[PATCH v2 4/4] fixup! drm/gpusvm: use hmm_range_fault_unlocked_timeout() for range faults

[Stanislav Kinsburskii]

The timeout passed to hmm_range_fault_unlocked_timeout() is a relative
retry budget for HMM's internal mmu-notifier retry loop. drm_gpusvm was
still keeping an absolute deadline around the outer driver retry logic
and passing the remaining time into HMM.

Pass HMM_RANGE_DEFAULT_TIMEOUT directly to
hmm_range_fault_unlocked_timeout() on each HMM fault attempt instead.
If HMM succeeds but the later drm_gpusvm-side mmu_interval_read_retry()
check observes an invalidation, retry with a fresh HMM retry budget.

This keeps the timeout focused on repeated notifier retries inside HMM,
while avoiding an outer deadline that also accounts unrelated driver-side
work after HMM has made progress.

Signed-off-by: Stanislav Kinsburskii <skinsburskii@xxxxxxxxx>
---
 drivers/gpu/drm/drm_gpusvm.c |   21 ++++++---------------
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
index b8f2dd9982f5..76e8a0028c7f 100644
--- a/drivers/gpu/drm/drm_gpusvm.c
+++ b/drivers/gpu/drm/drm_gpusvm.c
@@ -852,8 +852,7 @@ enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,
 		.end = end,
 		.dev_private_owner = dev_private_owner,
 	};
-	unsigned long timeout =
-		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+	unsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 	enum drm_gpusvm_scan_result state = DRM_GPUSVM_SCAN_UNPOPULATED, new_state;
 	unsigned long *pfns;
 	unsigned long npages = npages_in_range(start, end);
@@ -867,8 +866,7 @@ enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,
 	hmm_range.hmm_pfns = pfns;
 
 retry:
-	err = hmm_range_fault_unlocked_timeout(&hmm_range,
-					       max(timeout - jiffies, 1L));
+	err = hmm_range_fault_unlocked_timeout(&hmm_range, timeout);
 	if (err)
 		goto err_free;
 
@@ -1459,8 +1457,7 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
 		.dev_private_owner = ctx->device_private_page_owner,
 	};
 	void *zdd;
-	unsigned long timeout =
-		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+	unsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 	unsigned long i, j;
 	unsigned long npages = npages_in_range(pages_start, pages_end);
 	unsigned long num_dma_mapped;
@@ -1478,9 +1475,6 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
 		return -EINVAL;
 
 retry:
-	if (time_after(jiffies, timeout))
-		return -EBUSY;
-
 	hmm_range.notifier_seq = mmu_interval_read_begin(notifier);
 	if (drm_gpusvm_pages_valid_unlocked(gpusvm, svm_pages))
 		goto set_seqno;
@@ -1495,8 +1489,7 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
 	}
 
 	hmm_range.hmm_pfns = pfns;
-	err = hmm_range_fault_unlocked_timeout(&hmm_range,
-				max_t(long, timeout - jiffies, 1));
+	err = hmm_range_fault_unlocked_timeout(&hmm_range, timeout);
 	mmput(mm);
 	if (err)
 		goto err_free;
@@ -1718,8 +1711,7 @@ int drm_gpusvm_range_evict(struct drm_gpusvm *gpusvm,
 		.end = drm_gpusvm_range_end(range),
 		.dev_private_owner = NULL,
 	};
-	unsigned long timeout =
-		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
+	unsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 	unsigned long *pfns;
 	unsigned long npages = npages_in_range(drm_gpusvm_range_start(range),
 					       drm_gpusvm_range_end(range));
@@ -1734,8 +1726,7 @@ int drm_gpusvm_range_evict(struct drm_gpusvm *gpusvm,
 		return -ENOMEM;
 
 	hmm_range.hmm_pfns = pfns;
-	err = hmm_range_fault_unlocked_timeout(&hmm_range,
-				max_t(long, timeout - jiffies, 1));
+	err = hmm_range_fault_unlocked_timeout(&hmm_range, timeout);
 
 	kvfree(pfns);
 	mmput(mm);