Re: [PATCH v2 1/3] drm_gem: add mutex to drm_gem_object.gpuva

[Alice Ryhl <aliceryhl@google.com>]

On Fri, Aug 22, 2025 at 11:52:21AM +0200, Boris Brezillon wrote:
> On Fri, 22 Aug 2025 09:28:24 +0000
> 
> Maybe it's time we start moving some bits of the gpuva field docs next
> to the fields they describe:
> 
> 	/**
> 	 * @gpuva: Fields used by GPUVM to manage mappings pointing to this GEM object.
> 	 */
> 	struct {
> 		/**
> 		 * @gpuva.list: list of GPU VAs attached to this GEM object.
> 		 *
> 		 * Drivers should lock list accesses with the GEMs &dma_resv lock
> 		 * (&drm_gem_object.resv) or &drm_gem_object.gpuva.lock if the
> 		 * list is being updated in places where the resv lock can't be
> 		 * acquired (fence signalling path).
> 		 */
> 		struct list_head list;

This isn't a new issue, but it's somewhat confusing to call it a list of
VAs when it's a list of vm_bos.

> 		/**
> 		 * @gpuva.lock: lock protecting access to &drm_gem_object.gpuva.list
> 		 * when the resv lock can't be used.
> 		 *
> 		 * Should only be used when the VM is being modified in a fence
> 		 * signalling path, otherwise you should use &drm_gem_object.resv to
> 		 * protect accesses to &drm_gem_object.gpuva.list.
> 		 */
> 		struct mutex lock;
> 
> 		...
> 	};
> 

Alice