linux-kernel - Re: [PATCH v2 7/7] drm/virtio: implement userptr: add interval tree

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Message-ID: <810789ec-c034-4bdd-961a-f49c67336e45@collabora.com>
Date: Sun, 30 Mar 2025 14:57:25 +0300
From: Dmitry Osipenko <dmitry.osipenko@...labora.com>
To: Honglei Huang <honglei1.huang@....com>, David Airlie
 <airlied@...hat.com>, Gerd Hoffmann <kraxel@...hat.com>,
 Gurchetan Singh <gurchetansingh@...omium.org>, Chia-I Wu
 <olvaffe@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Simona Vetter <simona@...ll.ch>, Rob Clark <robdclark@...il.com>,
 Huang Rui <ray.huang@....com>
Cc: dri-devel@...ts.freedesktop.org, virtualization@...ts.linux.dev,
 linux-kernel@...r.kernel.org, Demi Marie Obenour <demiobenour@...il.com>
Subject: Re: [PATCH v2 7/7] drm/virtio: implement userptr: add interval tree

If the purpose of this feature is to dedup usrptr BOs of a the single
process/application, can this can be done in userspace?

On 3/21/25 11:00, Honglei Huang wrote:
>  int virtio_gpu_userptr_create(struct virtio_gpu_device *vgdev,
>  			      struct drm_file *file,
>  			      struct virtio_gpu_object_params *params,
> -			      struct virtio_gpu_object **bo_ptr)
> +			      struct virtio_gpu_object **bo_ptr,
> +			      struct drm_virtgpu_resource_create_blob *rc_blob)
>  {
> +	struct virtio_gpu_fpriv *vfpriv = file->driver_priv;
>  	struct virtio_gpu_object_userptr *userptr;
>  	int ret, si;
>  	struct sg_table *sgt;
> @@ -187,6 +290,20 @@ int virtio_gpu_userptr_create(struct virtio_gpu_device *vgdev,
>  		       params->size))
>  		return -EFAULT;
>  
> +	mutex_lock(&vfpriv->userptrs_tree_lock);
> +
> +	userptr = virtio_gpu_userptr_from_addr_range(
> +		vfpriv, params->userptr, params->userptr + params->size - 1UL);

Is it possible that userptr address will be same for two different
processes?

What if userptr->flags mismatch?

> +	if (userptr) {
> +		*bo_ptr = &userptr->base;
> +		rc_blob->res_handle = userptr->base.hw_res_handle;
> +		rc_blob->bo_handle = userptr->bo_handle;

Doesn't BO refcount need to be bumped?

> +		rc_blob->offset = virtio_gpu_userptr_get_offset(
> +			&userptr->base, rc_blob->userptr);
> +		mutex_unlock(&vfpriv->userptrs_tree_lock);
> +		return STATE_RES_EXISTS;

STATE_RES_EXISTS isn't a error code

-- 
Best regards,
Dmitry