linux-kernel - Re: [PATCH 5/9] drm/xen-front: Implement handling of shared display buffers

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Message-ID: <11ce6c96-1739-435c-4b6f-c9f5d02a2905@oracle.com>
Date:   Thu, 22 Feb 2018 19:25:18 -0500
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Oleksandr Andrushchenko <andr2000@...il.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, airlied@...ux.ie,
        daniel.vetter@...el.com, seanpaul@...omium.org,
        gustavo@...ovan.org, jgross@...e.com, konrad.wilk@...cle.com
Cc:     Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
Subject: Re: [PATCH 5/9] drm/xen-front: Implement handling of shared display
 buffers

On 02/21/2018 03:03 AM, Oleksandr Andrushchenko wrote:
>  
>  static int __init xen_drv_init(void)
>  {
> +	/* At the moment we only support case with XEN_PAGE_SIZE == PAGE_SIZE */
> +	BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);


Why BUILD_BUG_ON? This should simply not load if page sizes are different.

 



> +	ret = gnttab_map_refs(map_ops, NULL, buf->pages, buf->num_pages);
> +	BUG_ON(ret);


We should try not to BUG*(). There are a few in this patch (and possibly
others) that I think can be avoided.





> +
> +static int alloc_storage(struct xen_drm_front_shbuf *buf)
> +{
> +	if (buf->sgt) {
> +		buf->pages = kvmalloc_array(buf->num_pages,
> +				sizeof(struct page *), GFP_KERNEL);
> +		if (!buf->pages)
> +			return -ENOMEM;
> +
> +		if (drm_prime_sg_to_page_addr_arrays(buf->sgt, buf->pages,
> +				NULL, buf->num_pages) < 0)
> +			return -EINVAL;
> +	}
> +
> +	buf->grefs = kcalloc(buf->num_grefs, sizeof(*buf->grefs), GFP_KERNEL);
> +	if (!buf->grefs)
> +		return -ENOMEM;
> +
> +	buf->directory = kcalloc(get_num_pages_dir(buf), PAGE_SIZE, GFP_KERNEL);
> +	if (!buf->directory)
> +		return -ENOMEM;

You need to clean up on errors.

-boris

> +
> +	return 0;
> +}