Re: [PATCH v3 7/8] drm/nouveau: use DRM_GPUVM_RESV_PROTECTED

[Liviu Dudau <liviu.dudau@arm.com>]

On Thu, Oct 01, 2026 at 03:06:31PM -0700, Matthew Brost wrote:
> nouveau creates its drm_gpuvm without DRM_GPUVM_RESV_PROTECTED, so the
> extobj and evicted lists are protected by internal spinlocks. Every
> nouveau path but three already touches them with the VM's resv held:
> drm_gpuvm_exec_lock() and drm_gpuvm_validate() on exec, and TTM moves of
> private BOs, which share the VM's resv. The remaining three are:
> 
>  - nouveau_uvmm_bind_job_submit() adds the vm_bo of a MAP op to the
>    extobj list holding no resv at all. Move that into
>    bind_lock_validate(), which now locks the VM's resv as well.
> 
>  - bind_link_gpuvas() unlinks the GPUVAs of UNMAP and REMAP ops, which
>    can drop the last reference of their vm_bo. It runs within the bind
>    job's drm_exec transaction, which the above makes hold the VM's resv.
> 
>  - nouveau_uvmm_bind_job_cleanup() and nouveau_uvmm_fini() can drop the
>    last reference of a vm_bo holding only the object's resv. Lock the
>    VM's resv along with it, through a new
>    nouveau_uvmm_lock_vm_and_obj().
> 
> The bind job's fence now always lands in the VM's resv, as BOOKKEEP.
> This already happened whenever a bind job mapped a private BO.
> 
> With that the internal spinlocks buy nothing, so set
> DRM_GPUVM_RESV_PROTECTED. This is also what two-pass locking in
> drm_gpuvm requires, which a following patch makes use of.
> 
> Cc: Abhinav Kumar <abhinav.kumar@linux.dev>
> Cc: Alice Ryhl <aliceryhl@google.com>
> Cc: Anna Maniscalco <anna.maniscalco2000@gmail.com>
> Cc: Antonino Maniscalco <antomani103@gmail.com>
> Cc: Boris Brezillon <boris.brezillon@collabora.com>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Cc: David Airlie <airlied@gmail.com>
> Cc: Dmitry Baryshkov <lumag@kernel.org>
> Cc: Jessica Zhang <jesszhan0024@gmail.com>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Liviu Dudau <liviu.dudau@arm.com>
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Marijn Suijten <marijn.suijten@somainline.org>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Randy Dunlap <rdunlap@infradead.org>
> Cc: Rob Clark <robin.clark@oss.qualcomm.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Sean Paul <sean@poorly.run>
> Cc: Shuah Khan <skhan@linuxfoundation.org>
> Cc: Simona Vetter <simona@ffwll.ch>
> Cc: Steven Price <steven.price@arm.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> Assisted-by: LLM
> ---
> v3:
>  - New patch (Danilo)

Bit confused about this. If Danilo contributed this patch should it not carry his S-o-b as well?

