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

[Benjamin Gaignard]

Le ven. 29 mars 2019 Ã 16:42, Andrew F. Davis <afd@xxxxxx> a Ãcrit :
>
> On 3/29/19 10:30 AM, Benjamin Gaignard wrote:
> > Le ven. 29 mars 2019 Ã 16:19, Andrew F. Davis <afd@xxxxxx> a Ãcrit :
> >>
> >> 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.
> >
> > I have in mind what is done by DRM:
> > https://elixir.bootlin.com/linux/v5.1-rc1/source/include/uapi/drm/drm.h#L707
> >
> > V4L2 does the same but without redefine the flags (which is better)
> >
>
> That would mean we would need a whole flag word passed in just for file
> flags when I only ever see one bit being useful(O_CLOEXEC or not). Do
> you see any situation where we need more than default O_RDWR and
> optional O_CLOEXEC for a dma-buf file?

Yes I really want a whole flag word because distinguish RD/WR only cases
could be useful to optimize cache maintenance (and later for secure heaps).

An other argument is that, few years ago, DRM doesn't allow at all O_RDWR
flag, but we manage to change this and make it possible.
So you believe that O_RDWR is mandatory will others O_RDWR is useless,
put it into a flag will make everybody happy :-)

Benjamin
>
> Andrew
>
> > Benjamin
> >
> >>
> >> 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
> >>>>