drm/amdgpu: revert "rework reserved VMID handling" v2

This reverts commit e44a0fe630c58b0a87d8281f5c1077a3479e5fce.

Initially we used VMID reservation to enforce isolation between
processes. That has now been replaced by proper fence handling.

Both OpenGL, RADV and ROCm developers requested a way to reserve a VMID
for SPM, so restore that approach by reverting back to only allowing a
single process to use the reserved VMID.

Only compile tested for now.

v2: use -ENOENT instead of -EINVAL if VMID is not available

Signed-off-by: Christian König <[e-mail]>
Acked-by: Alex Deucher <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c

···
 {
 	struct amdgpu_device *adev = ring->adev;
 	unsigned vmhub = ring->vm_hub;
-	struct amdgpu_vmid_mgr *id_mgr = &adev->vm_manager.id_mgr[vmhub];
 	uint64_t fence_context = adev->fence_context + ring->idx;
 	bool needs_flush = vm->use_cpu_for_update;
 	uint64_t updates = amdgpu_vm_tlb_seq(vm);
 	int r;
 
-	*id = id_mgr->reserved;
+	*id = vm->reserved_vmid[vmhub];
 	if ((*id)->owner != vm->immediate.fence_context ||
 	    !amdgpu_vmid_compatible(*id, job) ||
 	    (*id)->flushed_updates < updates ||
···
 	return vm->reserved_vmid[vmhub];
 }
 
-int amdgpu_vmid_alloc_reserved(struct amdgpu_device *adev,
+/*
+ * amdgpu_vmid_alloc_reserved - reserve a specific VMID for this vm
+ * @adev: amdgpu device structure
+ * @vm: the VM to reserve an ID for
+ * @vmhub: the VMHUB which should be used
+ *
+ * Mostly used to have a reserved VMID for debugging and SPM.
+ *
+ * Returns: 0 for success, -ENOENT if an ID is already reserved.
+ */
+int amdgpu_vmid_alloc_reserved(struct amdgpu_device *adev, struct amdgpu_vm *vm,
 			       unsigned vmhub)
 {
 	struct amdgpu_vmid_mgr *id_mgr = &adev->vm_manager.id_mgr[vmhub];
+	struct amdgpu_vmid *id;
+	int r = 0;
 
 	mutex_lock(&id_mgr->lock);
-
-	++id_mgr->reserved_use_count;
-	if (!id_mgr->reserved) {
-		struct amdgpu_vmid *id;
-
-		id = list_first_entry(&id_mgr->ids_lru, struct amdgpu_vmid,
-				      list);
-		/* Remove from normal round robin handling */
-		list_del_init(&id->list);
-		id_mgr->reserved = id;
+	if (vm->reserved_vmid[vmhub])
+		goto unlock;
+	if (id_mgr->reserved_vmid) {
+		r = -ENOENT;
+		goto unlock;
 	}
-
+	/* Remove from normal round robin handling */
+	id = list_first_entry(&id_mgr->ids_lru, struct amdgpu_vmid, list);
+	list_del_init(&id->list);
+	vm->reserved_vmid[vmhub] = id;
+	id_mgr->reserved_vmid = true;
 	mutex_unlock(&id_mgr->lock);
+
 	return 0;
+unlock:
+	mutex_unlock(&id_mgr->lock);
+	return r;
 }
 
-void amdgpu_vmid_free_reserved(struct amdgpu_device *adev,
+/*
+ * amdgpu_vmid_free_reserved - free up a reserved VMID again
+ * @adev: amdgpu device structure
+ * @vm: the VM with the reserved ID
+ * @vmhub: the VMHUB which should be used
+ */
+void amdgpu_vmid_free_reserved(struct amdgpu_device *adev, struct amdgpu_vm *vm,
 			       unsigned vmhub)
 {
 	struct amdgpu_vmid_mgr *id_mgr = &adev->vm_manager.id_mgr[vmhub];
 
 	mutex_lock(&id_mgr->lock);
-	if (!--id_mgr->reserved_use_count) {
-		/* give the reserved ID back to normal round robin */
-		list_add(&id_mgr->reserved->list, &id_mgr->ids_lru);
-		id_mgr->reserved = NULL;
+	if (vm->reserved_vmid[vmhub]) {
+		list_add(&vm->reserved_vmid[vmhub]->list,
+			&id_mgr->ids_lru);
+		vm->reserved_vmid[vmhub] = NULL;
+		id_mgr->reserved_vmid = false;
 	}
-
 	mutex_unlock(&id_mgr->lock);
 }
 
