swp_entry(pmd); > + > + /* > + * Don't fault in device private pages owned by the caller, > + * just report the PFNs. > + */ > + if (is_device_private_entry(entry) && > + pfn_swap_entry_folio(entry)->pgmap->owner == > + range->dev_private_owner) { > + unsigned long cpu_flags = HMM_PFN_VALID | > + hmm_pfn_flags_order(PMD_SHIFT - PAGE_SHIFT); > + unsigned long pfn = swp_offset_pfn(entry); > + unsigned long i; > + > + if (is_writable_device_private_entry(entry)) > + cpu_flags |= HMM_PFN_WRITE; > + > + for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) { > + hmm_pfns[i] &= HMM_PFN_INOUT_FLAGS; > + hmm_pfns[i] |= pfn | cpu_flags; > + } > + As discussed, can we remove these. > + return 0; > + } All of this be under CONFIG_ARCH_ENABLE_THP_MIGRATION > + > if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) > return -EFAULT; > return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); Balbir Singh