[PATCH v9 07/14] swiotlb: Bounce data from/to restricted DMA pool if available

[Claire Chang]

Regardless of swiotlb setting, the restricted DMA pool is preferred if
available.

The restricted DMA pools provide a basic level of protection against the
DMA overwriting buffer contents at unexpected times. However, to protect
against general data leakage and system memory corruption, the system
needs to provide a way to lock down the memory access, e.g., MPU.

Note that is_dev_swiotlb_force doesn't check if
swiotlb_force == SWIOTLB_FORCE. Otherwise the memory allocation behavior
with default swiotlb will be changed by the following patche
("dma-direct: Allocate memory from restricted DMA pool if available").

Signed-off-by: Claire Chang <tientzu@xxxxxxxxxxxx>
---
 include/linux/swiotlb.h | 10 +++++++++-
 kernel/dma/direct.c     |  3 ++-
 kernel/dma/direct.h     |  3 ++-
 kernel/dma/swiotlb.c    |  1 +
 4 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 06cf17a80f5c..8200c100fe10 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -85,6 +85,7 @@ extern enum swiotlb_force swiotlb_force;
  *		unmap calls.
  * @debugfs:	The dentry to debugfs.
  * @late_alloc:	%true if allocated using the page allocator
+ * @force_swiotlb: %true if swiotlb is forced
  */
 struct io_tlb_mem {
 	phys_addr_t start;
@@ -95,6 +96,7 @@ struct io_tlb_mem {
 	spinlock_t lock;
 	struct dentry *debugfs;
 	bool late_alloc;
+	bool force_swiotlb;
 	struct io_tlb_slot {
 		phys_addr_t orig_addr;
 		size_t alloc_size;
@@ -115,6 +117,11 @@ static inline void swiotlb_set_io_tlb_default_mem(struct device *dev)
 	dev->dma_io_tlb_mem = io_tlb_default_mem;
 }
 
+static inline bool is_dev_swiotlb_force(struct device *dev)
+{
+	return dev->dma_io_tlb_mem->force_swiotlb;
+}
+
 void __init swiotlb_exit(void);
 unsigned int swiotlb_max_segment(void);
 size_t swiotlb_max_mapping_size(struct device *dev);
@@ -126,8 +133,9 @@ static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr)
 {
 	return false;
 }
-static inline void swiotlb_set_io_tlb_default_mem(struct device *dev)
+static inline bool is_dev_swiotlb_force(struct device *dev)
 {
+	return false;
 }
 static inline void swiotlb_exit(void)
 {
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 7a88c34d0867..078f7087e466 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -496,7 +496,8 @@ size_t dma_direct_max_mapping_size(struct device *dev)
 {
 	/* If SWIOTLB is active, use its maximum mapping size */
 	if (is_swiotlb_active(dev) &&
-	    (dma_addressing_limited(dev) || swiotlb_force == SWIOTLB_FORCE))
+	    (dma_addressing_limited(dev) || swiotlb_force == SWIOTLB_FORCE ||
+	     is_dev_swiotlb_force(dev)))
 		return swiotlb_max_mapping_size(dev);
 	return SIZE_MAX;
 }
diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h
index 13e9e7158d94..f94813674e23 100644
--- a/kernel/dma/direct.h
+++ b/kernel/dma/direct.h
@@ -87,7 +87,8 @@ static inline dma_addr_t dma_direct_map_page(struct device *dev,
 	phys_addr_t phys = page_to_phys(page) + offset;
 	dma_addr_t dma_addr = phys_to_dma(dev, phys);
 
-	if (unlikely(swiotlb_force == SWIOTLB_FORCE))
+	if (unlikely(swiotlb_force == SWIOTLB_FORCE) ||
+	    is_dev_swiotlb_force(dev))
 		return swiotlb_map(dev, phys, size, dir, attrs);
 
 	if (unlikely(!dma_capable(dev, dma_addr, size, true))) {
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 21e99907edd6..e5ccc198d0a7 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -714,6 +714,7 @@ static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
 			return -ENOMEM;
 
 		swiotlb_init_io_tlb_mem(mem, rmem->base, nslabs, false, true);
+		mem->force_swiotlb = true;
 
 		rmem->priv = mem;
 
-- 
2.32.0.272.g935e593368-goog