Re: [PATCH v2 1/2] mm/hmm: fault non-owner device private entries

Thanks Ralph, please add:

Reviewed-by: Alistair Popple apopple@nvidia.com

However I think the fixes tag is wrong, see below.

Ralph Campbell rcampbell@nvidia.com writes:

If hmm_range_fault() is called with the HMM_PFN_REQ_FAULT flag and a device private PTE is found, the hmm_range::dev_private_owner page is used to determine if the device private page should not be faulted in. However, if the device private page is not owned by the caller, hmm_range_fault() returns an error instead of calling migrate_to_ram() to fault in the page.

Cc: stable@vger.kernel.org Fixes: 76612d6ce4cc ("mm/hmm: reorganize how !pte_present is handled in hmm_vma_handle_pte()")

This should be 08ddddda667b ("mm/hmm: check the device private page owner in hmm_range_fault()")

Signed-off-by: Ralph Campbell rcampbell@nvidia.com Reported-by: Felix Kuehling felix.kuehling@amd.com

---

mm/hmm.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c index 3fd3242c5e50..f2aa63b94d9b 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -212,14 +212,6 @@ int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr, unsigned long end, unsigned long hmm_pfns[], pmd_t pmd); #endif /* CONFIG_TRANSPARENT_HUGEPAGE */

-static inline bool hmm_is_device_private_entry(struct hmm_range *range,

• swp_entry_t entry)
  

-{

• return is_device_private_entry(entry) &&

• pfn_swap_entry_to_page(entry)->pgmap->owner ==
  

• range->dev_private_owner;
  

-}

static inline unsigned long pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte) { @@ -252,10 +244,12 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, swp_entry_t entry = pte_to_swp_entry(pte);

/*

•  * Never fault in device private pages, but just report
  

•  * the PFN even if not present.
  

•  * Don't fault in device private pages owned by the caller,
  

•  * just report the PFN.
  

  */

• if (hmm_is_device_private_entry(range, entry)) {
  

• if (is_device_private_entry(entry) &&
  

•     pfn_swap_entry_to_page(entry)->pgmap->owner ==
  

•     range->dev_private_owner) {
  cpu_flags = HMM_PFN_VALID;
  if (is_writable_device_private_entry(entry))
  	cpu_flags |= HMM_PFN_WRITE;
  

@@ -273,6 +267,9 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, if (!non_swap_entry(entry)) goto fault;

• if (is_device_private_entry(entry))
  

• 	goto fault;
  

• if (is_device_exclusive_entry(entry)) goto fault;