Re: [RFC][PATCH 4/6 v3] dma-buf: heaps: Add CMA heap to dmabuf heapss

[Andrew F. Davis]

On 3/29/19 9:44 AM, Benjamin Gaignard wrote:
> Le ven. 29 mars 2019 Ã 01:16, John Stultz <john.stultz@xxxxxxxxxx> a Ãcrit :
>>
>> This adds a CMA heap, which allows userspace to allocate
>> a dma-buf of contiguous memory out of a CMA region.
>>
>> This code is an evolution of the Android ION implementation, so
>> thanks to its original author and maintainters:
>>   Benjamin Gaignard, Laura Abbott, and others!
>>
>> Cc: Laura Abbott <labbott@xxxxxxxxxx>
>> Cc: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
>> Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
>> Cc: Liam Mark <lmark@xxxxxxxxxxxxxx>
>> Cc: Pratik Patel <pratikp@xxxxxxxxxxxxxx>
>> Cc: Brian Starkey <Brian.Starkey@xxxxxxx>
>> Cc: Vincent Donnefort <Vincent.Donnefort@xxxxxxx>
>> Cc: Sudipto Paul <Sudipto.Paul@xxxxxxx>
>> Cc: Andrew F. Davis <afd@xxxxxx>
>> Cc: Xu YiPing <xuyiping@xxxxxxxxxxxxx>
>> Cc: "Chenfeng (puck)" <puck.chen@xxxxxxxxxxxxx>
>> Cc: butao <butao@xxxxxxxxxxxxx>
>> Cc: "Xiaqing (A)" <saberlily.xia@xxxxxxxxxxxxx>
>> Cc: Yudongbin <yudongbin@xxxxxxxxxxxxx>
>> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
>> Cc: Chenbo Feng <fengc@xxxxxxxxxx>
>> Cc: Alistair Strachan <astrachan@xxxxxxxxxx>
>> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
>> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
>> ---
>> v2:
>> * Switch allocate to return dmabuf fd
>> * Simplify init code
>> * Checkpatch fixups
>> v3:
>> * Switch to inline function for to_cma_heap()
>> * Minor cleanups suggested by Brian
>> * Fold in new registration style from Andrew
>> * Folded in changes from Andrew to use simplified page list
>>   from the heap helpers
>> ---
>>  drivers/dma-buf/heaps/Kconfig    |   8 ++
>>  drivers/dma-buf/heaps/Makefile   |   1 +
>>  drivers/dma-buf/heaps/cma_heap.c | 170 +++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 179 insertions(+)
>>  create mode 100644 drivers/dma-buf/heaps/cma_heap.c
>>
>> diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
>> index 2050527..a5eef06 100644
>> --- a/drivers/dma-buf/heaps/Kconfig
>> +++ b/drivers/dma-buf/heaps/Kconfig
>> @@ -4,3 +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"
>> +       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/Makefile b/drivers/dma-buf/heaps/Makefile
>> index d1808ec..6e54cde 100644
>> --- a/drivers/dma-buf/heaps/Makefile
>> +++ b/drivers/dma-buf/heaps/Makefile
>> @@ -1,3 +1,4 @@
>>  # SPDX-License-Identifier: GPL-2.0
>>  obj-y                                  += heap-helpers.o
>>  obj-$(CONFIG_DMABUF_HEAPS_SYSTEM)      += system_heap.o
>> +obj-$(CONFIG_DMABUF_HEAPS_CMA)         += cma_heap.o
>> diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
>> new file mode 100644
>> index 0000000..f4485c60
>> --- /dev/null
>> +++ b/drivers/dma-buf/heaps/cma_heap.c
>> @@ -0,0 +1,170 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * DMABUF CMA heap exporter
>> + *
>> + * Copyright (C) 2012, 2019 Linaro Ltd.
>> + * Author: <benjamin.gaignard@xxxxxxxxxx> for ST-Ericsson.
>> + */
>> +
>> +#include <linux/device.h>
>> +#include <linux/dma-buf.h>
>> +#include <linux/dma-heap.h>
>> +#include <linux/slab.h>
>> +#include <linux/errno.h>
>> +#include <linux/err.h>
>> +#include <linux/cma.h>
>> +#include <linux/scatterlist.h>
>> +#include <linux/highmem.h>
>> +
>> +#include "heap-helpers.h"
>> +
>> +struct cma_heap {
>> +       struct dma_heap *heap;
>> +       struct cma *cma;
>> +};
>> +
>> +static void cma_heap_free(struct heap_helper_buffer *buffer)
>> +{
>> +       struct cma_heap *cma_heap = dma_heap_get_data(buffer->heap_buffer.heap);
>> +       struct page *pages = buffer->priv_virt;
>> +       unsigned long nr_pages;
>> +
>> +       nr_pages = buffer->heap_buffer.size >> PAGE_SHIFT;
>> +
>> +       /* free page list */
>> +       kfree(buffer->pages);
>> +       /* release memory */
>> +       cma_release(cma_heap->cma, pages, nr_pages);
>> +       kfree(buffer);
>> +}
>> +
>> +/* dmabuf heap CMA operations functions */
>> +static int cma_heap_allocate(struct dma_heap *heap,
>> +                               unsigned long len,
>> +                               unsigned long flags)
>> +{
>> +       struct cma_heap *cma_heap = dma_heap_get_data(heap);
>> +       struct heap_helper_buffer *helper_buffer;
>> +       struct page *pages;
>> +       size_t size = PAGE_ALIGN(len);
>> +       unsigned long nr_pages = size >> PAGE_SHIFT;
>> +       unsigned long align = get_order(size);
>> +       DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
>> +       struct dma_buf *dmabuf;
>> +       int ret = -ENOMEM;
>> +       pgoff_t pg;
>> +
>> +       if (align > CONFIG_CMA_ALIGNMENT)
>> +               align = CONFIG_CMA_ALIGNMENT;
>> +
>> +       helper_buffer = kzalloc(sizeof(*helper_buffer), GFP_KERNEL);
>> +       if (!helper_buffer)
>> +               return -ENOMEM;
>> +
>> +       INIT_HEAP_HELPER_BUFFER(helper_buffer, cma_heap_free);
>> +       helper_buffer->heap_buffer.flags = flags;
>> +       helper_buffer->heap_buffer.heap = heap;
>> +       helper_buffer->heap_buffer.size = len;
>> +
>> +       pages = cma_alloc(cma_heap->cma, nr_pages, align, false);
>> +       if (!pages)
>> +               goto free_buf;
>> +
>> +       if (PageHighMem(pages)) {
>> +               unsigned long nr_clear_pages = nr_pages;
>> +               struct page *page = pages;
>> +
>> +               while (nr_clear_pages > 0) {
>> +                       void *vaddr = kmap_atomic(page);
>> +
>> +                       memset(vaddr, 0, PAGE_SIZE);
>> +                       kunmap_atomic(vaddr);
>> +                       page++;
>> +                       nr_clear_pages--;
>> +               }
>> +       } else {
>> +               memset(page_address(pages), 0, size);
>> +       }
>> +
>> +       helper_buffer->pagecount = nr_pages;
>> +       helper_buffer->pages = kmalloc_array(helper_buffer->pagecount,
>> +                                            sizeof(*helper_buffer->pages),
>> +                                            GFP_KERNEL);
>> +       if (!helper_buffer->pages) {
>> +               ret = -ENOMEM;
>> +               goto free_cma;
>> +       }
>> +
>> +       for (pg = 0; pg < helper_buffer->pagecount; pg++) {
>> +               helper_buffer->pages[pg] = &pages[pg];
>> +               if (!helper_buffer->pages[pg])
>> +                       goto free_pages;
>> +       }
>> +
>> +       /* create the dmabuf */
>> +       exp_info.ops = &heap_helper_ops;
>> +       exp_info.size = len;
>> +       exp_info.flags = O_RDWR;
> 
> I think that the flags should be provided when requesting the allocation
> like it is done in DRM or V4L2.
> For me DMA_HEAP_VALID_FLAGS = (O_CLOEXEC | O_ACCMODE).
> 


