[RFC PATCH 4/7] dma: swiotlb: track pool encryption state and honor DMA_ATTR_CC_DECRYPTED

["Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>]

Teach swiotlb to distinguish between encrypted and decrypted bounce
buffer pools, and make allocation and mapping paths select a pool whose
state matches the requested DMA attributes.

Add a decrypted flag to io_tlb_mem, initialize it for the default and
restricted pools, and propagate DMA_ATTR_CC_DECRYPTED into swiotlb pool
allocation. Reject swiotlb alloc/map requests when the selected pool does
not match the required encrypted/decrypted state.

Also return DMA addresses with the matching phys_to_dma_{encrypted,
unencrypted} helper so the DMA address encoding stays consistent with the
chosen pool.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 include/linux/dma-direct.h | 10 +++++
 include/linux/swiotlb.h    |  7 ++-
 kernel/dma/direct.c        | 14 ++++--
 kernel/dma/swiotlb.c       | 89 ++++++++++++++++++++++++++++++--------
 4 files changed, 95 insertions(+), 25 deletions(-)

diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index c249912456f9..94fad4e7c11e 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -77,6 +77,10 @@ static inline dma_addr_t dma_range_map_max(const struct bus_dma_region *map)
 #ifndef phys_to_dma_unencrypted
 #define phys_to_dma_unencrypted		phys_to_dma
 #endif
+
+#ifndef phys_to_dma_encrypted
+#define phys_to_dma_encrypted		phys_to_dma
+#endif
 #else
 static inline dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr)
 {
@@ -90,6 +94,12 @@ static inline dma_addr_t phys_to_dma_unencrypted(struct device *dev,
 {
 	return dma_addr_unencrypted(__phys_to_dma(dev, paddr));
 }
+
+static inline dma_addr_t phys_to_dma_encrypted(struct device *dev,
+		phys_addr_t paddr)
+{
+	return dma_addr_encrypted(__phys_to_dma(dev, paddr));
+}
 /*
  * If memory encryption is supported, phys_to_dma will set the memory encryption
  * bit in the DMA address, and dma_to_phys will clear it.
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 3dae0f592063..382753ba3f06 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -111,6 +111,7 @@ struct io_tlb_mem {
 	struct dentry *debugfs;
 	bool force_bounce;
 	bool for_alloc;
+	bool decrypted;
 #ifdef CONFIG_SWIOTLB_DYNAMIC
 	bool can_grow;
 	u64 phys_limit;
@@ -282,7 +283,8 @@ static inline void swiotlb_sync_single_for_cpu(struct device *dev,
 extern void swiotlb_print_info(void);
 
 #ifdef CONFIG_DMA_RESTRICTED_POOL
-struct page *swiotlb_alloc(struct device *dev, size_t size);
+struct page *swiotlb_alloc(struct device *dev, size_t size,
+		unsigned long attrs);
 bool swiotlb_free(struct device *dev, struct page *page, size_t size);
 
 static inline bool is_swiotlb_for_alloc(struct device *dev)
@@ -290,7 +292,8 @@ static inline bool is_swiotlb_for_alloc(struct device *dev)
 	return dev->dma_io_tlb_mem->for_alloc;
 }
 #else
-static inline struct page *swiotlb_alloc(struct device *dev, size_t size)
+static inline struct page *swiotlb_alloc(struct device *dev, size_t size,
+		unsigned long attrs)
 {
 	return NULL;
 }
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index ba1c731e001d..4a4147fffc5e 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -104,9 +104,10 @@ static void __dma_direct_free_pages(struct device *dev, struct page *page,
 	dma_free_contiguous(dev, page, size);
 }
 
-static struct page *dma_direct_alloc_swiotlb(struct device *dev, size_t size)
+static struct page *dma_direct_alloc_swiotlb(struct device *dev, size_t size,
+		unsigned long attrs)
 {
-	struct page *page = swiotlb_alloc(dev, size);
+	struct page *page = swiotlb_alloc(dev, size, attrs);
 
 	if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
 		swiotlb_free(dev, page, size);
@@ -256,8 +257,12 @@ void *dma_direct_alloc(struct device *dev, size_t size,
 					  gfp, attrs);
 
