On 2025-03-10 12:06 pm, Maxime Ripard wrote:
Consumers of the direct DMA API will have to know which region their
device allocate from in order for them to charge the memory allocation
in the right one.
This doesn't seem to make much sense - dma-direct is not an allocator
itself, it just provides the high-level
dma_alloc_attrs/dma_alloc_pages/etc. interfaces wherein the underlying
allocations _could_ come from CMA, but also a per-device
coherent/restricted pool, or a global coherent/atomic pool, or the
regular page allocator, or in one weird corner case the SWIOTLB buffer,
or...
Thanks,
Robin.
Let's provide an accessor for that region.
Signed-off-by: Maxime Ripard <mripard@xxxxxxxxxx>
---
include/linux/dma-direct.h | 2 ++
kernel/dma/direct.c | 8 ++++++++
2 files changed, 10 insertions(+)
diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index d7e30d4f7503a898a456df8eedf6a2cd284c35ff..2dd7cbccfaeed81c18c67aae877417fe89f2f2f5 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -145,6 +145,8 @@ void dma_direct_free_pages(struct device *dev, size_t size,
enum dma_data_direction dir);
int dma_direct_supported(struct device *dev, u64 mask);
dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
size_t size, enum dma_data_direction dir, unsigned long attrs);
+struct dmem_cgroup_region *dma_direct_get_dmem_cgroup_region(struct device *dev);
+
#endif /* _LINUX_DMA_DIRECT_H */
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 5b4e6d3bf7bcca8930877ba078aed4ce26828f06..ece1361077b6efeec5b202d838750afd967d473f 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -42,10 +42,18 @@ u64 dma_direct_get_required_mask(struct device *dev)
u64 max_dma = phys_to_dma_direct(dev, phys);
return (1ULL << (fls64(max_dma) - 1)) * 2 - 1;
}
+#if IS_ENABLED(CONFIG_CGROUP_DMEM)
+struct dmem_cgroup_region *
+dma_direct_get_dmem_cgroup_region(struct device *dev)
+{
+ return dma_contiguous_get_dmem_cgroup_region(dev);
+}
+#endif
+
static gfp_t dma_direct_optimal_gfp_mask(struct device *dev, u64 *phys_limit)
{
u64 dma_limit = min_not_zero(
dev->coherent_dma_mask,
dev->bus_dma_limit);
