drm/amdgpu: Unlocked unmap only clear page table leaves

SVM migration unmap pages from GPU and then update mapping to GPU to
recover page fault. Currently unmap clears the PDE entry for range
length >= huge page and free PTB bo, update mapping to alloc new PT bo.
There is race bug that the freed entry bo maybe still on the pt_free
list, reused when updating mapping and then freed, leave invalid PDE
entry and cause GPU page fault.

By setting the update to clear only one PDE entry or clear PTB, to
avoid unmap to free PTE bo. This fixes the race bug and improve the
unmap and map to GPU performance. Update mapping to huge page will
still free the PTB bo.

With this change, the vm->pt_freed list and work is not needed. Add
WARN_ON(unlocked) in amdgpu_vm_pt_free_dfs to catch if unmap to free the
PTB.

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 13 insertions, 30 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
index b0bf21682115..30022123b0bf 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
@@ -547,27 +547,6 @@ static void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry)
 	amdgpu_bo_unref(&entry->bo);
 }
 
-void amdgpu_vm_pt_free_work(struct work_struct *work)
-{
-	struct amdgpu_vm_bo_base *entry, *next;
-	struct amdgpu_vm *vm;
-	LIST_HEAD(pt_freed);
-
-	vm = container_of(work, struct amdgpu_vm, pt_free_work);
-
-	spin_lock(&vm->status_lock);
-	list_splice_init(&vm->pt_freed, &pt_freed);
-	spin_unlock(&vm->status_lock);
-
-	/* flush_work in amdgpu_vm_fini ensure vm->root.bo is valid. */
-	amdgpu_bo_reserve(vm->root.bo, true);
-
-	list_for_each_entry_safe(entry, next, &pt_freed, vm_status)
-		amdgpu_vm_pt_free(entry);
-
-	amdgpu_bo_unreserve(vm->root.bo);
-}
-
 /**
  * amdgpu_vm_pt_free_list - free PD/PT levels
  *
@@ -580,19 +559,15 @@ void amdgpu_vm_pt_free_list(struct amdgpu_device *adev,
 			    struct amdgpu_vm_update_params *params)
 {
 	struct amdgpu_vm_bo_base *entry, *next;
-	struct amdgpu_vm *vm = params->vm;
 	bool unlocked = params->unlocked;
 
 	if (list_empty(&params->tlb_flush_waitlist))
 		return;
 
-	if (unlocked) {
-		spin_lock(&vm->status_lock);
-		list_splice_init(&params->tlb_flush_waitlist, &vm->pt_freed);
-		spin_unlock(&vm->status_lock);
-		schedule_work(&vm->pt_free_work);
-		return;
-	}
+	/*
+	 * unlocked unmap clear page table leaves, warning to free the page entry.
+	 */
+	WARN_ON(unlocked);
 
 	list_for_each_entry_safe(entry, next, &params->tlb_flush_waitlist, vm_status)
 		amdgpu_vm_pt_free(entry);
@@ -900,7 +875,15 @@ int amdgpu_vm_ptes_update(struct amdgpu_vm_update_params *params,
 		incr = (uint64_t)AMDGPU_GPU_PAGE_SIZE << shift;
 		mask = amdgpu_vm_pt_entries_mask(adev, cursor.level);
 		pe_start = ((cursor.pfn >> shift) & mask) * 8;
-		entry_end = ((uint64_t)mask + 1) << shift;
+
+		if (cursor.level < AMDGPU_VM_PTB && params->unlocked)
+			/*
+			 * MMU notifier callback unlocked unmap huge page, leave is PDE entry,
+			 * only clear one entry. Next entry search again for PDE or PTE leave.
+			 */
+			entry_end = 1ULL << shift;
+		else
+			entry_end = ((uint64_t)mask + 1) << shift;
 		entry_end += cursor.pfn & ~(entry_end - 1);
 		entry_end = min(entry_end, end);