netdev - Re: [PATCH V2 10/14] DMA: Add dma_map_decrypted/dma_unmap

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Date:   Thu, 5 Aug 2021 23:56:29 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Christoph Hellwig <hch@....de>
Cc:     iommu@...ts.linux-foundation.org, linux-arch@...r.kernel.org,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
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        michael.h.kelley@...rosoft.com
Subject: Re: [PATCH V2 10/14] DMA: Add dma_map_decrypted/dma_unmap_encrypted()
 function

Hi Christoph:
      Could you have a look at this patch? It adds new API 
dma_map_decrypted() to do memory decrypted and remap. It will
be used in the swiotlb code.

Thanks.

On 8/5/2021 2:45 AM, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@...rosoft.com>
> 
> In Hyper-V Isolation VM with AMD SEV, swiotlb boucne buffer
> needs to be mapped into address space above vTOM and so
> introduce dma_map_decrypted/dma_unmap_encrypted() to map/unmap
> bounce buffer memory. The platform can populate man/unmap callback
> in the dma memory decrypted ops.
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
> ---
>   include/linux/dma-map-ops.h |  9 +++++++++
>   kernel/dma/mapping.c        | 22 ++++++++++++++++++++++
>   2 files changed, 31 insertions(+)
> 
> diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
> index 0d53a96a3d64..01d60a024e45 100644
> --- a/include/linux/dma-map-ops.h
> +++ b/include/linux/dma-map-ops.h
> @@ -71,6 +71,11 @@ struct dma_map_ops {
>   	unsigned long (*get_merge_boundary)(struct device *dev);
>   };
>   
> +struct dma_memory_decrypted_ops {
> +	void *(*map)(void *addr, unsigned long size);
> +	void (*unmap)(void *addr);
> +};
> +
>   #ifdef CONFIG_DMA_OPS
>   #include <asm/dma-mapping.h>
>   
> @@ -374,6 +379,10 @@ static inline void debug_dma_dump_mappings(struct device *dev)
>   }
>   #endif /* CONFIG_DMA_API_DEBUG */
>   
> +void *dma_map_decrypted(void *addr, unsigned long size);
> +int dma_unmap_decrypted(void *addr, unsigned long size);
> +
>   extern const struct dma_map_ops dma_dummy_ops;
> +extern struct dma_memory_decrypted_ops dma_memory_generic_decrypted_ops;
>   
>   #endif /* _LINUX_DMA_MAP_OPS_H */
> diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
> index 2b06a809d0b9..6fb150dc1750 100644
> --- a/kernel/dma/mapping.c
> +++ b/kernel/dma/mapping.c
> @@ -13,11 +13,13 @@
>   #include <linux/of_device.h>
>   #include <linux/slab.h>
>   #include <linux/vmalloc.h>
> +#include <asm/set_memory.h>
>   #include "debug.h"
>   #include "direct.h"
>   
>   bool dma_default_coherent;
>   
> +struct dma_memory_decrypted_ops dma_memory_generic_decrypted_ops;
>   /*
>    * Managed DMA API
>    */
> @@ -736,3 +738,23 @@ unsigned long dma_get_merge_boundary(struct device *dev)
>   	return ops->get_merge_boundary(dev);
>   }
>   EXPORT_SYMBOL_GPL(dma_get_merge_boundary);
> +
> +void *dma_map_decrypted(void *addr, unsigned long size)
> +{
> +	if (set_memory_decrypted((unsigned long)addr,
> +				 size / PAGE_SIZE))
> +		return NULL;
> +
> +	if (dma_memory_generic_decrypted_ops.map)
> +		return dma_memory_generic_decrypted_ops.map(addr, size);
> +	else
> +		return addr;
> +}
> +
> +int dma_unmap_encrypted(void *addr, unsigned long size)
> +{
> +	if (dma_memory_generic_decrypted_ops.unmap)
> +		dma_memory_generic_decrypted_ops.unmap(addr);
> +
> +	return set_memory_encrypted((unsigned long)addr, size / PAGE_SIZE);
> +}
>