Best regards,
Liviu

> ---
>  drivers/gpu/drm/nouveau/nouveau_uvmm.c | 49 ++++++++++++++++++++++----
>  1 file changed, 42 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> index 2026fe6b48c6..dae612e56d91 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> @@ -1187,6 +1187,27 @@ bind_validate_region(struct nouveau_job *job)
>  	return 0;
>  }
>  
> +/*
> + * Lock the VM's common dma-resv together with the one of @obj, as needed to
> + * drop what may be the last reference of a &drm_gpuvm_bo.
> + */
> +static void
> +nouveau_uvmm_lock_vm_and_obj(struct nouveau_uvmm *uvmm, struct drm_exec *exec,
> +			     struct drm_gem_object *obj)
> +{
> +	int ret;
> +
> +	drm_exec_init(exec, DRM_EXEC_IGNORE_DUPLICATES, 2);
> +	drm_exec_until_all_locked(exec) {
> +		ret = drm_exec_lock_obj(exec, drm_gpuvm_resv_obj(&uvmm->base));
> +		if (!ret)
> +			ret = drm_exec_lock_obj(exec, obj);
> +		drm_exec_retry_on_contention(exec);
> +		if (drm_WARN_ON(uvmm->base.drm, ret))
> +			break;
> +	}
> +}
> +
>  static void
>  bind_link_gpuvas(struct bind_job_op *bop)
>  {
> @@ -1224,12 +1245,24 @@ bind_lock_validate(struct nouveau_job *job, struct drm_exec *exec,
>  		   unsigned int num_fences)
>  {
>  	struct nouveau_uvmm_bind_job *bind_job = to_uvmm_bind_job(job);
> +	struct nouveau_uvmm *uvmm = nouveau_cli_uvmm(job->cli);
>  	struct bind_job_op *op;
>  	int ret;
>  
> +	/* The VM's dma-resv protects its extobj and evicted lists, and must be
> +	 * held by bind_link_gpuvas() in case it drops the last reference of a
> +	 * &drm_gpuvm_bo.
> +	 */
> +	ret = drm_gpuvm_prepare_vm(&uvmm->base, exec, num_fences);
> +	if (ret)
> +		return ret;
> +
>  	list_for_each_op(op, &bind_job->ops) {
>  		struct drm_gpuva_op *va_op;
>  
> +		if (op->op == OP_MAP)
> +			drm_gpuvm_bo_extobj_add(op->vm_bo);
> +
>  		if (!op->ops)
>  			continue;
>  
> @@ -1288,8 +1321,6 @@ nouveau_uvmm_bind_job_submit(struct nouveau_job *job,
>  			dma_resv_unlock(obj->resv);
>  			if (IS_ERR(op->vm_bo))
>  				return PTR_ERR(op->vm_bo);
> -
> -			drm_gpuvm_bo_extobj_add(op->vm_bo);
>  		}
>  
>  		ret = bind_validate_op(job, op);
> @@ -1603,9 +1634,11 @@ nouveau_uvmm_bind_job_cleanup(struct nouveau_job *job)
>  			drm_gpuva_ops_free(&uvmm->base, op->ops);
>  
>  		if (!IS_ERR_OR_NULL(op->vm_bo)) {
> -			dma_resv_lock(obj->resv, NULL);
> +			struct drm_exec exec;
> +
> +			nouveau_uvmm_lock_vm_and_obj(uvmm, &exec, obj);
>  			drm_gpuvm_bo_put(op->vm_bo);
> -			dma_resv_unlock(obj->resv);
> +			drm_exec_fini(&exec);
>  		}
>  
>  		if (obj)
> @@ -1941,7 +1974,8 @@ nouveau_uvmm_ioctl_vm_init(struct drm_device *dev,
>  	mt_init_flags(&uvmm->region_mt, MT_FLAGS_LOCK_EXTERN);
>  	mt_set_external_lock(&uvmm->region_mt, &uvmm->mutex);
>  
> -	drm_gpuvm_init(&uvmm->base, cli->name, 0, drm, r_obj,
> +	drm_gpuvm_init(&uvmm->base, cli->name, DRM_GPUVM_RESV_PROTECTED,
> +		       drm, r_obj,
>  		       NOUVEAU_VA_SPACE_START,
>  		       NOUVEAU_VA_SPACE_END,
>  		       init->kernel_managed_addr,
> @@ -1978,6 +2012,7 @@ nouveau_uvmm_fini(struct nouveau_uvmm *uvmm)
>  	struct nouveau_uvma_region *reg;
>  	struct nouveau_cli *cli = uvmm->vmm.cli;
>  	struct drm_gpuva *va, *next;
> +	struct drm_exec exec;
>  
>  	nouveau_uvmm_lock(uvmm);
>  	drm_gpuvm_for_each_va_safe(va, next, &uvmm->base) {
> @@ -1989,9 +2024,9 @@ nouveau_uvmm_fini(struct nouveau_uvmm *uvmm)
>  
>  		drm_gpuva_remove(va);
>  
> -		dma_resv_lock(obj->resv, NULL);
> +		nouveau_uvmm_lock_vm_and_obj(uvmm, &exec, obj);
>  		drm_gpuva_unlink(va);
> -		dma_resv_unlock(obj->resv);
> +		drm_exec_fini(&exec);
>  
>  		nouveau_uvma_unmap(uvma);
>  		nouveau_uvma_vmm_put(uvma);
> -- 
> 2.34.1
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