linux-kernel - Re: [PATCH v2,04/21] v4l: add documentation for secure memory flag

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Date:   Sat, 11 Nov 2023 20:06:15 +0100
From:   Pavel Machek <pavel@....cz>
To:     Yunfei Dong <yunfei.dong@...iatek.com>
Cc:     Jeffrey Kardatzke <jkardatzke@...gle.com>,
        "T . J . Mercier" <tjmercier@...gle.com>,
        John Stultz <jstultz@...gle.com>,
        Yong Wu <yong.wu@...iatek.com>,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>,
        Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        Nathan Hebert <nhebert@...omium.org>,
        Chen-Yu Tsai <wenst@...omium.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Fritz Koenig <frkoenig@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Steve Cho <stevecho@...omium.org>, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v2,04/21] v4l: add documentation for secure memory flag

Hi!

> From: Jeffrey Kardatzke <jkardatzke@...gle.com>
> 
> Adds documentation for V4L2_MEMORY_FLAG_SECURE.

> --- a/Documentation/userspace-api/media/v4l/buffer.rst
> +++ b/Documentation/userspace-api/media/v4l/buffer.rst
> @@ -696,7 +696,7 @@ enum v4l2_memory
>  
>  .. _memory-flags:
>  
> -Memory Consistency Flags
> +Memory Flags
>  ------------------------
>  
>  .. raw:: latex
> @@ -728,6 +728,12 @@ Memory Consistency Flags
>  	only if the buffer is used for :ref:`memory mapping <mmap>` I/O and the
>  	queue reports the :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS
>  	<V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS>` capability.
> +    * .. _`V4L2-MEMORY-FLAG-SECURE`:
> +
> +      - ``V4L2_MEMORY_FLAG_SECURE``
> +      - 0x00000002
> +      - DMA bufs passed into the queue will be validated to ensure they were
> +	allocated from a secure dma-heap.

Could we get some more information somewhere? Why would userspace want
to work with "secure" DMA heaps? How exactly are they different from
others? What attacks are these secure against? What is goal of all
this? DRM?

BR,
								Pavel
-- 
People of Russia, stop Putin before his war on Ukraine escalates.

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