Subject: [PATCH v6 11/20] dma-direct: select DMA address encoding from DMA_ATTR_CC_SHARED

From: "Aneesh Kumar K.V (Arm)" <[email-masked]>
Date: Thu, 4 Jun 2026 14:09:50 +0530

Make the dma-direct helpers derive the DMA address encoding from
DMA_ATTR_CC_SHARED instead of implicitly relying on
force_dma_unencrypted() inside phys_to_dma_direct()

Pass an explicit unencrypted/decrypted state into phys_to_dma_direct(),
make the alloc paths return DMA addresses that match the requested buffer
encryption state. Also only call dma_set_decrypted() when
DMA_ATTR_CC_SHARED is actually set.

Tested-by: Jiri Pirko <[email-masked]>
Tested-by: Michael Kelley <[email-masked]>
Tested-by: Mostafa Saleh <[email-masked]>
Signed-off-by: Aneesh Kumar K.V (Arm) <[email-masked]>
---
 kernel/dma/direct.c | 42 +++++++++++++++++++++++++-----------------
 1 file changed, 25 insertions(+), 17 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 9ce4fff6c112..aa3489aa10a0 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -24,11 +24,11 @@
 u64 zone_dma_limit __ro_after_init = DMA_BIT_MASK(24);
 
 static inline dma_addr_t phys_to_dma_direct(struct device *dev,
-		phys_addr_t phys)
+		phys_addr_t phys, bool unencrypted)
 {
-	if (force_dma_unencrypted(dev))
+	if (unencrypted)
 		return phys_to_dma_unencrypted(dev, phys);
-	return phys_to_dma(dev, phys);
+	return phys_to_dma_encrypted(dev, phys);
 }
 
 static inline struct page *dma_direct_to_page(struct device *dev,
@@ -39,8 +39,9 @@ static inline struct page *dma_direct_to_page(struct device *dev,
 
 u64 dma_direct_get_required_mask(struct device *dev)
 {
+	bool require_decrypted = force_dma_unencrypted(dev);
 	phys_addr_t phys = ((phys_addr_t)max_pfn << PAGE_SHIFT) - 1;
-	u64 max_dma = phys_to_dma_direct(dev, phys);
+	u64 max_dma = phys_to_dma_direct(dev, phys, require_decrypted);
 
 	return (1ULL << (fls64(max_dma) - 1)) * 2 - 1;
 }
@@ -69,7 +70,8 @@ static gfp_t dma_direct_optimal_gfp_mask(struct device *dev, u64 *phys_limit)
 
 bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
 {
-	dma_addr_t dma_addr = phys_to_dma_direct(dev, phys);
+	bool require_decrypted = force_dma_unencrypted(dev);
+	dma_addr_t dma_addr = phys_to_dma_direct(dev, phys, require_decrypted);
 
 	if (dma_addr == DMA_MAPPING_ERROR)
 		return false;
@@ -79,17 +81,18 @@ bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
 
 static int dma_set_decrypted(struct device *dev, void *vaddr, size_t size)
 {
-	if (!force_dma_unencrypted(dev))
-		return 0;
-	return set_memory_decrypted((unsigned long)vaddr, PFN_UP(size));
+	int ret;
+
+	ret = set_memory_decrypted((unsigned long)vaddr, PFN_UP(size));
+	if (ret)
+		pr_warn_ratelimited("leaking DMA memory that can't be decrypted\n");
+	return ret;
 }
 
 static int dma_set_encrypted(struct device *dev, void *vaddr, size_t size)
 {
 	int ret;
 
-	if (!force_dma_unencrypted(dev))
-		return 0;
 	ret = set_memory_encrypted((unsigned long)vaddr, PFN_UP(size));
 	if (ret)
 		pr_warn_ratelimited("leaking DMA memory that can't be re-encrypted\n");
@@ -169,7 +172,8 @@ static void *dma_direct_alloc_from_pool(struct device *dev, size_t size,
 				   dma_coherent_ok);
 	if (!page)
 		return NULL;
-	*dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
+	*dma_handle = phys_to_dma_direct(dev, page_to_phys(page),
+					 !!(attrs & DMA_ATTR_CC_SHARED));
 	return ret;
 }
 
@@ -185,9 +189,11 @@ static void *dma_direct_alloc_no_mapping(struct device *dev, size_t size,
 	/* remove any dirty cache lines on the kernel alias */
 	if (!PageHighMem(page))
 		arch_dma_prep_coherent(page, size);
-
-	/* return the page pointer as the opaque cookie */
-	*dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
+	/*
+	 * return the page pointer as the opaque cookie.
+	 * Never used for unencrypted allocation
+	 */
+	*dma_handle = phys_to_dma_encrypted(dev, page_to_phys(page));
 	return page;
 }
 
@@ -332,7 +338,8 @@ void *dma_direct_alloc(struct device *dev, size_t size,
 		ret = uncached_cpu_addr;
 	}
 
-	*dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
+	*dma_handle = phys_to_dma_direct(dev, page_to_phys(page),
+					 !!(attrs & DMA_ATTR_CC_SHARED));
 	return ret;

@@ -455,11 +462,12 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size,
 		return NULL;
 
 	ret = page_address(page);
-	if (dma_set_decrypted(dev, ret, size))
+	if ((attrs & DMA_ATTR_CC_SHARED) && dma_set_decrypted(dev, ret, size))
 		goto out_leak_pages;
 setup_page:
 	memset(ret, 0, size);
-	*dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
+	*dma_handle = phys_to_dma_direct(dev, page_to_phys(page),
+					 !!(attrs & DMA_ATTR_CC_SHARED));
 	return page;
 out_leak_pages:
 	return NULL;
-- 
2.43.0