The bounced DMA ops provide an implementation of DMA ops that bounce
streaming DMA in and out of a specially allocated region. Only the
operations relevant to streaming DMA are supported.
Signed-off-by: Claire Chang <tien...@chromium.org>
---
include/linux/device.h | 3 +
include/linux/dma-mapping.h | 1 +
kernel/dma/Kconfig | 17 +++
kernel/dma/Makefile | 1 +
kernel/dma/bounced.c | 215 ++++++++++++++++++++++++++++++++++++
5 files changed, 237 insertions(+)
create mode 100644 kernel/dma/bounced.c
diff --git a/include/linux/device.h b/include/linux/device.h
index 7322c51e9c0c..868b9a364003 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -588,6 +588,9 @@ struct device {
struct list_head dma_pools; /* dma pools (if dma'ble) */
+#ifdef CONFIG_DMA_BOUNCED
+ struct dma_bounced_mem *dma_bounced_mem;
+#endif
#ifdef CONFIG_DMA_DECLARE_COHERENT
struct dma_coherent_mem *dma_mem; /* internal for coherent mem
override */
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 2328f451a45d..86089424dafd 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -135,6 +135,7 @@ struct dma_map_ops {
extern const struct dma_map_ops dma_virt_ops;
extern const struct dma_map_ops dma_dummy_ops;
+extern const struct dma_map_ops dma_bounced_ops;
#define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index 1da3f44f2565..148734c8748b 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -88,6 +88,23 @@ config DMA_DIRECT_REMAP
select DMA_REMAP
select DMA_COHERENT_POOL
+config DMA_BOUNCED
+ bool "DMA Bounced"
+ depends on !HIGHMEM
+ select OF_RESERVED_MEM
+ help
+ This enables support for bounced DMA pools which provide a level of
+ DMA memory protection on systems with limited hardware protection
+ capabilities, such as those lacking an IOMMU. It does so by bouncing
+ the data to a specially allocated DMA-accessible protected region
+ before mapping and unmapping. One can assign the protected memory
+ region in the device tree by using reserved-memory.
+
+ For more information see
+
<Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt>
+ and <kernel/dma/bounced.c>.
+ If unsure, say "n".
+
config DMA_CMA
bool "DMA Contiguous Memory Allocator"
depends on HAVE_DMA_CONTIGUOUS && CMA
diff --git a/kernel/dma/Makefile b/kernel/dma/Makefile
index 370f63344e9c..f5fb4f42326a 100644
--- a/kernel/dma/Makefile
+++ b/kernel/dma/Makefile
@@ -1,6 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
obj-$(CONFIG_HAS_DMA) += mapping.o direct.o dummy.o
+obj-$(CONFIG_DMA_BOUNCED) += bounced.o
obj-$(CONFIG_DMA_CMA) += contiguous.o
obj-$(CONFIG_DMA_DECLARE_COHERENT) += coherent.o
obj-$(CONFIG_DMA_VIRT_OPS) += virt.o
diff --git a/kernel/dma/bounced.c b/kernel/dma/bounced.c
new file mode 100644
index 000000000000..fcaabb5eccf2
--- /dev/null
+++ b/kernel/dma/bounced.c
@@ -0,0 +1,215 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Bounced DMA support.
+ *
+ * This implements the mitigations for lack of IOMMU by bouncing the data to a
+ * specially allocated region before mapping and unmapping.
+ *
+ * Copyright 2020 Google LLC.
+ */
+#include <linux/dma-direct.h>
+#include <linux/dma-mapping.h>
+#include <linux/dma-noncoherent.h>
+#include <linux/io.h>
+#include <linux/genalloc.h>
+#include <linux/slab.h>
+
+struct dma_bounced_mem {
+ void **orig_addr;
+ void *virt_base;
+ dma_addr_t device_base;
+ dma_addr_t device_end;
+ struct gen_pool *pool;
+ size_t size;
+};
+
+static void dma_bounced_set_orig_virt(struct device *dev, dma_addr_t dma_addr,
+ void *orig_addr)
+{
+ struct dma_bounced_mem *mem = dev->dma_bounced_mem;
+ int idx = (dma_addr - mem->device_base) >> PAGE_SHIFT;
+
+ if (dma_addr < mem->device_base || dma_addr >= mem->device_end)
+ return;
+
+ mem->orig_addr[idx] = orig_addr;
+}
+
+static void *dma_bounced_get_orig_virt(struct device *dev, dma_addr_t dma_addr)
+{
+ struct dma_bounced_mem *mem = dev->dma_bounced_mem;
+ int idx = (dma_addr - mem->device_base) >> PAGE_SHIFT;
+
+ if (dma_addr < mem->device_base || dma_addr >= mem->device_end)
+ return NULL;
+
+ return mem->orig_addr[idx];
+}
+
+static void *dma_bounced_get_virt(struct device *dev, dma_addr_t dma_addr)
+{
+ struct dma_bounced_mem *mem = dev->dma_bounced_mem;
+
+ if (dma_addr < mem->device_base || dma_addr >= mem->device_end)
+ return NULL;
+
+ return (dma_addr - mem->device_base) + mem->virt_base;
+}
+
+static void dma_bounced_sync_single_for_cpu(struct device *dev,
