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spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 12/2/25 12:20, Jordan Niethe wrote: > Hi, > > On 29/11/25 05:36, Matthew Brost wrote: >> 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 >>> Signed-off-by: Alistair Popple >>> --- >>>   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), Doesn't this break HMM_PFN_ORDER_SHIFT? The assumption is that we have 5 bits for order >>>       /* >>>        * 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. > > Thanks Matt, I agree. There will be a few more updates to this > series for 2MB device pages - I'll send the next revision on top of that > support. > I think it makes sense to build on top of v6.19 with THP support Balbir