[PATCH v5 0/4] dma-buf: heaps: Turn heaps into modules

[PATCH v5 0/4] dma-buf: heaps: Turn heaps into modules

[Maxime Ripard]

Hi,

The recent introduction of heaps in the optee driver [1] made possible
the creation of heaps as modules.

It's generally a good idea if possible, including for the already
existing system and CMA heaps.

The system one is pretty trivial, the CMA is now easy too with the
reworks we got in 7.1-r1.

Let me know what you think,
Maxime

1: https://lore.kernel.org/dri-devel/20250911135007.1275833-4-jens.wiklander@linaro.org/

Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
Changes in v5:
- Rebase on 7.1-rc1
- Add a patch to enable the heaps in arm64 defconfig
- Link to v4: https://lore.kernel.org/r/20260331-dma-buf-heaps-as-modules-v4-0-e18fda504419@kernel.org

Changes in v4:
- Fix compilation failure
- Rework to take into account OF_RESERVED_MEM
- Fix regression making the default CMA area disappear if not created
  through the DT
- Added some documentation and comments
- Link to v3: https://lore.kernel.org/r/20260303-dma-buf-heaps-as-modules-v3-0-24344812c707@kernel.org

Changes in v3:
- Squashed cma_get_name and cma_alloc/release patches
- Fixed typo in Export dev_get_cma_area commit title
- Fixed compilation failure with DMA_CMA but not OF_RESERVED_MEM
- Link to v2: https://lore.kernel.org/r/20260227-dma-buf-heaps-as-modules-v2-0-454aee7e06cc@kernel.org

Changes in v2:
- Collect tags
- Don't export dma_contiguous_default_area anymore, but export
  dev_get_cma_area instead
- Mentioned that heap modules can't be removed
- Link to v1: https://lore.kernel.org/r/20260225-dma-buf-heaps-as-modules-v1-0-2109225a090d@kernel.org

---
Maxime Ripard (4):
      dma-buf: heaps: Export mem_accounting parameter
      dma-buf: heaps: cma: Turn the heap into a module
      dma-buf: heaps: system: Turn the heap into a module
      arm64: defconfig: Enable dma-buf heaps

 arch/arm64/configs/defconfig        | 3 +++
 drivers/dma-buf/dma-heap.c          | 1 +
 drivers/dma-buf/heaps/Kconfig       | 4 ++--
 drivers/dma-buf/heaps/cma_heap.c    | 3 +++
 drivers/dma-buf/heaps/system_heap.c | 5 +++++
 5 files changed, 14 insertions(+), 2 deletions(-)
---
base-commit: 5e9b7d093f3f77cb0af4409559e3d139babfb443
change-id: 20260225-dma-buf-heaps-as-modules-1034b3ec9f2a

Best regards,
-- 
Maxime Ripard <mripard@kernel.org>

[PATCH v5 1/4] dma-buf: heaps: Export mem_accounting parameter

[Maxime Ripard]

The mem_accounting kernel parameter is used by heaps to know if they
should account allocations in their respective cgroup controllers.

Since we're going to allow heaps to compile as modules, we need to
export that variable.

Reviewed-by: T.J. Mercier <tjmercier@google.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
 drivers/dma-buf/dma-heap.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
index ac5f8685a649..a76bf3f8b071 100644
--- a/drivers/dma-buf/dma-heap.c
+++ b/drivers/dma-buf/dma-heap.c
@@ -51,10 +51,11 @@ static DEFINE_XARRAY_ALLOC(dma_heap_minors);
 
 bool __read_mostly mem_accounting;
 module_param(mem_accounting, bool, 0444);
 MODULE_PARM_DESC(mem_accounting,
 		 "Enable cgroup-based memory accounting for dma-buf heap allocations (default=false).");
+EXPORT_SYMBOL_NS_GPL(mem_accounting, "DMA_BUF_HEAP");
 
 static int dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
 				 u32 fd_flags,
 				 u64 heap_flags)
 {

-- 
2.53.0

[PATCH v5 2/4] dma-buf: heaps: cma: Turn the heap into a module

[Maxime Ripard]

All the symbols used by the CMA heap are already exported, so turning it
into a module is straightforward. We only need to add the usual MODULE_*
macros, import the proper namespaces and change the Kconfig symbol to a
tristate.

