linux-kernel - Re: [RFC PATCH] media: vb2: add bidirectional flag in vb2

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20170815095825.dcg64udoj47dqiro@valkosipuli.retiisi.org.uk>
Date:   Tue, 15 Aug 2017 12:58:25 +0300
From:   Sakari Ailus <sakari.ailus@....fi>
To:     Stanimir Varbanov <stanimir.varbanov@...aro.org>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        Pawel Osciak <pawel@...iak.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [RFC PATCH] media: vb2: add bidirectional flag in vb2_queue

On Mon, Aug 14, 2017 at 11:41:55AM +0300, Stanimir Varbanov wrote:
> Hi,
> 
> This RFC patch is intended to give to the drivers a choice to change
> the default behavior of the v4l2-core DMA mapping direction from
> DMA_TO/FROM_DEVICE (depending on the buffer type CAPTURE or OUTPUT)
> to DMA_BIDIRECTIONAL during queue_init time.
> 
> Initially the issue with DMA mapping direction has been found in
> Venus encoder driver where the firmware side of the driver adds few
> lines padding on bottom of the image buffer, and the consequence was
> triggering of IOMMU protection faults. 
> 
> Probably other drivers could also has a benefit of this feature (hint)
> in the future.
> 
> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>

Acked-by: Sakari Ailus <sakari.ailus@...ux.intel.com>

> ---
>  drivers/media/v4l2-core/videobuf2-core.c |  3 +++
>  include/media/videobuf2-core.h           | 11 +++++++++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
> index 14f83cecfa92..17d07fda4cdc 100644
> --- a/drivers/media/v4l2-core/videobuf2-core.c
> +++ b/drivers/media/v4l2-core/videobuf2-core.c
> @@ -200,6 +200,9 @@ static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
>  	int plane;
>  	int ret = -ENOMEM;
>  
> +	if (q->bidirectional)
> +		dma_dir = DMA_BIDIRECTIONAL;
> +
>  	/*
>  	 * Allocate memory for all planes in this buffer
>  	 * NOTE: mmapped areas should be page aligned
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index cb97c224be73..0b6e88e1aa79 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -427,6 +427,16 @@ struct vb2_buf_ops {
>   * @dev:	device to use for the default allocation context if the driver
>   *		doesn't fill in the @alloc_devs array.
>   * @dma_attrs:	DMA attributes to use for the DMA.
> + * @bidirectional: when this flag is set the DMA direction for the buffers of
> + *		this queue will be overridden with DMA_BIDIRECTIONAL direction.
> + *		This is useful in cases where the hardware (firmware) writes to
> + *		a buffer which is mapped as read (DMA_TO_DEVICE), or reads from
> + *		buffer which is mapped for write (DMA_FROM_DEVICE) in order
> + *		to satisfy some internal hardware restrictions or adds a padding
> + *		needed by the processing algorithm. In case the DMA mapping is
> + *		not bidirectional but the hardware (firmware) trying to access
> + *		the buffer (in the opposite direction) this could lead to an
> + *		IOMMU protection faults.
>   * @fileio_read_once:		report EOF after reading the first buffer
>   * @fileio_write_immediately:	queue buffer after each write() call
>   * @allow_zero_bytesused:	allow bytesused == 0 to be passed to the driver
> @@ -495,6 +505,7 @@ struct vb2_queue {
>  	unsigned int			io_modes;
>  	struct device			*dev;
>  	unsigned long			dma_attrs;
> +	unsigned			bidirectional:1;
>  	unsigned			fileio_read_once:1;
>  	unsigned			fileio_write_immediately:1;
>  	unsigned			allow_zero_bytesused:1;
> -- 
> 2.11.0
> 

-- 
Sakari Ailus
e-mail: sakari.ailus@....fi