[PATCH v4 08/14] swiotlb: Use restricted DMA pool if available

Claire Chang
2021-02-09T06:29:24Z

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.

Signed-off-by: Claire Chang <tientzu@chromium.org>
---
include/linux/swiotlb.h | 13 +++++++++++++
kernel/dma/direct.h | 2 +-
kernel/dma/swiotlb.c | 20 +++++++++++++++++---
3 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index f13a52a97382..76f86c684524 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -71,6 +71,15 @@ dma_addr_t swiotlb_map(struct device *dev, phys_addr_t phys,
#ifdef CONFIG_SWIOTLB
extern enum swiotlb_force swiotlb_force;

+#ifdef CONFIG_DMA_RESTRICTED_POOL
+bool is_swiotlb_force(struct device *dev);
+#else
+static inline bool is_swiotlb_force(struct device *dev)
+{
+ return unlikely(swiotlb_force == SWIOTLB_FORCE);
+}
+#endif /* CONFIG_DMA_RESTRICTED_POOL */
+
bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr);
void __init swiotlb_exit(void);
unsigned int swiotlb_max_segment(void);
@@ -80,6 +89,10 @@ phys_addr_t get_swiotlb_start(struct device *dev);
void __init swiotlb_adjust_size(unsigned long new_size);
#else
#define swiotlb_force SWIOTLB_NO_FORCE
+static inline bool is_swiotlb_force(struct device *dev)
+{
+ return false;
+}
static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr)
{
return false;
diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h
index 7b83b1595989..b011db1b625d 100644
--- a/kernel/dma/direct.h
+++ b/kernel/dma/direct.h
@@ -87,7 +87,7 @@ 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 (is_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 e22e7ae75f1c..6fdebde8fb1f 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -40,6 +40,7 @@
#include <linux/debugfs.h>
#endif
#ifdef CONFIG_DMA_RESTRICTED_POOL
+#include <linux/device.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_fdt.h>
@@ -109,6 +110,10 @@ static struct swiotlb default_swiotlb;

static inline struct swiotlb *get_swiotlb(struct device *dev)
{
+#ifdef CONFIG_DMA_RESTRICTED_POOL
+ if (dev && dev->dev_swiotlb)
+ return dev->dev_swiotlb;
+#endif
return &default_swiotlb;
}

@@ -508,7 +513,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, phys_addr_t orig_addr,
size_t mapping_size, size_t alloc_size,
enum dma_data_direction dir, unsigned long attrs)
{
- struct swiotlb *swiotlb = &default_swiotlb;
+ struct swiotlb *swiotlb = get_swiotlb(hwdev);
dma_addr_t tbl_dma_addr = phys_to_dma_unencrypted(hwdev, swiotlb->start);
unsigned long flags;
phys_addr_t tlb_addr;
@@ -519,7 +524,11 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, phys_addr_t orig_addr,
unsigned long max_slots;
unsigned long tmp_io_tlb_used;

+#ifdef CONFIG_DMA_RESTRICTED_POOL
+ if (no_iotlb_memory && !hwdev->dev_swiotlb)
+#else
if (no_iotlb_memory)
+#endif
panic("Can not allocate SWIOTLB buffer earlier and can't now provide you with the DMA bounce buffer");

if (mem_encrypt_active())
@@ -641,7 +650,7 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
size_t mapping_size, size_t alloc_size,
enum dma_data_direction dir, unsigned long attrs)
{
- struct swiotlb *swiotlb = &default_swiotlb;
+ struct swiotlb *swiotlb = get_swiotlb(hwdev);
unsigned long flags;
int i, count, nslots = ALIGN(alloc_size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
int index = (tlb_addr - swiotlb->start) >> IO_TLB_SHIFT;
@@ -689,7 +698,7 @@ void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr,
size_t size, enum dma_data_direction dir,
enum dma_sync_target target)
{
- struct swiotlb *swiotlb = &default_swiotlb;
+ struct swiotlb *swiotlb = get_swiotlb(hwdev);
int index = (tlb_addr - swiotlb->start) >> IO_TLB_SHIFT;
phys_addr_t orig_addr = swiotlb->orig_addr[index];

@@ -801,6 +810,11 @@ late_initcall(swiotlb_create_default_debugfs);
#endif

#ifdef CONFIG_DMA_RESTRICTED_POOL
+bool is_swiotlb_force(struct device *dev)
+{
+ return unlikely(swiotlb_force == SWIOTLB_FORCE) || dev->dev_swiotlb;
+}
+
static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
struct device *dev)
{
--
2.30.0.478.g8a0d178c01-goog