Expose DT coherent reserved-memory pools ("shared-dma-pool" without "reusable") as dma-buf heaps, creating one heap per region so userspace can allocate from the exact device-local pool intended for coherent DMA.
This is a missing backend in the long-term effort to steer userspace buffer allocations (DRM, v4l2, dma-buf heaps) through heaps for clearer cgroup accounting. CMA and system heaps already exist; non-reusable coherent reserved memory did not.
The heap binds the heap device to each memory region so coherent allocations use the correct dev->dma_mem, and it defers registration until module_init when normal allocators are available.
Signed-off-by: Albert Esteve aesteve@redhat.com --- drivers/dma-buf/heaps/Kconfig | 9 + drivers/dma-buf/heaps/Makefile | 1 + drivers/dma-buf/heaps/coherent_heap.c | 414 ++++++++++++++++++++++++++++++++++ 3 files changed, 424 insertions(+)
diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig index a5eef06c42264..aeb475e585048 100644 --- a/drivers/dma-buf/heaps/Kconfig +++ b/drivers/dma-buf/heaps/Kconfig @@ -12,3 +12,12 @@ config DMABUF_HEAPS_CMA 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. + +config DMABUF_HEAPS_COHERENT + bool "DMA-BUF Coherent Reserved-Memory Heap" + depends on DMABUF_HEAPS && OF_RESERVED_MEM && DMA_DECLARE_COHERENT + help + Choose this option to enable coherent reserved-memory dma-buf heaps. + This heap is backed by non-reusable DT "shared-dma-pool" regions. + If your system defines coherent reserved-memory regions, you should + say Y here. diff --git a/drivers/dma-buf/heaps/Makefile b/drivers/dma-buf/heaps/Makefile index 974467791032f..96bda7a65f041 100644 --- a/drivers/dma-buf/heaps/Makefile +++ b/drivers/dma-buf/heaps/Makefile @@ -1,3 +1,4 @@ # SPDX-License-Identifier: GPL-2.0 obj-$(CONFIG_DMABUF_HEAPS_SYSTEM) += system_heap.o obj-$(CONFIG_DMABUF_HEAPS_CMA) += cma_heap.o +obj-$(CONFIG_DMABUF_HEAPS_COHERENT) += coherent_heap.o diff --git a/drivers/dma-buf/heaps/coherent_heap.c b/drivers/dma-buf/heaps/coherent_heap.c new file mode 100644 index 0000000000000..55f53f87c4c15 --- /dev/null +++ b/drivers/dma-buf/heaps/coherent_heap.c @@ -0,0 +1,414 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * DMABUF heap for coherent reserved-memory regions + * + * Copyright (C) 2026 Red Hat, Inc. + * Author: Albert Esteve aesteve@redhat.com + * + */ + +#include <linux/dma-buf.h> +#include <linux/dma-heap.h> +#include <linux/dma-map-ops.h> +#include <linux/dma-mapping.h> +#include <linux/err.h> +#include <linux/highmem.h> +#include <linux/iosys-map.h> +#include <linux/of_reserved_mem.h> +#include <linux/scatterlist.h> +#include <linux/slab.h> +#include <linux/vmalloc.h> + +struct coherent_heap { + struct dma_heap *heap; + struct reserved_mem *rmem; + char *name; +}; + +struct coherent_heap_buffer { + struct coherent_heap *heap; + struct list_head attachments; + struct mutex lock; + unsigned long len; + dma_addr_t dma_addr; + void *alloc_vaddr; + struct page **pages; + pgoff_t pagecount; + int vmap_cnt; + void *vaddr; +}; + +struct dma_heap_attachment { + struct device *dev; + struct sg_table table; + struct list_head list; + bool mapped; +}; + +static int coherent_heap_attach(struct dma_buf *dmabuf, + struct dma_buf_attachment *attachment) +{ + struct coherent_heap_buffer *buffer = dmabuf->priv; + struct dma_heap_attachment *a; + int ret; + + a = kzalloc_obj(*a); + if (!a) + return -ENOMEM; + + ret = sg_alloc_table_from_pages(&a->table, buffer->pages, + buffer->pagecount, 0, + buffer->pagecount << PAGE_SHIFT, + GFP_KERNEL); + if (ret) { + kfree(a); + return ret; + } + + a->dev = attachment->dev; + INIT_LIST_HEAD(&a->list); + a->mapped = false; + + attachment->priv = a; + + mutex_lock(&buffer->lock); + list_add(&a->list, &buffer->attachments); + mutex_unlock(&buffer->lock); + + return 0; +} + +static void coherent_heap_detach(struct dma_buf *dmabuf, + struct dma_buf_attachment *attachment) +{ + struct coherent_heap_buffer *buffer = dmabuf->priv; + struct dma_heap_attachment *a = attachment->priv; + + mutex_lock(&buffer->lock); + list_del(&a->list); + mutex_unlock(&buffer->lock); + + sg_free_table(&a->table); + kfree(a); +} + +static struct sg_table *coherent_heap_map_dma_buf(struct dma_buf_attachment *attachment, + enum dma_data_direction direction) +{ + struct dma_heap_attachment *a = attachment->priv; + struct sg_table *table = &a->table; + int ret; + + ret = dma_map_sgtable(attachment->dev, table, direction, 0); + if (ret) + return ERR_PTR(-ENOMEM); + a->mapped = true; + + return table; +} + +static void coherent_heap_unmap_dma_buf(struct dma_buf_attachment *attachment, + struct sg_table *table, + enum dma_data_direction direction) +{ + struct dma_heap_attachment *a = attachment->priv; + + a->mapped = false; + dma_unmap_sgtable(attachment->dev, table, direction, 0); +} + +static int coherent_heap_dma_buf_begin_cpu_access(struct dma_buf *dmabuf, + enum dma_data_direction direction) +{ + struct coherent_heap_buffer *buffer = dmabuf->priv; + struct dma_heap_attachment *a; + + mutex_lock(&buffer->lock); + if (buffer->vmap_cnt) + invalidate_kernel_vmap_range(buffer->vaddr, buffer->len); + + list_for_each_entry(a, &buffer->attachments, list) { + if (!a->mapped) + continue; + dma_sync_sgtable_for_cpu(a->dev, &a->table, direction); + } + mutex_unlock(&buffer->lock); + + return 0; +} + +static int coherent_heap_dma_buf_end_cpu_access(struct dma_buf *dmabuf, + enum dma_data_direction direction) +{ + struct coherent_heap_buffer *buffer = dmabuf->priv; + struct dma_heap_attachment *a; + + mutex_lock(&buffer->lock); + if (buffer->vmap_cnt) + flush_kernel_vmap_range(buffer->vaddr, buffer->len); + + list_for_each_entry(a, &buffer->attachments, list) { + if (!a->mapped) + continue; + dma_sync_sgtable_for_device(a->dev, &a->table, direction); + } + mutex_unlock(&buffer->lock); + + return 0; +} + +static int coherent_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) +{ + struct coherent_heap_buffer *buffer = dmabuf->priv; + struct coherent_heap *coh_heap = buffer->heap; + struct device *heap_dev = dma_heap_get_dev(coh_heap->heap); + + return dma_mmap_coherent(heap_dev, vma, buffer->alloc_vaddr, + buffer->dma_addr, buffer->len); +} + +static void *coherent_heap_do_vmap(struct coherent_heap_buffer *buffer) +{ + void *vaddr; + + vaddr = vmap(buffer->pages, buffer->pagecount, VM_MAP, PAGE_KERNEL); + if (!vaddr) + return ERR_PTR(-ENOMEM); + + return vaddr; +} + +static int coherent_heap_vmap(struct dma_buf *dmabuf, struct iosys_map *map) +{ + struct coherent_heap_buffer *buffer = dmabuf->priv; + void *vaddr; + int ret = 0; + + mutex_lock(&buffer->lock); + if (buffer->vmap_cnt) { + buffer->vmap_cnt++; + iosys_map_set_vaddr(map, buffer->vaddr); + goto out; + } + + vaddr = coherent_heap_do_vmap(buffer); + if (IS_ERR(vaddr)) { + ret = PTR_ERR(vaddr); + goto out; + } + + buffer->vaddr = vaddr; + buffer->vmap_cnt++; + iosys_map_set_vaddr(map, buffer->vaddr); +out: + mutex_unlock(&buffer->lock); + + return ret; +} + +static void coherent_heap_vunmap(struct dma_buf *dmabuf, struct iosys_map *map) +{ + struct coherent_heap_buffer *buffer = dmabuf->priv; + + mutex_lock(&buffer->lock); + if (!--buffer->vmap_cnt) { + vunmap(buffer->vaddr); + buffer->vaddr = NULL; + } + mutex_unlock(&buffer->lock); + iosys_map_clear(map); +} + +static void coherent_heap_dma_buf_release(struct dma_buf *dmabuf) +{ + struct coherent_heap_buffer *buffer = dmabuf->priv; + struct coherent_heap *coh_heap = buffer->heap; + struct device *heap_dev = dma_heap_get_dev(coh_heap->heap); + + if (buffer->vmap_cnt > 0) { + WARN(1, "%s: buffer still mapped in the kernel\n", __func__); + vunmap(buffer->vaddr); + buffer->vaddr = NULL; + buffer->vmap_cnt = 0; + } + + if (buffer->alloc_vaddr) + dma_free_coherent(heap_dev, buffer->len, buffer->alloc_vaddr, + buffer->dma_addr); + kfree(buffer->pages); + kfree(buffer); +} + +static const struct dma_buf_ops coherent_heap_buf_ops = { + .attach = coherent_heap_attach, + .detach = coherent_heap_detach, + .map_dma_buf = coherent_heap_map_dma_buf, + .unmap_dma_buf = coherent_heap_unmap_dma_buf, + .begin_cpu_access = coherent_heap_dma_buf_begin_cpu_access, + .end_cpu_access = coherent_heap_dma_buf_end_cpu_access, + .mmap = coherent_heap_mmap, + .vmap = coherent_heap_vmap, + .vunmap = coherent_heap_vunmap, + .release = coherent_heap_dma_buf_release, +}; + +static struct dma_buf *coherent_heap_allocate(struct dma_heap *heap, + unsigned long len, + u32 fd_flags, + u64 heap_flags) +{ + struct coherent_heap *coh_heap; + struct coherent_heap_buffer *buffer; + struct device *heap_dev; + DEFINE_DMA_BUF_EXPORT_INFO(exp_info); + size_t size = PAGE_ALIGN(len); + pgoff_t pagecount = size >> PAGE_SHIFT; + struct dma_buf *dmabuf; + int ret = -ENOMEM; + pgoff_t pg; + + coh_heap = dma_heap_get_drvdata(heap); + if (!coh_heap) + return ERR_PTR(-EINVAL); + + heap_dev = dma_heap_get_dev(coh_heap->heap); + if (!heap_dev) + return ERR_PTR(-ENODEV); + + buffer = kzalloc_obj(*buffer); + if (!buffer) + return ERR_PTR(-ENOMEM); + + INIT_LIST_HEAD(&buffer->attachments); + mutex_init(&buffer->lock); + buffer->len = size; + buffer->heap = coh_heap; + buffer->pagecount = pagecount; + + buffer->alloc_vaddr = dma_alloc_coherent(heap_dev, buffer->len, + &buffer->dma_addr, GFP_KERNEL); + if (!buffer->alloc_vaddr) { + ret = -ENOMEM; + goto free_buffer; + } + + buffer->pages = kmalloc_array(pagecount, sizeof(*buffer->pages), + GFP_KERNEL); + if (!buffer->pages) { + ret = -ENOMEM; + goto free_dma; + } + + for (pg = 0; pg < pagecount; pg++) + buffer->pages[pg] = virt_to_page((char *)buffer->alloc_vaddr + + (pg * PAGE_SIZE)); + + /* create the dmabuf */ + exp_info.exp_name = dma_heap_get_name(heap); + exp_info.ops = &coherent_heap_buf_ops; + exp_info.size = buffer->len; + exp_info.flags = fd_flags; + exp_info.priv = buffer; + dmabuf = dma_buf_export(&exp_info); + if (IS_ERR(dmabuf)) { + ret = PTR_ERR(dmabuf); + goto free_pages; + } + return dmabuf; + +free_pages: + kfree(buffer->pages); +free_dma: + dma_free_coherent(heap_dev, buffer->len, buffer->alloc_vaddr, + buffer->dma_addr); +free_buffer: + kfree(buffer); + return ERR_PTR(ret); +} + +static const struct dma_heap_ops coherent_heap_ops = { + .allocate = coherent_heap_allocate, +}; + +static int __coherent_heap_register(struct reserved_mem *rmem) +{ + struct dma_heap_export_info exp_info; + struct coherent_heap *coh_heap; + struct device *heap_dev; + int ret; + + if (!rmem || !rmem->name) + return -EINVAL; + + coh_heap = kzalloc_obj(*coh_heap); + if (!coh_heap) + return -ENOMEM; + + coh_heap->rmem = rmem; + coh_heap->name = kstrdup(rmem->name, GFP_KERNEL); + if (!coh_heap->name) { + ret = -ENOMEM; + goto free_coherent_heap; + } + + exp_info.name = coh_heap->name; + exp_info.ops = &coherent_heap_ops; + exp_info.priv = coh_heap; + + coh_heap->heap = dma_heap_create(&exp_info); + if (IS_ERR(coh_heap->heap)) { + ret = PTR_ERR(coh_heap->heap); + goto free_name; + } + + heap_dev = dma_heap_get_dev(coh_heap->heap); + ret = dma_coerce_mask_and_coherent(heap_dev, DMA_BIT_MASK(64)); + if (ret) { + pr_err("coherent_heap: failed to set DMA mask (%d)\n", ret); + goto destroy_heap; + } + + ret = of_reserved_mem_device_init_with_mem(heap_dev, rmem); + if (ret) { + pr_err("coherent_heap: failed to initialize memory (%d)\n", ret); + goto destroy_heap; + } + + ret = dma_heap_register(coh_heap->heap); + if (ret) { + pr_err("coherent_heap: failed to register heap (%d)\n", ret); + goto destroy_heap; + } + + return 0; + +destroy_heap: + dma_heap_destroy(coh_heap->heap); + coh_heap->heap = NULL; +free_name: + kfree(coh_heap->name); +free_coherent_heap: + kfree(coh_heap); + + return ret; +} + +static int __init coherent_heap_register(void) +{ + struct reserved_mem *rmem; + unsigned int i; + int ret; + + for (i = 0; (rmem = dma_coherent_get_reserved_region(i)) != NULL; i++) { + ret = __coherent_heap_register(rmem); + if (ret) { + pr_warn("Failed to add coherent heap %s", + rmem->name ? rmem->name : "unknown"); + continue; + } + } + + return 0; +} +module_init(coherent_heap_register); +MODULE_DESCRIPTION("DMA-BUF heap for coherent reserved-memory regions");