···
 
 		mutex_init(&id_mgr->lock);
 		INIT_LIST_HEAD(&id_mgr->ids_lru);
-		id_mgr->reserved_use_count = 0;
 
 		/* for GC <10, SDMA uses MMHUB so use first_kfd_vmid for both GC and MM */
 		if (amdgpu_ip_version(adev, GC_HWIP, 0) < IP_VERSION(10, 0, 0))

drivers/gpu/drm/amd/amdgpu/amdgpu_ids.h

···
 	unsigned		num_ids;
 	struct list_head	ids_lru;
 	struct amdgpu_vmid	ids[AMDGPU_NUM_VMID];
-	struct amdgpu_vmid	*reserved;
-	unsigned int		reserved_use_count;
+	bool			reserved_vmid;
 };
 
 int amdgpu_pasid_alloc(unsigned int bits);
···
 bool amdgpu_vmid_had_gpu_reset(struct amdgpu_device *adev,
 			       struct amdgpu_vmid *id);
 bool amdgpu_vmid_uses_reserved(struct amdgpu_vm *vm, unsigned int vmhub);
-int amdgpu_vmid_alloc_reserved(struct amdgpu_device *adev,
-				unsigned vmhub);
-void amdgpu_vmid_free_reserved(struct amdgpu_device *adev,
-				unsigned vmhub);
+int amdgpu_vmid_alloc_reserved(struct amdgpu_device *adev, struct amdgpu_vm *vm,
+			       unsigned vmhub);
+void amdgpu_vmid_free_reserved(struct amdgpu_device *adev, struct amdgpu_vm *vm,
+			       unsigned vmhub);
 int amdgpu_vmid_grab(struct amdgpu_vm *vm, struct amdgpu_ring *ring,
 		     struct amdgpu_job *job, struct dma_fence **fence);
 void amdgpu_vmid_reset(struct amdgpu_device *adev, unsigned vmhub,

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c

···
 	dma_fence_put(vm->last_update);
 
 	for (i = 0; i < AMDGPU_MAX_VMHUBS; i++) {
-		if (vm->reserved_vmid[i]) {
-			amdgpu_vmid_free_reserved(adev, i);
-			vm->reserved_vmid[i] = false;
-		}
+		amdgpu_vmid_free_reserved(adev, vm, i);
 	}
 
 	ttm_lru_bulk_move_fini(&adev->mman.bdev, &vm->lru_bulk_move);
···
 	union drm_amdgpu_vm *args = data;
 	struct amdgpu_device *adev = drm_to_adev(dev);
 	struct amdgpu_fpriv *fpriv = filp->driver_priv;
+	struct amdgpu_vm *vm = &fpriv->vm;
 
 	/* No valid flags defined yet */
 	if (args->in.flags)
···
 	switch (args->in.op) {
 	case AMDGPU_VM_OP_RESERVE_VMID:
 		/* We only have requirement to reserve vmid from gfxhub */
-		if (!fpriv->vm.reserved_vmid[AMDGPU_GFXHUB(0)]) {
-			amdgpu_vmid_alloc_reserved(adev, AMDGPU_GFXHUB(0));
-			fpriv->vm.reserved_vmid[AMDGPU_GFXHUB(0)] = true;
-		}
-
+		amdgpu_vmid_alloc_reserved(adev, vm, AMDGPU_GFXHUB(0));
 		break;
 	case AMDGPU_VM_OP_UNRESERVE_VMID:
-		if (fpriv->vm.reserved_vmid[AMDGPU_GFXHUB(0)]) {
-			amdgpu_vmid_free_reserved(adev, AMDGPU_GFXHUB(0));
-			fpriv->vm.reserved_vmid[AMDGPU_GFXHUB(0)] = false;
-		}
+		amdgpu_vmid_free_reserved(adev, vm, AMDGPU_GFXHUB(0));
 		break;
 	default:
 		return -EINVAL;

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h

···
 	struct dma_fence	*last_unlocked;
 
 	unsigned int		pasid;
-	bool			reserved_vmid[AMDGPU_MAX_VMHUBS];
+	struct amdgpu_vmid	*reserved_vmid[AMDGPU_MAX_VMHUBS];
 
 	/* Flag to indicate if VM tables are updated by CPU or GPU (SDMA) */
 	bool					use_cpu_for_update;