[PATCH 1/2] drm/amdgpu: Fix the looply call svm_range_restore_pages issue

[Emily Deng]

As the delayed free pt, the wanted freed bo has been reused which will cause
unexpected page fault, and then call svm_range_restore_pages.

Detail as below:
1.It wants to free the pt in follow code, but it is not freed immediately
and used “schedule_work(&vm->pt_free_work);”.

[   92.276838] Call Trace:
[   92.276841]  dump_stack+0x63/0xa0
[   92.276887]  amdgpu_vm_pt_free_list+0xfb/0x120 [amdgpu]
[   92.276932]  amdgpu_vm_update_range+0x69c/0x8e0 [amdgpu]
[   92.276990]  svm_range_unmap_from_gpus+0x112/0x310 [amdgpu]
[   92.277046]  svm_range_cpu_invalidate_pagetables+0x725/0x780 [amdgpu]
[   92.277050]  ? __alloc_pages_nodemask+0x19f/0x3e0
[   92.277051]  mn_itree_invalidate+0x72/0xc0
[   92.277052]  __mmu_notifier_invalidate_range_start+0x48/0x60
[   92.277054]  migrate_vma_collect+0xf6/0x100
[   92.277055]  migrate_vma_setup+0xcf/0x120
[   92.277109]  svm_migrate_ram_to_vram+0x256/0x6b0 [amdgpu]

2.Call svm_range_map_to_gpu->amdgpu_vm_update_range to update the page
table, at this time it will use the same entry bo which is the want free
bo in step1.

3.Then it executes the pt_free_work to free the bo. At this time, the GPU
access memory will cause page fault as pt bo has been freed. And then it will
call svm_range_restore_pages again.

How to fix?
Add a workqueue, and flush the workqueue each time before updating page table.

Signed-off-by: Emily Deng <Emily.Deng at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h       | 1 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c    | 8 ++++++--
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c | 2 +-
 3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 5e55a44f9eef..cfb2916f937d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -1209,6 +1209,7 @@ struct amdgpu_device {
 	struct mutex                    enforce_isolation_mutex;
 
 	struct amdgpu_init_level *init_lvl;
+	struct workqueue_struct *wq;
 };
 
 static inline uint32_t amdgpu_ip_version(const struct amdgpu_device *adev,
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index c9c48b782ec1..b35a7d83a0a4 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -983,6 +983,7 @@ int amdgpu_vm_update_range(struct amdgpu_device *adev, struct amdgpu_vm *vm,
 	 */
 	flush_tlb |= amdgpu_ip_version(adev, GC_HWIP, 0) < IP_VERSION(9, 0, 0);
 
+	flush_workqueue(adev->wq);
 	memset(&params, 0, sizeof(params));
 	params.adev = adev;
 	params.vm = vm;
@@ -2614,7 +2615,7 @@ void amdgpu_vm_fini(struct amdgpu_device *adev, struct amdgpu_vm *vm)
 	amdgpu_amdkfd_gpuvm_destroy_cb(adev, vm);
 
 	flush_work(&vm->pt_free_work);
-
+	cancel_work_sync(&vm->pt_free_work);
 	root = amdgpu_bo_ref(vm->root.bo);
 	amdgpu_bo_reserve(root, true);
 	amdgpu_vm_put_task_info(vm->task_info);
@@ -2716,6 +2717,8 @@ void amdgpu_vm_manager_init(struct amdgpu_device *adev)
 #endif
 
 	xa_init_flags(&adev->vm_manager.pasids, XA_FLAGS_LOCK_IRQ);
+	adev->wq = alloc_workqueue("amdgpu_recycle",
+				   WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 16);
 }
 
 /**
@@ -2729,7 +2732,8 @@ void amdgpu_vm_manager_fini(struct amdgpu_device *adev)
 {
 	WARN_ON(!xa_empty(&adev->vm_manager.pasids));
 	xa_destroy(&adev->vm_manager.pasids);
-
+	flush_workqueue(adev->wq);
+	destroy_workqueue(adev->wq);
 	amdgpu_vmid_mgr_fini(adev);
 }
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
index f78a0434a48f..7543c428873b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
@@ -589,7 +589,7 @@ void amdgpu_vm_pt_free_list(struct amdgpu_device *adev,
 		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);
+		queue_work(adev->wq, &vm->pt_free_work);
 		return;
 	}
 
-- 
2.36.1