Re: [PATCH] drm/amdkfd: Use partial mapping in GPU page fault recovery

[Philip Yang]

On 2023-10-19 10:24, Xiaogang.Chen wrote:

From: Xiaogang Chen <xiaogang.c...@amd.com>

After partial migration to recover GPU page fault this patch does GPU vm
space mapping for same page range that got migrated instead of mapping all
pages of svm range in which the page fault happened.

Signed-off-by: Xiaogang Chen<xiaogang.c...@amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 33 +++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 54af7a2b29f8..81dbcc8a4ccc 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -1619,6 +1619,7 @@ static void *kfd_svm_page_owner(struct kfd_process *p, int32_t gpuidx)
  * 5. Release page table (and SVM BO) reservation
  */
 static int svm_range_validate_and_map(struct mm_struct *mm,
+				      unsigned long map_start, unsigned long map_last,
 				      struct svm_range *prange, int32_t gpuidx,
 				      bool intr, bool wait, bool flush_tlb)
 {
@@ -1630,6 +1631,12 @@ static int svm_range_validate_and_map(struct mm_struct *mm,
 	int32_t idx;
 	int r = 0;
 
+	if (map_start < prange->start || map_last > prange->last) {

This is not needed, as this case should never happen, and you also use max/min to limit map_start, map_last below.

+		pr_debug("range [0x%lx 0x%lx] out prange [0x%lx 0x%lx]\n",
+				 map_start, map_last, prange->start, prange->last);
+		return -EFAULT;
+	}
+
 	ctx = kzalloc(sizeof(struct svm_validate_context), GFP_KERNEL);
 	if (!ctx)
 		return -ENOMEM;
@@ -1747,9 +1754,16 @@ static int svm_range_validate_and_map(struct mm_struct *mm,
 			r = -EAGAIN;
 		}
 
-		if (!r)
-			r = svm_range_map_to_gpus(prange, offset, npages, readonly,
-						  ctx->bitmap, wait, flush_tlb);
+		if (!r) {
+			map_start = max(map_start, prange->start + offset);
+			map_last = min(map_last, prange->start + offset + npages);

This should move forward to outside the for loop, otherwise amdgpu_hmm_range_get_pages and svm_range_dma_map still work on the entire prange, and then prange->vram_pages update logic should be changed accordingly.

Regards,

Philip

+			if (map_start <= map_last) {
+				offset = map_start - prange->start;
+				npages = map_last - map_start + 1;
+				r = svm_range_map_to_gpus(prange, offset, npages, readonly,
+							  ctx->bitmap, wait, flush_tlb);
+			}
+		}
 
 		if (!r && next == end)
 			prange->mapped_to_gpu = true;
@@ -1855,8 +1869,8 @@ static void svm_range_restore_work(struct work_struct *work)
 		 */
 		mutex_lock(&prange->migrate_mutex);
 
-		r = svm_range_validate_and_map(mm, prange, MAX_GPU_INSTANCE,
-					       false, true, false);
+		r = svm_range_validate_and_map(mm, prange->start, prange->last, prange,
+					       MAX_GPU_INSTANCE, false, true, false);
 		if (r)
 			pr_debug("failed %d to map 0x%lx to gpus\n", r,
 				 prange->start);
@@ -3069,6 +3083,8 @@ svm_range_restore_pages(struct amdgpu_device *adev, unsigned int pasid,
 	kfd_smi_event_page_fault_start(node, p->lead_thread->pid, addr,
 				       write_fault, timestamp);
 
+	start = prange->start;
+	last = prange->last;
 	if (prange->actual_loc != 0 || best_loc != 0) {
 		migration = true;
 		/* Align migration range start and size to granularity size */
@@ -3102,10 +3118,11 @@ svm_range_restore_pages(struct amdgpu_device *adev, unsigned int pasid,
 		}
 	}
 
-	r = svm_range_validate_and_map(mm, prange, gpuidx, false, false, false);
+	r = svm_range_validate_and_map(mm, start, last, prange, gpuidx, false,
+				       false, false);
 	if (r)
 		pr_debug("failed %d to map svms 0x%p [0x%lx 0x%lx] to gpus\n",
-			 r, svms, prange->start, prange->last);
+			 r, svms, start, last);
 
 	kfd_smi_event_page_fault_end(node, p->lead_thread->pid, addr,
 				     migration);
@@ -3650,7 +3667,7 @@ svm_range_set_attr(struct kfd_process *p, struct mm_struct *mm,
 
 		flush_tlb = !migrated && update_mapping && prange->mapped_to_gpu;
 
-		r = svm_range_validate_and_map(mm, prange, MAX_GPU_INSTANCE,
+		r = svm_range_validate_and_map(mm, prange->start, prange->last, prange, MAX_GPU_INSTANCE,
 					       true, true, flush_tlb);
 		if (r)
 			pr_debug("failed %d to map svm range\n", r);