diff mbox series

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

Message ID 20210611152659.2142983-8-tientzu@chromium.org (mailing list archive)
State Superseded
Delegated to: Bjorn Helgaas
Headers show
Series Restricted DMA | expand

Commit Message

Claire Chang June 11, 2021, 3:26 p.m. UTC
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 | 10 +++++++++-
 kernel/dma/direct.c     |  3 ++-
 kernel/dma/direct.h     |  3 ++-
 kernel/dma/swiotlb.c    |  1 +
 4 files changed, 14 insertions(+), 3 deletions(-)

Comments

Christoph Hellwig June 14, 2021, 6:25 a.m. UTC | #1
On Fri, Jun 11, 2021 at 11:26:52PM +0800, Claire Chang wrote:
> 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 | 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)))

I think we can remove the extra swiotlb_force check here if the
swiotlb_force setting is propagated into io_tlb_default_mem->force
when that is initialized. This avoids an extra check in the fast path.

> -	if (unlikely(swiotlb_force == SWIOTLB_FORCE))
> +	if (unlikely(swiotlb_force == SWIOTLB_FORCE) ||
> +	    is_dev_swiotlb_force(dev))

Same here.
diff mbox series

Patch

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;