drm/amdkfd: Handle queue destroy buffer access race

Add helper function kfd_queue_unreference_buffers to reduce queue buffer
refcount, separate it from release queue buffers.

Because it is circular locking to hold dqm_lock to take vm lock,
kfd_ioctl_destroy_queue should take vm lock, unreference queue buffers
first, but not release queue buffers, to handle error in case failed to
hold vm lock. Then hold dqm_lock to remove queue from queue list and
then release queue buffers.

Restore process worker restore queue hold dqm_lock, will always find
the queue with valid queue buffers.

v2 (Felix):
- renamed kfd_queue_unreference_buffer(s) to kfd_queue_unref_bo_va(s)
- added two FIXME comments for follow up
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Signed-off-by: Felix Kuehling <felix.kuehling@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_chardev.c

@@ -400,6 +400,7 @@ static int kfd_ioctl_create_queue(struct file *filep, struct kfd_process *p,
 	return 0;
 
 err_create_queue:
+	kfd_queue_unref_bo_vas(pdd, &q_properties);
 	kfd_queue_release_buffers(pdd, &q_properties);
 err_acquire_queue_buf:
 err_sdma_engine_id:

drivers/gpu/drm/amd/amdkfd/kfd_priv.h

@@ -1298,9 +1298,12 @@ void print_queue_properties(struct queue_properties *q);
 void print_queue(struct queue *q);
 int kfd_queue_buffer_get(struct amdgpu_vm *vm, void __user *addr, struct amdgpu_bo **pbo,
 			 u64 expected_size);
-void kfd_queue_buffer_put(struct amdgpu_vm *vm, struct amdgpu_bo **bo);
+void kfd_queue_buffer_put(struct amdgpu_bo **bo);
 int kfd_queue_acquire_buffers(struct kfd_process_device *pdd, struct queue_properties *properties);
 int kfd_queue_release_buffers(struct kfd_process_device *pdd, struct queue_properties *properties);
+void kfd_queue_unref_bo_va(struct amdgpu_vm *vm, struct amdgpu_bo **bo);
+int kfd_queue_unref_bo_vas(struct kfd_process_device *pdd,
+			   struct queue_properties *properties);
 void kfd_queue_ctx_save_restore_size(struct kfd_topology_device *dev);
 
 struct mqd_manager *mqd_manager_init_cik(enum KFD_MQD_TYPE type,

drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c

@@ -217,6 +217,7 @@ void pqm_uninit(struct process_queue_manager *pqm)
 	list_for_each_entry_safe(pqn, next, &pqm->queues, process_queue_list) {
 		if (pqn->q) {
 			pdd = kfd_get_process_device_data(pqn->q->device, pqm->process);
+			kfd_queue_unref_bo_vas(pdd, &pqn->q->properties);
 			kfd_queue_release_buffers(pdd, &pqn->q->properties);
 			pqm_clean_queue_resource(pqm, pqn);
 		}
@@ -512,7 +513,7 @@ int pqm_destroy_queue(struct process_queue_manager *pqm, unsigned int qid)
 	}
 
 	if (pqn->q) {
-		retval = kfd_queue_release_buffers(pdd, &pqn->q->properties);
+		retval = kfd_queue_unref_bo_vas(pdd, &pqn->q->properties);
 		if (retval)
 			goto err_destroy_queue;
 
@@ -526,7 +527,7 @@ int pqm_destroy_queue(struct process_queue_manager *pqm, unsigned int qid)
 			if (retval != -ETIME)
 				goto err_destroy_queue;
 		}
-
+		kfd_queue_release_buffers(pdd, &pqn->q->properties);
 		pqm_clean_queue_resource(pqm, pqn);
 		uninit_queue(pqn->q);
 	}
@@ -579,7 +580,8 @@ int pqm_update_queue_properties(struct process_queue_manager *pqm,
 			return -EFAULT;
 		}
 
-		kfd_queue_buffer_put(vm, &pqn->q->properties.ring_bo);
+		kfd_queue_unref_bo_va(vm, &pqn->q->properties.ring_bo);
+		kfd_queue_buffer_put(&pqn->q->properties.ring_bo);
 		amdgpu_bo_unreserve(vm->root.bo);
 
 		pqn->q->properties.ring_bo = p->ring_bo;

drivers/gpu/drm/amd/amdkfd/kfd_queue.c

@@ -224,16 +224,9 @@ int kfd_queue_buffer_get(struct amdgpu_vm *vm, void __user *addr, struct amdgpu_
 	return -EINVAL;
 }
 
