[PATCH v2] nouveau: fix page fault on device private memory

[Ralph Campbell]

If system memory is migrated to device private memory and no GPU MMU
page table entry exists, the GPU will fault and call hmm_range_fault()
to get the PFN for the page. Since the .dev_private_owner pointer in
struct hmm_range is not set, hmm_range_fault returns an error which
results in the GPU program stopping with a fatal fault.
Fix this by setting .dev_private_owner appropriately.

Fixes: 08ddddda667b ("mm/hmm: check the device private page owner in hmm_range_fault()")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
---

This is based on Linux-5.8.0-rc2 and is for Ben Skeggs nouveau tree.
It doesn't depend on any of the other nouveau/HMM changes I have
recently posted.

Resending to include stable@xxxxxxxx and adding Jason's reviewed-by.

 drivers/gpu/drm/nouveau/nouveau_svm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
index ba9f9359c30e..6586d9d39874 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
@@ -562,6 +562,7 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm,
 		.end = notifier->notifier.interval_tree.last + 1,
 		.pfn_flags_mask = HMM_PFN_REQ_FAULT | HMM_PFN_REQ_WRITE,
 		.hmm_pfns = hmm_pfns,
+		.dev_private_owner = drm->dev,
 	};
 	struct mm_struct *mm = notifier->notifier.mm;
 	int ret;
-- 
2.20.1