This heap won't be able to unload though, since we're missing a lot of
infrastructure to make it safe.

Reviewed-by: T.J. Mercier <tjmercier@google.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
 drivers/dma-buf/heaps/Kconfig    | 2 +-
 drivers/dma-buf/heaps/cma_heap.c | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
index a5eef06c4226..aed0b9b4febf 100644
--- a/drivers/dma-buf/heaps/Kconfig
+++ b/drivers/dma-buf/heaps/Kconfig
@@ -4,11 +4,11 @@ config DMABUF_HEAPS_SYSTEM
 	help
 	  Choose this option to enable the system dmabuf heap. The system heap
 	  is backed by pages from the buddy allocator. If in doubt, say Y.
 
 config DMABUF_HEAPS_CMA
-	bool "DMA-BUF CMA Heap"
+	tristate "DMA-BUF CMA Heap"
 	depends on DMABUF_HEAPS && DMA_CMA
 	help
 	  Choose this option to enable dma-buf CMA heap. This heap is backed
 	  by the Contiguous Memory Allocator (CMA). If your system has these
 	  regions, you should say Y here.
diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
index a359aac45579..3fb4b946c91a 100644
--- a/drivers/dma-buf/heaps/cma_heap.c
+++ b/drivers/dma-buf/heaps/cma_heap.c
@@ -418,5 +418,8 @@ static int __init add_cma_heaps(void)
 
 	return 0;
 }
 module_init(add_cma_heaps);
 MODULE_DESCRIPTION("DMA-BUF CMA Heap");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("DMA_BUF");
+MODULE_IMPORT_NS("DMA_BUF_HEAP");

-- 
2.53.0

[PATCH v5 3/4] dma-buf: heaps: system: Turn the heap into a module

[Maxime Ripard]

The system heap can be easily turned into a module by adding the usual
MODULE_* macros, importing the proper namespaces and changing the
Kconfig symbol to a tristate.

This heap won't be able to unload though, since we're missing a lot of
infrastructure to make it safe.

Reviewed-by: T.J. Mercier <tjmercier@google.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
 drivers/dma-buf/heaps/Kconfig       | 2 +-
 drivers/dma-buf/heaps/system_heap.c | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
index aed0b9b4febf..e273fb18feca 100644
--- a/drivers/dma-buf/heaps/Kconfig
+++ b/drivers/dma-buf/heaps/Kconfig
@@ -1,7 +1,7 @@
 config DMABUF_HEAPS_SYSTEM
-	bool "DMA-BUF System Heap"
+	tristate "DMA-BUF System Heap"
 	depends on DMABUF_HEAPS
 	help
 	  Choose this option to enable the system dmabuf heap. The system heap
 	  is backed by pages from the buddy allocator. If in doubt, say Y.
 
diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index 03c2b87cb111..c92bdec356fc 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -535,5 +535,10 @@ static int __init system_heap_create(void)
 		return PTR_ERR(sys_heap);
 
 	return 0;
 }
 module_init(system_heap_create);
+
+MODULE_DESCRIPTION("DMA-BUF System Heap");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("DMA_BUF");
+MODULE_IMPORT_NS("DMA_BUF_HEAP");

-- 
2.53.0

[PATCH v5 4/4] arm64: defconfig: Enable dma-buf heaps

[Maxime Ripard]