 	if (is_swiotlb_for_alloc(dev)) {
-		page = dma_direct_alloc_swiotlb(dev, size);
+		page = dma_direct_alloc_swiotlb(dev, size, attrs);
 		if (page) {
+			/*
+			 * swiotlb allocations comes from pool already marked
+			 * decrypted
+			 */
 			mark_mem_decrypt = false;
 			goto setup_page;
 		}
@@ -364,6 +369,7 @@ void dma_direct_free(struct device *dev, size_t size,
 		return;
 
 	if (swiotlb_find_pool(dev, dma_to_phys(dev, dma_addr)))
+		/* Swiotlb doesn't need a page attribute update on free */
 		mark_mem_encrypted = false;
 
 	if (is_vmalloc_addr(cpu_addr)) {
@@ -393,7 +399,7 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size,
 					  gfp, attrs);
 
 	if (is_swiotlb_for_alloc(dev)) {
-		page = dma_direct_alloc_swiotlb(dev, size);
+		page = dma_direct_alloc_swiotlb(dev, size, attrs);
 		if (!page)
 			return NULL;
 
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 2373a9f7e21a..1b845596b68f 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -262,7 +262,18 @@ void __init swiotlb_update_mem_attributes(void)
 	if (!mem->nslabs || mem->late_alloc)
 		return;
 	bytes = PAGE_ALIGN(mem->nslabs << IO_TLB_SHIFT);
-	set_memory_decrypted((unsigned long)mem->vaddr, bytes >> PAGE_SHIFT);
+	/*
+	 * if platform support memory encryption, swiotlb buffers are
+	 * decrypted by default.
+	 */
+	if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
+		io_tlb_default_mem.decrypted = true;
+		set_memory_decrypted((unsigned long)mem->vaddr, bytes >> PAGE_SHIFT);
+	} else {
+		io_tlb_default_mem.decrypted = false;
+	}
+
+
 }
 
 static void swiotlb_init_io_tlb_pool(struct io_tlb_pool *mem, phys_addr_t start,
@@ -505,8 +516,10 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask,
 	if (!mem->slots)
 		goto error_slots;
 
-	set_memory_decrypted((unsigned long)vstart,
-			     (nslabs << IO_TLB_SHIFT) >> PAGE_SHIFT);
+	if (io_tlb_default_mem.decrypted)
+		set_memory_decrypted((unsigned long)vstart,
+				     (nslabs << IO_TLB_SHIFT) >> PAGE_SHIFT);
+
 	swiotlb_init_io_tlb_pool(mem, virt_to_phys(vstart), nslabs, true,
 				 nareas);
 	add_mem_pool(&io_tlb_default_mem, mem);
@@ -570,7 +583,8 @@ void __init swiotlb_exit(void)
  * Return: Decrypted pages, %NULL on allocation failure, or ERR_PTR(-EAGAIN)
  * if the allocated physical address was above @phys_limit.
  */
-static struct page *alloc_dma_pages(gfp_t gfp, size_t bytes, u64 phys_limit)
+static struct page *alloc_dma_pages(gfp_t gfp, size_t bytes,
+		u64 phys_limit, bool unencrypted)
 {
 	unsigned int order = get_order(bytes);
 	struct page *page;
@@ -588,13 +602,13 @@ static struct page *alloc_dma_pages(gfp_t gfp, size_t bytes, u64 phys_limit)
 	}
 
 	vaddr = phys_to_virt(paddr);
-	if (set_memory_decrypted((unsigned long)vaddr, PFN_UP(bytes)))
+	if (unencrypted && set_memory_decrypted((unsigned long)vaddr, PFN_UP(bytes)))
 		goto error;
 	return page;
 
 error:
 	/* Intentional leak if pages cannot be encrypted again. */
-	if (!set_memory_encrypted((unsigned long)vaddr, PFN_UP(bytes)))
+	if (unencrypted && !set_memory_encrypted((unsigned long)vaddr, PFN_UP(bytes)))
 		__free_pages(page, order);
 	return NULL;
 }
@@ -604,12 +618,13 @@ static struct page *alloc_dma_pages(gfp_t gfp, size_t bytes, u64 phys_limit)
  * @dev:	Device for which a memory pool is allocated.
  * @bytes:	Size of the buffer.
  * @phys_limit:	Maximum allowed physical address of the buffer.
+ * @attrs:	DMA attributes for the allocation.
  * @gfp:	GFP flags for the allocation.
  *
  * Return: Allocated pages, or %NULL on allocation failure.
  */
 static struct page *swiotlb_alloc_tlb(struct device *dev, size_t bytes,
-		u64 phys_limit, gfp_t gfp)
+		u64 phys_limit, unsigned long attrs, gfp_t gfp)
 {
 	struct page *page;
 
