[PATCH 1/2] mm/hmm: support automatic NUMA balancing

Kuehling, Felix Felix.Kuehling at amd.com
Fri May 10 19:53:23 UTC 2019

From: Philip Yang <Philip.Yang at amd.com>

While the page is migrating by NUMA balancing, HMM failed to detect this
condition and still return the old page. Application will use the new
page migrated, but driver pass the old page physical address to GPU,
this crash the application later.

Use pte_protnone(pte) to return this condition and then hmm_vma_do_fault
will allocate new page.

Signed-off-by: Philip Yang <Philip.Yang at amd.com>
 mm/hmm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index 75d2ea906efb..b65c27d5c119 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -554,7 +554,7 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk,
 static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte)
-	if (pte_none(pte) || !pte_present(pte))
+	if (pte_none(pte) || !pte_present(pte) || pte_protnone(pte))
 		return 0;
 	return pte_write(pte) ? range->flags[HMM_PFN_VALID] |
 				range->flags[HMM_PFN_WRITE] :

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