linux-kernel - Re: [PATCH v5 2/9] scatterlist: Add a flag for the restricted memory

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Date: Thu, 16 May 2024 10:17:13 +0200
From: Christian König <christian.koenig@....com>
To: Yong Wu <yong.wu@...iatek.com>, Rob Herring <robh+dt@...nel.org>,
 Matthias Brugger <matthias.bgg@...il.com>,
 Sumit Semwal <sumit.semwal@...aro.org>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Benjamin Gaignard <benjamin.gaignard@...labora.com>,
 Brian Starkey <Brian.Starkey@....com>, John Stultz <jstultz@...gle.com>,
 tjmercier@...gle.com,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linaro-mm-sig@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org, Robin Murphy <robin.murphy@....com>,
 Vijayanand Jitta <quic_vjitta@...cinc.com>,
 Joakim Bech <joakim.bech@...aro.org>,
 Jeffrey Kardatzke <jkardatzke@...gle.com>, Pavel Machek <pavel@....cz>,
 Simon Ser <contact@...rsion.fr>, Pekka Paalanen <ppaalanen@...il.com>,
 willy@...radead.org, Logan Gunthorpe <logang@...tatee.com>,
 Daniel Vetter <daniel@...ll.ch>, jianjiao.zeng@...iatek.com,
 kuohong.wang@...iatek.com, youlin.pei@...iatek.com
Subject: Re: [PATCH v5 2/9] scatterlist: Add a flag for the restricted memory

Am 15.05.24 um 13:23 schrieb Yong Wu:
> Introduce a FLAG for the restricted memory which means the memory is
> protected by TEE or hypervisor, then it's inaccessiable for kernel.
>
> Currently we don't use sg_dma_unmark_restricted, thus this interface
> has not been added.

Why should that be part of the scatterlist? It doesn't seem to affect 
any of it's functionality.

As far as I can see the scatterlist shouldn't be the transport of this 
kind of information.

Regards,
Christian.

>
> Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> ---
>   include/linux/scatterlist.h | 34 ++++++++++++++++++++++++++++++++++
>   1 file changed, 34 insertions(+)
>
> diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
> index 77df3d7b18a6..a6ad9018eca0 100644
> --- a/include/linux/scatterlist.h
> +++ b/include/linux/scatterlist.h
> @@ -282,6 +282,7 @@ static inline void sg_unmark_end(struct scatterlist *sg)
>   
>   #define SG_DMA_BUS_ADDRESS	(1 << 0)
>   #define SG_DMA_SWIOTLB		(1 << 1)
> +#define SG_DMA_RESTRICTED	(2 << 1)
>   
>   /**
>    * sg_dma_is_bus_address - Return whether a given segment was marked
> @@ -352,6 +353,31 @@ static inline void sg_dma_mark_swiotlb(struct scatterlist *sg)
>   	sg->dma_flags |= SG_DMA_SWIOTLB;
>   }
>   
> +/**
> + * sg_dma_mark_restricted - Mark the scatterlist for restricted buffer.
> + * @sg:		SG entry
> + *
> + * Description:
> + *   Marks a a scatterlist for the restricted buffer that may be inaccessiable
> + *   in kernel if it is protected.
> + */
> +static inline void sg_dma_mark_restricted(struct scatterlist *sg)
> +{
> +	sg->dma_flags |= SG_DMA_RESTRICTED;
> +}
> +
> +/**
> + * sg_dma_is_restricted - Return whether the scatterlist was marked as restricted
> + *                        buffer.
> + * @sg:		SG entry
> + *
> + * Description:
> + *   Returns true if the scatterlist was marked as restricted buffer.
> + */
> +static inline bool sg_dma_is_restricted(struct scatterlist *sg)
> +{
> +	return sg->dma_flags & SG_DMA_RESTRICTED;
> +}
>   #else
>   
>   static inline bool sg_dma_is_bus_address(struct scatterlist *sg)
> @@ -372,6 +398,14 @@ static inline void sg_dma_mark_swiotlb(struct scatterlist *sg)
>   {
>   }
>   
> +static inline bool sg_dma_is_restricted(struct scatterlist *sg)
> +{
> +	return false;
> +}
> +
> +static inline void sg_dma_mark_restrited(struct scatterlist *sg)
> +{
> +}
>   #endif	/* CONFIG_NEED_SG_DMA_FLAGS */
>   
>   /**