@@ -617,7 +632,7 @@ static struct page *swiotlb_alloc_tlb(struct device *dev, size_t bytes,
 	 * Allocate from the atomic pools if memory is encrypted and
 	 * the allocation is atomic, because decrypting may block.
 	 */
-	if (!gfpflags_allow_blocking(gfp) && dev && force_dma_unencrypted(dev)) {
+	if (!gfpflags_allow_blocking(gfp) && (attrs & DMA_ATTR_CC_DECRYPTED)) {
 		void *vaddr;
 
 		if (!IS_ENABLED(CONFIG_DMA_COHERENT_POOL))
@@ -625,8 +640,7 @@ static struct page *swiotlb_alloc_tlb(struct device *dev, size_t bytes,
 
 		/* considered decrypted by default */
 		return dma_alloc_from_pool(dev, bytes, &vaddr, gfp,
-					   DMA_ATTR_CC_DECRYPTED,
-					   dma_coherent_ok);
+					   attrs, dma_coherent_ok);
 	}
 
 	gfp &= ~GFP_ZONEMASK;
@@ -635,7 +649,8 @@ static struct page *swiotlb_alloc_tlb(struct device *dev, size_t bytes,
 	else if (phys_limit <= DMA_BIT_MASK(32))
 		gfp |= __GFP_DMA32;
 
-	while (IS_ERR(page = alloc_dma_pages(gfp, bytes, phys_limit))) {
+	while (IS_ERR(page = alloc_dma_pages(gfp, bytes, phys_limit,
+					     !!(attrs & DMA_ATTR_CC_DECRYPTED)))) {
 		if (IS_ENABLED(CONFIG_ZONE_DMA32) &&
 		    phys_limit < DMA_BIT_MASK(64) &&
 		    !(gfp & (__GFP_DMA32 | __GFP_DMA)))
@@ -673,6 +688,7 @@ static void swiotlb_free_tlb(void *vaddr, size_t bytes)
  * @nslabs:	Desired (maximum) number of slabs.
  * @nareas:	Number of areas.
  * @phys_limit:	Maximum DMA buffer physical address.
+ * @attrs:	DMA attributes for the allocation.
  * @gfp:	GFP flags for the allocations.
  *
  * Allocate and initialize a new IO TLB memory pool. The actual number of
@@ -683,7 +699,8 @@ static void swiotlb_free_tlb(void *vaddr, size_t bytes)
  */
 static struct io_tlb_pool *swiotlb_alloc_pool(struct device *dev,
 		unsigned long minslabs, unsigned long nslabs,
-		unsigned int nareas, u64 phys_limit, gfp_t gfp)
+		unsigned int nareas, u64 phys_limit, unsigned long attrs,
+		gfp_t gfp)
 {
 	struct io_tlb_pool *pool;
 	unsigned int slot_order;
@@ -703,7 +720,7 @@ static struct io_tlb_pool *swiotlb_alloc_pool(struct device *dev,
 	pool->areas = (void *)pool + sizeof(*pool);
 
 	tlb_size = nslabs << IO_TLB_SHIFT;
-	while (!(tlb = swiotlb_alloc_tlb(dev, tlb_size, phys_limit, gfp))) {
+	while (!(tlb = swiotlb_alloc_tlb(dev, tlb_size, phys_limit, attrs, gfp))) {
 		if (nslabs <= minslabs)
 			goto error_tlb;
 		nslabs = ALIGN(nslabs >> 1, IO_TLB_SEGSIZE);
@@ -739,7 +756,9 @@ static void swiotlb_dyn_alloc(struct work_struct *work)
 	struct io_tlb_pool *pool;
 
