[PATCH v7 08/15] swiotlb: Bounce data from/to restricted DMA pool if available

Claire Chang
2021-05-18T06:43:45Z

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@chromium.org>
---
include/linux/swiotlb.h | 13 +++++++++++++
kernel/dma/direct.c | 3 ++-
kernel/dma/direct.h | 3 ++-
kernel/dma/swiotlb.c | 8 ++++----
4 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index c530c976d18b..0c5a18d9cf89 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -120,6 +120,15 @@ static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr)
return mem && paddr >= mem->start && paddr < mem->end;
}

+static inline bool is_dev_swiotlb_force(struct device *dev)
+{
+#ifdef CONFIG_DMA_RESTRICTED_POOL
+ if (dev->dma_io_tlb_mem)
+ return true;
+#endif /* CONFIG_DMA_RESTRICTED_POOL */
+ return false;
+}
+
void __init swiotlb_exit(void);
unsigned int swiotlb_max_segment(void);
size_t swiotlb_max_mapping_size(struct device *dev);
@@ -131,6 +140,10 @@ static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr)
{
return false;
}
+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 68e7633f11fe..95f482c4408c 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -347,7 +347,7 @@ void __init swiotlb_exit(void)
static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size,
enum dma_data_direction dir)
{
- struct io_tlb_mem *mem = io_tlb_default_mem;
+ struct io_tlb_mem *mem = get_io_tlb_mem(dev);
int index = (tlb_addr - mem->start) >> IO_TLB_SHIFT;
phys_addr_t orig_addr = mem->slots[index].orig_addr;
size_t alloc_size = mem->slots[index].alloc_size;
@@ -429,7 +429,7 @@ static unsigned int wrap_index(struct io_tlb_mem *mem, unsigned int index)
static int find_slots(struct device *dev, phys_addr_t orig_addr,
size_t alloc_size)
{
- struct io_tlb_mem *mem = io_tlb_default_mem;
+ struct io_tlb_mem *mem = get_io_tlb_mem(dev);
unsigned long boundary_mask = dma_get_seg_boundary(dev);
dma_addr_t tbl_dma_addr =
phys_to_dma_unencrypted(dev, mem->start) & boundary_mask;
@@ -506,7 +506,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
size_t mapping_size, size_t alloc_size,
enum dma_data_direction dir, unsigned long attrs)
{
- struct io_tlb_mem *mem = io_tlb_default_mem;
+ struct io_tlb_mem *mem = get_io_tlb_mem(dev);
unsigned int offset = swiotlb_align_offset(dev, orig_addr);
unsigned int i;
int index;
@@ -557,7 +557,7 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
size_t mapping_size, enum dma_data_direction dir,
unsigned long attrs)
{
- struct io_tlb_mem *mem = io_tlb_default_mem;
+ struct io_tlb_mem *mem = get_io_tlb_mem(hwdev);
unsigned long flags;
unsigned int offset = swiotlb_align_offset(hwdev, tlb_addr);
int index = (tlb_addr - offset - mem->start) >> IO_TLB_SHIFT;
--
2.31.1.751.gd2f1c929bd-goog