Re: [PATCH V2 10/14] DMA: Add dma_map_decrypted/dma_unmap_encrypted() function

[Tianyu Lan <ltykernel@xxxxxxxxx>]

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@xxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxx>
> ---
>   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);
> +}