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

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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);
+}




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