Re: [PATCH 8/9] drm/xen-front: Implement GEM operations

From: Boris Ostrovsky
Date: Fri Feb 23 2018 - 10:26:39 EST


On 02/21/2018 03:03 AM, Oleksandr Andrushchenko wrote:
> +static struct xen_gem_object *gem_create(struct drm_device *dev, size_t size)
> +{
> + struct xen_drm_front_drm_info *drm_info = dev->dev_private;
> + struct xen_gem_object *xen_obj;
> + int ret;
> +
> + size = round_up(size, PAGE_SIZE);
> + xen_obj = gem_create_obj(dev, size);
> + if (IS_ERR_OR_NULL(xen_obj))
> + return xen_obj;
> +
> + if (drm_info->cfg->be_alloc) {
> + /*
> + * backend will allocate space for this buffer, so
> + * only allocate array of pointers to pages
> + */
> + xen_obj->be_alloc = true;

If be_alloc is a flag (which I am not sure about) --- should it be set
to true *after* you've successfully allocated your things?

> + ret = gem_alloc_pages_array(xen_obj, size);
> + if (ret < 0) {
> + gem_free_pages_array(xen_obj);
> + goto fail;
> + }
> +
> + ret = alloc_xenballooned_pages(xen_obj->num_pages,
> + xen_obj->pages);

Why are you allocating balloon pages?

-boris

> + if (ret < 0) {
> + DRM_ERROR("Cannot allocate %zu ballooned pages: %d\n",
> + xen_obj->num_pages, ret);
> + goto fail;
> + }
> +
> + return xen_obj;
> + }
> + /*
> + * need to allocate backing pages now, so we can share those
> + * with the backend
> + */
> + xen_obj->num_pages = DIV_ROUND_UP(size, PAGE_SIZE);
> + xen_obj->pages = drm_gem_get_pages(&xen_obj->base);
> + if (IS_ERR_OR_NULL(xen_obj->pages)) {
> + ret = PTR_ERR(xen_obj->pages);
> + xen_obj->pages = NULL;
> + goto fail;
> + }
> +
> + return xen_obj;
> +
> +fail:
> + DRM_ERROR("Failed to allocate buffer with size %zu\n", size);
> + return ERR_PTR(ret);
> +}
> +
>