-void kfd_queue_buffer_put(struct amdgpu_vm *vm, struct amdgpu_bo **bo)
+/* FIXME: remove this function, just call amdgpu_bo_unref directly */
+void kfd_queue_buffer_put(struct amdgpu_bo **bo)
 {
-	if (*bo) {
-		struct amdgpu_bo_va *bo_va;
-
-		bo_va = amdgpu_vm_bo_find(vm, *bo);
-		if (bo_va)
-			bo_va->queue_refcount--;
-	}
-
 	amdgpu_bo_unref(bo);
 }
 
@@ -327,6 +320,10 @@ int kfd_queue_acquire_buffers(struct kfd_process_device *pdd, struct queue_prope
 out_err_unreserve:
 	amdgpu_bo_unreserve(vm->root.bo);
 out_err_release:
+	/* FIXME: make a _locked version of this that can be called before
+	 * dropping the VM reservation.
+	 */
+	kfd_queue_unref_bo_vas(pdd, properties);
 	kfd_queue_release_buffers(pdd, properties);
 	return err;
 }
@@ -334,22 +331,13 @@ int kfd_queue_acquire_buffers(struct kfd_process_device *pdd, struct queue_prope
 int kfd_queue_release_buffers(struct kfd_process_device *pdd, struct queue_properties *properties)
 {
 	struct kfd_topology_device *topo_dev;
-	struct amdgpu_vm *vm;
 	u32 total_cwsr_size;
-	int err;
 
-	vm = drm_priv_to_vm(pdd->drm_priv);
-	err = amdgpu_bo_reserve(vm->root.bo, false);
-	if (err)
-		return err;
-
-	kfd_queue_buffer_put(vm, &properties->wptr_bo);
-	kfd_queue_buffer_put(vm, &properties->rptr_bo);
-	kfd_queue_buffer_put(vm, &properties->ring_bo);
-	kfd_queue_buffer_put(vm, &properties->eop_buf_bo);
-	kfd_queue_buffer_put(vm, &properties->cwsr_bo);
-
-	amdgpu_bo_unreserve(vm->root.bo);
+	kfd_queue_buffer_put(&properties->wptr_bo);
+	kfd_queue_buffer_put(&properties->rptr_bo);
+	kfd_queue_buffer_put(&properties->ring_bo);
+	kfd_queue_buffer_put(&properties->eop_buf_bo);
+	kfd_queue_buffer_put(&properties->cwsr_bo);
 
 	topo_dev = kfd_topology_device_by_id(pdd->dev->id);
 	if (!topo_dev)
@@ -362,6 +350,38 @@ int kfd_queue_release_buffers(struct kfd_process_device *pdd, struct queue_prope
 	return 0;
 }
 
+void kfd_queue_unref_bo_va(struct amdgpu_vm *vm, struct amdgpu_bo **bo)
+{
+	if (*bo) {
+		struct amdgpu_bo_va *bo_va;
+
+		bo_va = amdgpu_vm_bo_find(vm, *bo);
+		if (bo_va && bo_va->queue_refcount)
+			bo_va->queue_refcount--;
+	}
+}
+
+int kfd_queue_unref_bo_vas(struct kfd_process_device *pdd,
+			   struct queue_properties *properties)
+{
+	struct amdgpu_vm *vm;
+	int err;
+
+	vm = drm_priv_to_vm(pdd->drm_priv);
+	err = amdgpu_bo_reserve(vm->root.bo, false);
+	if (err)
+		return err;
+
+	kfd_queue_unref_bo_va(vm, &properties->wptr_bo);
+	kfd_queue_unref_bo_va(vm, &properties->rptr_bo);
+	kfd_queue_unref_bo_va(vm, &properties->ring_bo);
+	kfd_queue_unref_bo_va(vm, &properties->eop_buf_bo);
+	kfd_queue_unref_bo_va(vm, &properties->cwsr_bo);
+
+	amdgpu_bo_unreserve(vm->root.bo);
+	return 0;
+}
+
 #define SGPR_SIZE_PER_CU	0x4000
 #define LDS_SIZE_PER_CU		0x10000
 #define HWREG_SIZE_PER_CU	0x1000