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

From: Tianyu Lan <[email-masked]>
Date: Wed, 4 Aug 2021 14:45:06 -0400

From: Tianyu Lan <[email-masked]>

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 <[email-masked]>
---
 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);
+}
-- 
2.25.1