[PATCH V2 2/6] dma-mapping: Add vmap/vunmap_noncontiguous() callback in dma ops

Tianyu Lan
2021-11-23T14:37:07Z

Hyper-V netvsc driver needs to allocate noncontiguous DMA memory and
remap it into unencrypted address space before sharing with host. Add
vmap/vunmap_noncontiguous() callback and handle the remap in the Hyper-V
dma ops callback.

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
include/linux/dma-map-ops.h | 3 +++
kernel/dma/mapping.c | 18 ++++++++++++++----
2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 0d5b06b3a4a6..f7b9958ca20a 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -27,6 +27,9 @@ struct dma_map_ops {
unsigned long attrs);
void (*free_noncontiguous)(struct device *dev, size_t size,
struct sg_table *sgt, enum dma_data_direction dir);
+ void *(*vmap_noncontiguous)(struct device *dev, size_t size,
+ struct sg_table *sgt);
+ void (*vunmap_noncontiguous)(struct device *dev, void *addr);
int (*mmap)(struct device *, struct vm_area_struct *,
void *, dma_addr_t, size_t, unsigned long attrs);

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 9478eccd1c8e..7fd751d866cc 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -674,8 +674,14 @@ void *dma_vmap_noncontiguous(struct device *dev, size_t size,
const struct dma_map_ops *ops = get_dma_ops(dev);
unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;

- if (ops && ops->alloc_noncontiguous)
- return vmap(sgt_handle(sgt)->pages, count, VM_MAP, PAGE_KERNEL);
+ if (ops) {
+ if (ops->vmap_noncontiguous)
+ return ops->vmap_noncontiguous(dev, size, sgt);
+ else if (ops->alloc_noncontiguous)
+ return vmap(sgt_handle(sgt)->pages, count, VM_MAP,
+ PAGE_KERNEL);
+ }
+
return page_address(sg_page(sgt->sgl));
}
EXPORT_SYMBOL_GPL(dma_vmap_noncontiguous);
@@ -684,8 +690,12 @@ void dma_vunmap_noncontiguous(struct device *dev, void *vaddr)
{
const struct dma_map_ops *ops = get_dma_ops(dev);

- if (ops && ops->alloc_noncontiguous)
- vunmap(vaddr);
+ if (ops) {
+ if (ops->vunmap_noncontiguous)
+ ops->vunmap_noncontiguous(dev, vaddr);
+ else if (ops->alloc_noncontiguous)
+ vunmap(vaddr);
+ }
}
EXPORT_SYMBOL_GPL(dma_vunmap_noncontiguous);

--
2.25.1