Now that the system and CMA heaps can be built as modules, enable both
as modules in the arm64 defconfig.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
 arch/arm64/configs/defconfig | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
index d905a0777f93..f33193b50e6b 100644
--- a/arch/arm64/configs/defconfig
+++ b/arch/arm64/configs/defconfig
@@ -1409,10 +1409,13 @@ CONFIG_RCAR_DMAC=y
 CONFIG_RENESAS_USB_DMAC=m
 CONFIG_RZ_DMAC=y
 CONFIG_TI_K3_UDMA=y
 CONFIG_TI_K3_UDMA_GLUE_LAYER=y
 CONFIG_STM32_DMA3=m
+CONFIG_DMABUF_HEAPS=y
+CONFIG_DMABUF_HEAPS_SYSTEM=m
+CONFIG_DMABUF_HEAPS_CMA=m
 CONFIG_VFIO=y
 CONFIG_VFIO_PCI=y
 CONFIG_VIRTIO_PCI=y
 CONFIG_VIRTIO_BALLOON=y
 CONFIG_VIRTIO_MMIO=y

-- 
2.53.0

Re: [PATCH v5 0/4] dma-buf: heaps: Turn heaps into modules

[Andrew Davis]

On 4/27/26 5:04 AM, Maxime Ripard wrote:
> Hi,
> 
> The recent introduction of heaps in the optee driver [1] made possible
> the creation of heaps as modules.
> 
> It's generally a good idea if possible, including for the already
> existing system and CMA heaps.
> 
> The system one is pretty trivial, the CMA is now easy too with the
> reworks we got in 7.1-r1.
> 
> Let me know what you think,
> Maxime
> 
> 1: https://lore.kernel.org/dri-devel/20250911135007.1275833-4-jens.wiklander@linaro.org/
> 
> Signed-off-by: Maxime Ripard <mripard@kernel.org>
> ---
> Changes in v5:
> - Rebase on 7.1-rc1
> - Add a patch to enable the heaps in arm64 defconfig

Could you do this for ARM (multi_v7_defconfig) also? Actually seems
loongarch has Heaps enabled by default and I've seen it default enabled
on some x86 distros too. Maybe someday having the base Heaps + System Heap
set to "default y/m" as they should always exist for any arch would be an
idea. Anyway for this series all LGTM,

Acked-by: Andrew Davis <afd@ti.com>

> - Link to v4: https://lore.kernel.org/r/20260331-dma-buf-heaps-as-modules-v4-0-e18fda504419@kernel.org
> 
> Changes in v4:
> - Fix compilation failure
> - Rework to take into account OF_RESERVED_MEM
> - Fix regression making the default CMA area disappear if not created
>    through the DT
> - Added some documentation and comments
> - Link to v3: https://lore.kernel.org/r/20260303-dma-buf-heaps-as-modules-v3-0-24344812c707@kernel.org
> 
> Changes in v3:
> - Squashed cma_get_name and cma_alloc/release patches
> - Fixed typo in Export dev_get_cma_area commit title
> - Fixed compilation failure with DMA_CMA but not OF_RESERVED_MEM
> - Link to v2: https://lore.kernel.org/r/20260227-dma-buf-heaps-as-modules-v2-0-454aee7e06cc@kernel.org
> 
> Changes in v2:
> - Collect tags
> - Don't export dma_contiguous_default_area anymore, but export
>    dev_get_cma_area instead
> - Mentioned that heap modules can't be removed
> - Link to v1: https://lore.kernel.org/r/20260225-dma-buf-heaps-as-modules-v1-0-2109225a090d@kernel.org
> 
> ---
> Maxime Ripard (4):
>        dma-buf: heaps: Export mem_accounting parameter
>        dma-buf: heaps: cma: Turn the heap into a module
>        dma-buf: heaps: system: Turn the heap into a module
>        arm64: defconfig: Enable dma-buf heaps
> 
>   arch/arm64/configs/defconfig        | 3 +++
>   drivers/dma-buf/dma-heap.c          | 1 +
>   drivers/dma-buf/heaps/Kconfig       | 4 ++--
>   drivers/dma-buf/heaps/cma_heap.c    | 3 +++
>   drivers/dma-buf/heaps/system_heap.c | 5 +++++
>   5 files changed, 14 insertions(+), 2 deletions(-)
> ---
> base-commit: 5e9b7d093f3f77cb0af4409559e3d139babfb443
> change-id: 20260225-dma-buf-heaps-as-modules-1034b3ec9f2a
> 
> Best regards,