So something like done in udmabuf?

https://elixir.bootlin.com/linux/v5.1-rc1/source/include/uapi/linux/udmabuf.h#L8

I think that can be arranged.

John,

This might be a good reason to move the dma_buf_fd() call below out of
the heap and back into the core. That way the file exporting flags can
be common and core handled. I don't think it would complicate the error
handling any as we only need to dma_buf_put(dmabuf) in the core on
failure and the heap specific cleanup will happen for us.

Andrew


> Benjamin
> 
> Benjamin
> 
>> +       exp_info.priv = &helper_buffer->heap_buffer;
>> +       dmabuf = dma_buf_export(&exp_info);
>> +       if (IS_ERR(dmabuf)) {
>> +               ret = PTR_ERR(dmabuf);
>> +               goto free_pages;
>> +       }
>> +
>> +       helper_buffer->heap_buffer.dmabuf = dmabuf;
>> +       helper_buffer->priv_virt = pages;
>> +
>> +       ret = dma_buf_fd(dmabuf, O_CLOEXEC);
>> +       if (ret < 0) {
>> +               dma_buf_put(dmabuf);
>> +               /* just return, as put will call release and that will free */
>> +               return ret;
>> +       }
>> +
>> +       return ret;
>> +
>> +free_pages:
>> +       kfree(helper_buffer->pages);
>> +free_cma:
>> +       cma_release(cma_heap->cma, pages, nr_pages);
>> +free_buf:
>> +       kfree(helper_buffer);
>> +       return ret;
>> +}
>> +
>> +static struct dma_heap_ops cma_heap_ops = {
>> +       .allocate = cma_heap_allocate,
>> +};
>> +
>> +static int __add_cma_heap(struct cma *cma, void *data)
>> +{
>> +       struct cma_heap *cma_heap;
>> +       struct dma_heap_export_info exp_info;
>> +
>> +       cma_heap = kzalloc(sizeof(*cma_heap), GFP_KERNEL);
>> +       if (!cma_heap)
>> +               return -ENOMEM;
>> +       cma_heap->cma = cma;
>> +
>> +       exp_info.name = cma_get_name(cma);
>> +       exp_info.ops = &cma_heap_ops;
>> +       exp_info.priv = cma_heap;
>> +
>> +       cma_heap->heap = dma_heap_add(&exp_info);
>> +       if (IS_ERR(cma_heap->heap)) {
>> +               int ret = PTR_ERR(cma_heap->heap);
>> +
>> +               kfree(cma_heap);
>> +               return ret;
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +static int add_cma_heaps(void)
>> +{
>> +       cma_for_each_area(__add_cma_heap, NULL);
>> +       return 0;
>> +}
>> +device_initcall(add_cma_heaps);
>> --
>> 2.7.4
>>