On Fri, Nov 28, 2025 at 03:41:41PM +1100, Jordan Niethe wrote: > A future change will remove device private pages from the physical > address space. This will mean that device private pages no longer have > normal PFN and must be handled separately. > > Prepare for this by adding a HMM_PFN_DEVICE_PRIVATE flag to indicate > that a hmm_pfn contains a PFN for a device private page. > > Signed-off-by: Jordan Niethe <[email protected]> > Signed-off-by: Alistair Popple <[email protected]> > --- > include/linux/hmm.h | 2 ++ > mm/hmm.c | 2 +- > 2 files changed, 3 insertions(+), 1 deletion(-) > > diff --git a/include/linux/hmm.h b/include/linux/hmm.h > index db75ffc949a7..df571fa75a44 100644 > --- a/include/linux/hmm.h > +++ b/include/linux/hmm.h > @@ -23,6 +23,7 @@ struct mmu_interval_notifier; > * HMM_PFN_WRITE - if the page memory can be written to (requires > HMM_PFN_VALID) > * HMM_PFN_ERROR - accessing the pfn is impossible and the device should > * fail. ie poisoned memory, special pages, no vma, etc > + * HMM_PFN_DEVICE_PRIVATE - the pfn field contains a DEVICE_PRIVATE pfn. > * HMM_PFN_P2PDMA - P2P page > * HMM_PFN_P2PDMA_BUS - Bus mapped P2P transfer > * HMM_PFN_DMA_MAPPED - Flag preserved on input-to-output transformation > @@ -40,6 +41,7 @@ enum hmm_pfn_flags { > HMM_PFN_VALID = 1UL << (BITS_PER_LONG - 1), > HMM_PFN_WRITE = 1UL << (BITS_PER_LONG - 2), > HMM_PFN_ERROR = 1UL << (BITS_PER_LONG - 3), > + HMM_PFN_DEVICE_PRIVATE = 1UL << (BITS_PER_LONG - 7), > /* > * Sticky flags, carried from input to output, > * don't forget to update HMM_PFN_INOUT_FLAGS > diff --git a/mm/hmm.c b/mm/hmm.c > index 87562914670a..1cff68ade1d4 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -262,7 +262,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, > unsigned long addr, > if (is_device_private_entry(entry) && > page_pgmap(pfn_swap_entry_to_page(entry))->owner == > range->dev_private_owner) { > - cpu_flags = HMM_PFN_VALID; > + cpu_flags = HMM_PFN_VALID | HMM_PFN_DEVICE_PRIVATE;
I think you’ll need to set this flag in hmm_vma_handle_absent_pmd as well. That function handles 2M device pages. Support for 2M device pages, I believe, will be included in the 6.19 PR, but hmm_vma_handle_absent_pmd is already upstream. Matt > if (is_writable_device_private_entry(entry)) > cpu_flags |= HMM_PFN_WRITE; > new_pfn_flags = swp_offset_pfn(entry) | cpu_flags; > -- > 2.34.1 >
