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@li...
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-e18fda50441...
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-v3-0-24344812c70...
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-v2-0-454aee7e06c...
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-v1-0-2109225a090...
--- 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,
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) {
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");
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");
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
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-
Maxime Ripard