drm/nouveau: make use of the GPUVM's shared dma-resv

DRM GEM objects private to a single GPUVM can use a shared dma-resv.
Make use of the shared dma-resv of GPUVM rather than a driver specific
one.

The shared dma-resv originates from a "root" GEM object serving as
container for the dma-resv to make it compatible with drm_exec.

In order to make sure the object proving the shared dma-resv can't be
freed up before the objects making use of it, let every such GEM object
take a reference on it.
Reviewed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231108001259.15123-7-dakr@redhat.com

drivers/gpu/drm/nouveau/nouveau_bo.c

@@ -148,10 +148,17 @@ nouveau_bo_del_ttm(struct ttm_buffer_object *bo)
 	 * If nouveau_bo_new() allocated this buffer, the GEM object was never
 	 * initialized, so don't attempt to release it.
 	 */
-	if (bo->base.dev)
+	if (bo->base.dev) {
+		/* Gem objects not being shared with other VMs get their
+		 * dma_resv from a root GEM object.
+		 */
+		if (nvbo->no_share)
+			drm_gem_object_put(nvbo->r_obj);
+
 		drm_gem_object_release(&bo->base);
-	else
+	} else {
 		dma_resv_fini(&bo->base._resv);
+	}
 
 	kfree(nvbo);
 }

drivers/gpu/drm/nouveau/nouveau_bo.h

@@ -26,6 +26,11 @@ struct nouveau_bo {
 	struct list_head entry;
 	int pbbo_index;
 	bool validate_mapped;
+
+	/* Root GEM object we derive the dma_resv of in case this BO is not
+	 * shared between VMs.
+	 */
+	struct drm_gem_object *r_obj;
 	bool no_share;
 
 	/* GPU address space is independent of CPU word size */

drivers/gpu/drm/nouveau/nouveau_gem.c

@@ -111,7 +111,8 @@ nouveau_gem_object_open(struct drm_gem_object *gem, struct drm_file *file_priv)
 	if (vmm->vmm.object.oclass < NVIF_CLASS_VMM_NV50)
 		return 0;
 
-	if (nvbo->no_share && uvmm && &uvmm->resv != nvbo->bo.base.resv)
+	if (nvbo->no_share && uvmm &&
+	    drm_gpuvm_resv(&uvmm->base) != nvbo->bo.base.resv)
 		return -EPERM;
 
 	ret = ttm_bo_reserve(&nvbo->bo, false, false, NULL);
@@ -245,7 +246,7 @@ nouveau_gem_new(struct nouveau_cli *cli, u64 size, int align, uint32_t domain,
 		if (unlikely(!uvmm))
 			return -EINVAL;
 
-		resv = &uvmm->resv;
+		resv = drm_gpuvm_resv(&uvmm->base);
 	}
 
 	if (!(domain & (NOUVEAU_GEM_DOMAIN_VRAM | NOUVEAU_GEM_DOMAIN_GART)))
@@ -288,6 +289,11 @@ nouveau_gem_new(struct nouveau_cli *cli, u64 size, int align, uint32_t domain,
 	if (drm->client.device.info.family >= NV_DEVICE_INFO_V0_TESLA)
 		nvbo->valid_domains &= domain;
 
+	if (nvbo->no_share) {
+		nvbo->r_obj = drm_gpuvm_resv_obj(&uvmm->base);
+		drm_gem_object_get(nvbo->r_obj);
+	}
+
 	*pnvbo = nvbo;
 	return 0;
 }

drivers/gpu/drm/nouveau/nouveau_uvmm.c

@@ -1802,7 +1802,6 @@ nouveau_uvmm_init(struct nouveau_uvmm *uvmm, struct nouveau_cli *cli,
 	int ret;
 
 	mutex_init(&uvmm->mutex);
-	dma_resv_init(&uvmm->resv);
 	mt_init_flags(&uvmm->region_mt, MT_FLAGS_LOCK_EXTERN);
 	mt_set_external_lock(&uvmm->region_mt, &uvmm->mutex);
 
@@ -1842,14 +1841,14 @@ nouveau_uvmm_init(struct nouveau_uvmm *uvmm, struct nouveau_cli *cli,
 			    kernel_managed_addr, kernel_managed_size,
 			    NULL, 0, &cli->uvmm.vmm.vmm);
 	if (ret)
-		goto out_free_gpuva_mgr;
+		goto out_gpuvm_fini;
 
 	cli->uvmm.vmm.cli = cli;
 	mutex_unlock(&cli->mutex);
 
 	return 0;
 
-out_free_gpuva_mgr:
+out_gpuvm_fini:
 	drm_gpuvm_destroy(&uvmm->base);
 out_unlock:
 	mutex_unlock(&cli->mutex);
@@ -1907,6 +1906,4 @@ nouveau_uvmm_fini(struct nouveau_uvmm *uvmm)
 	nouveau_vmm_fini(&uvmm->vmm);
 	drm_gpuvm_destroy(&uvmm->base);
 	mutex_unlock(&cli->mutex);
-
-	dma_resv_fini(&uvmm->resv);
 }

drivers/gpu/drm/nouveau/nouveau_uvmm.h

@@ -12,7 +12,6 @@ struct nouveau_uvmm {
 	struct nouveau_vmm vmm;
 	struct maple_tree region_mt;
 	struct mutex mutex;
-	struct dma_resv resv;
 
 	bool disabled;
 };