+ dma_addr_t dma_addr, size_t size,
+ enum dma_data_direction dir)
+{
+ void *orig_virt = dma_bounced_get_orig_virt(dev, dma_addr);
+ void *bounced_virt = dma_bounced_get_virt(dev, dma_addr);
+
+ if (!orig_virt || !bounced_virt)
+ return;
+
+ dma_direct_sync_single_for_cpu(dev, dma_addr, size, dir);
+
+ if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)
+ memcpy(orig_virt, bounced_virt, size);
+}
+
+static void dma_bounced_sync_single_for_device(struct device *dev,
+ dma_addr_t dma_addr, size_t size,
+ enum dma_data_direction dir)
+{
+ void *orig_virt = dma_bounced_get_orig_virt(dev, dma_addr);
+ void *bounced_virt = dma_bounced_get_virt(dev, dma_addr);
+
+ if (!orig_virt || !bounced_virt)
+ return;
+
+ if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
+ memcpy(bounced_virt, orig_virt, size);
+
+ dma_direct_sync_single_for_device(dev, dma_addr, size, dir);
+}
+
+static void dma_bounced_sync_sg_for_cpu(struct device *dev,
+ struct scatterlist *sgl, int nents,
+ enum dma_data_direction dir)
+{
+ struct scatterlist *sg;
+ int i;
+
+ for_each_sg(sgl, sg, nents, i) {
+ dma_bounced_sync_single_for_cpu(dev, sg->dma_address,
+ sg->length, dir);
+ }
+}
+
+static void dma_bounced_sync_sg_for_device(struct device *dev,
+ struct scatterlist *sgl, int nents,
+ enum dma_data_direction dir)
+{
+ struct scatterlist *sg;
+ int i;
+
+ for_each_sg(sgl, sg, nents, i) {
+ dma_bounced_sync_single_for_device(dev, sg->dma_address,
+ sg->length, dir);
+ }
+}
+
+static void dma_bounced_unmap_page(struct device *dev, dma_addr_t dma_addr,
+ size_t size, enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ struct dma_bounced_mem *mem = dev->dma_bounced_mem;
+
+ if (dma_addr < mem->device_base || dma_addr >= mem->device_end)
+ return;
+
+ if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+ dma_bounced_sync_single_for_cpu(dev, dma_addr, size, dir);
+
+ dma_bounced_set_orig_virt(dev, dma_addr, NULL);
+ gen_pool_free(mem->pool,
+ (unsigned long)dma_bounced_get_virt(dev, dma_addr), size);
+}
+
+static dma_addr_t dma_bounced_map_page(struct device *dev, struct page *page,
+ unsigned long offset, size_t size,
+ enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ struct dma_bounced_mem *mem = dev->dma_bounced_mem;
+ dma_addr_t dma_addr;
+ void *orig_virt;
+
+ if (unlikely(!gen_pool_dma_alloc(mem->pool, size, &dma_addr)))
+ return DMA_MAPPING_ERROR;
+
+ orig_virt = page_to_virt(page) + offset;
+ dma_bounced_set_orig_virt(dev, dma_addr, orig_virt);
+
+ if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+ dma_bounced_sync_single_for_device(dev, dma_addr, size, dir);
+
+ return dma_addr;
+}
+
+static void dma_bounced_unmap_sg(struct device *dev, struct scatterlist *sgl,
+ int nents, enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ struct scatterlist *sg;
+ int i;
+
+ for_each_sg(sgl, sg, nents, i) {
+ dma_bounced_unmap_page(dev, sg->dma_address, sg_dma_len(sg),
+ dir, attrs);
+ }
+}
+
+static int dma_bounced_map_sg(struct device *dev, struct scatterlist *sgl,
+ int nents, enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ int i;
+ struct scatterlist *sg;
+
+ for_each_sg(sgl, sg, nents, i) {
+ sg->dma_address = dma_bounced_map_page(
+ dev, sg_page(sg), sg->offset, sg->length, dir, attrs);
+ if (sg->dma_address == DMA_MAPPING_ERROR)
+ goto out_unmap;
+ sg_dma_len(sg) = sg->length;
+ }
+
+ return nents;
+
+out_unmap:
+ dma_bounced_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
+ return 0;
+}
+
+static size_t dma_bounced_max_mapping_size(struct device *dev)
+{
+ return dev->dma_bounced_mem->size;
+}
+
+const struct dma_map_ops dma_bounced_ops = {
+ .alloc = NULL,
+ .free = NULL,
+ .mmap = NULL,
+ .get_sgtable = NULL,
+ .sync_single_for_cpu = dma_bounced_sync_single_for_cpu,
+ .sync_single_for_device = dma_bounced_sync_single_for_device,
+ .sync_sg_for_cpu = dma_bounced_sync_sg_for_cpu,
+ .sync_sg_for_device = dma_bounced_sync_sg_for_device,
+ .map_page = dma_bounced_map_page,
+ .unmap_page = dma_bounced_unmap_page,
+ .map_sg = dma_bounced_map_sg,
+ .unmap_sg = dma_bounced_unmap_sg,
+ .unmap_resource = NULL,
+ .map_resource = NULL,
+ .cache_sync = NULL,
+ .dma_supported = dma_direct_supported,
+ .get_required_mask = dma_direct_get_required_mask,
+ .max_mapping_size = dma_bounced_max_mapping_size,
+ .get_merge_boundary = NULL,
+};
--
2.27.0.383.g050319c2ae-goog
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