 	pool = swiotlb_alloc_pool(NULL, IO_TLB_MIN_SLABS, default_nslabs,
-				  default_nareas, mem->phys_limit, GFP_KERNEL);
+				  default_nareas, mem->phys_limit,
+				  mem->decrypted ? DMA_ATTR_CC_DECRYPTED : 0,
+				  GFP_KERNEL);
 	if (!pool) {
 		pr_warn_ratelimited("Failed to allocate new pool");
 		return;
@@ -1226,6 +1245,7 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
 	nslabs = nr_slots(alloc_size);
 	phys_limit = min_not_zero(*dev->dma_mask, dev->bus_dma_limit);
 	pool = swiotlb_alloc_pool(dev, nslabs, nslabs, 1, phys_limit,
+				  mem->decrypted ? DMA_ATTR_CC_DECRYPTED : 0,
 				  GFP_NOWAIT);
 	if (!pool)
 		return -1;
@@ -1388,6 +1408,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
 		enum dma_data_direction dir, unsigned long attrs)
 {
 	struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
+	bool require_decrypted = false;
 	unsigned int offset;
 	struct io_tlb_pool *pool;
 	unsigned int i;
@@ -1405,6 +1426,17 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
 	if (cc_platform_has(CC_ATTR_MEM_ENCRYPT))
 		pr_warn_once("Memory encryption is active and system is using DMA bounce buffers\n");
 
+	/*
+	 * if we are trying to swiotlb map a decrypted paddr or the paddr is encrypted
+	 * but the device is forcing decryption, use decrypted io_tlb_mem
+	 */
+	if ((attrs & DMA_ATTR_CC_DECRYPTED) ||
+	    (!(attrs & DMA_ATTR_CC_DECRYPTED) && force_dma_unencrypted(dev)))
+		require_decrypted = true;
+
+	if (require_decrypted != mem->decrypted)
+		return (phys_addr_t)DMA_MAPPING_ERROR;
+
 	/*
 	 * The default swiotlb memory pool is allocated with PAGE_SIZE
 	 * alignment. If a mapping is requested with larger alignment,
@@ -1602,8 +1634,14 @@ dma_addr_t swiotlb_map(struct device *dev, phys_addr_t paddr, size_t size,
 	if (swiotlb_addr == (phys_addr_t)DMA_MAPPING_ERROR)
 		return DMA_MAPPING_ERROR;
 
-	/* Ensure that the address returned is DMA'ble */
-	dma_addr = phys_to_dma_unencrypted(dev, swiotlb_addr);
+	/*
+	 * Use the allocated io_tlb_mem encryption type to determine dma addr.
+	 */
+	if (dev->dma_io_tlb_mem->decrypted)
+		dma_addr = phys_to_dma_unencrypted(dev, swiotlb_addr);
+	else
+		dma_addr = phys_to_dma_encrypted(dev, swiotlb_addr);
+
 	if (unlikely(!dma_capable(dev, dma_addr, size, true))) {
 		__swiotlb_tbl_unmap_single(dev, swiotlb_addr, size, dir,
 			attrs | DMA_ATTR_SKIP_CPU_SYNC,
@@ -1765,7 +1803,8 @@ static inline void swiotlb_create_debugfs_files(struct io_tlb_mem *mem,
 
 #ifdef CONFIG_DMA_RESTRICTED_POOL
 
-struct page *swiotlb_alloc(struct device *dev, size_t size)
+struct page *swiotlb_alloc(struct device *dev, size_t size,
+		unsigned long attrs)
 {
 	struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
 	struct io_tlb_pool *pool;
@@ -1776,6 +1815,9 @@ struct page *swiotlb_alloc(struct device *dev, size_t size)
 	if (!mem)
 		return NULL;
 
+	if (mem->decrypted != !!(attrs & DMA_ATTR_CC_DECRYPTED))
+		return NULL;
+
 	align = (1 << (get_order(size) + PAGE_SHIFT)) - 1;
 	index = swiotlb_find_slots(dev, 0, size, align, &pool);
 	if (index == -1)
@@ -1845,9 +1887,18 @@ static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
 			kfree(mem);
 			return -ENOMEM;
 		}
+		/*
+		 * if platform supports memory encryption,
+		 * restricted mem pool is decrypted by default
+		 */
+		if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
+			mem->decrypted = true;
+			set_memory_decrypted((unsigned long)phys_to_virt(rmem->base),
+					     rmem->size >> PAGE_SHIFT);
+		} else {
+			mem->decrypted = false;
+		}
 
-		set_memory_decrypted((unsigned long)phys_to_virt(rmem->base),
-				     rmem->size >> PAGE_SHIFT);
 		swiotlb_init_io_tlb_pool(pool, rmem->base, nslabs,
 					 false, nareas);
 		mem->force_bounce = true;
-- 
2.43.0