On Tue, Feb 27, 2018 at 01:07:06PM +0100, Christian König wrote:
> Hi guys,
>
> at least on amdgpu and radeon the page array allocated by ttm_dma_tt_init is
> completely unused in the case of DMA-buf sharing. So I'm trying to get rid
> of that by only allocating the DMA address array.
>
> Now the only other user of DMA-buf together with ttm_dma_tt_init is Nouveau.
> So my question is are you guys using the page array anywhere in your kernel
> driver in case of a DMA-buf sharing?
>
> If no then I could just make this the default behavior for all drivers and
> save quite a bit of memory for everybody.
+1 on teaching ttm to no longer look at the struct page * in the dma-buf
sgt, but only the dma_buf address.
If there's still some need for in-kernel cpu or userspace mmap access then
imo ttm needs to be fixed to delegate all that to the right dma-buf
interfaces. The ttm abstraction is already there, it's just not passed
through.
I don't pretend to now enough of the details to review this stuff :-)
-Daniel
>
> Thanks,
> Christian.
>
> Am 27.02.2018 um 12:49 schrieb Christian König:
> > This allows drivers to only allocate dma addresses, but not a page
> > array.
> >
> > Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> > ---
> > drivers/gpu/drm/ttm/ttm_tt.c | 54 ++++++++++++++++++++++++++++++++++++--------
> > include/drm/ttm/ttm_tt.h | 2 ++
> > 2 files changed, 47 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
> > index 8e0b525cda00..971133106ec2 100644
> > --- a/drivers/gpu/drm/ttm/ttm_tt.c
> > +++ b/drivers/gpu/drm/ttm/ttm_tt.c
> > @@ -108,6 +108,16 @@ static int ttm_dma_tt_alloc_page_directory(struct ttm_dma_tt *ttm)
> > return 0;
> > }
> > +static int ttm_sg_tt_alloc_page_directory(struct ttm_dma_tt *ttm)
> > +{
> > + ttm->dma_address = kvmalloc_array(ttm->ttm.num_pages,
> > + sizeof(*ttm->dma_address),
> > + GFP_KERNEL | __GFP_ZERO);
> > + if (!ttm->dma_address)
> > + return -ENOMEM;
> > + return 0;
> > +}
> > +
> > #ifdef CONFIG_X86
> > static inline int ttm_tt_set_page_caching(struct page *p,
> > enum ttm_caching_state c_old,
> > @@ -227,8 +237,8 @@ void ttm_tt_destroy(struct ttm_tt *ttm)
> > ttm->func->destroy(ttm);
> > }
> > -int ttm_tt_init(struct ttm_tt *ttm, struct ttm_bo_device *bdev,
> > - unsigned long size, uint32_t page_flags)
> > +void ttm_tt_init_fields(struct ttm_tt *ttm, struct ttm_bo_device *bdev,
> > + unsigned long size, uint32_t page_flags)
> > {
> > ttm->bdev = bdev;
> > ttm->num_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
> > @@ -236,6 +246,12 @@ int ttm_tt_init(struct ttm_tt *ttm, struct ttm_bo_device *bdev,
> > ttm->page_flags = page_flags;
> > ttm->state = tt_unpopulated;
> > ttm->swap_storage = NULL;
> > +}
> > +
> > +int ttm_tt_init(struct ttm_tt *ttm, struct ttm_bo_device *bdev,
> > + unsigned long size, uint32_t page_flags)
> > +{
> > + ttm_tt_init_fields(ttm, bdev, size, page_flags);
> > if (ttm_tt_alloc_page_directory(ttm)) {
> > ttm_tt_destroy(ttm);
> > @@ -258,12 +274,7 @@ int ttm_dma_tt_init(struct ttm_dma_tt *ttm_dma, struct ttm_bo_device *bdev,
> > {
> > struct ttm_tt *ttm = &ttm_dma->ttm;
> > - ttm->bdev = bdev;
> > - ttm->num_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
> > - ttm->caching_state = tt_cached;
> > - ttm->page_flags = page_flags;
> > - ttm->state = tt_unpopulated;
> > - ttm->swap_storage = NULL;
> > + ttm_tt_init_fields(ttm, bdev, size, page_flags);
> > INIT_LIST_HEAD(&ttm_dma->pages_list);
> > if (ttm_dma_tt_alloc_page_directory(ttm_dma)) {
> > @@ -275,11 +286,36 @@ int ttm_dma_tt_init(struct ttm_dma_tt *ttm_dma, struct ttm_bo_device *bdev,
> > }
> > EXPORT_SYMBOL(ttm_dma_tt_init);
> > +int ttm_sg_tt_init(struct ttm_dma_tt *ttm_dma, struct ttm_bo_device *bdev,
> > + unsigned long size, uint32_t page_flags)
> > +{
> > + struct ttm_tt *ttm = &ttm_dma->ttm;
> > + int ret;
> > +
> > + ttm_tt_init_fields(ttm, bdev, size, page_flags);
> > +
> > + INIT_LIST_HEAD(&ttm_dma->pages_list);
> > + if (page_flags & TTM_PAGE_FLAG_SG)
> > + ret = ttm_sg_tt_alloc_page_directory(ttm_dma);
> > + else
> > + ret = ttm_dma_tt_alloc_page_directory(ttm_dma);
> > + if (ret) {
> > + ttm_tt_destroy(ttm);
> > + pr_err("Failed allocating page table\n");
> > + return -ENOMEM;
> > + }
> > + return 0;
> > +}
> > +EXPORT_SYMBOL(ttm_sg_tt_init);
> > +
> > void ttm_dma_tt_fini(struct ttm_dma_tt *ttm_dma)
> > {
> > struct ttm_tt *ttm = &ttm_dma->ttm;
> > - kvfree(ttm->pages);
> > + if (ttm->pages)
> > + kvfree(ttm->pages);
> > + else
> > + kvfree(ttm_dma->dma_address);
> > ttm->pages = NULL;
> > ttm_dma->dma_address = NULL;
> > }
> > diff --git a/include/drm/ttm/ttm_tt.h b/include/drm/ttm/ttm_tt.h
> > index 9c78556b488e..1cf316a4257c 100644
> > --- a/include/drm/ttm/ttm_tt.h
> > +++ b/include/drm/ttm/ttm_tt.h
> > @@ -163,6 +163,8 @@ int ttm_tt_init(struct ttm_tt *ttm, struct ttm_bo_device *bdev,
> > unsigned long size, uint32_t page_flags);
> > int ttm_dma_tt_init(struct ttm_dma_tt *ttm_dma, struct ttm_bo_device *bdev,
> > unsigned long size, uint32_t page_flags);
> > +int ttm_sg_tt_init(struct ttm_dma_tt *ttm_dma, struct ttm_bo_device *bdev,
> > + unsigned long size, uint32_t page_flags);
> > /**
> > * ttm_tt_fini
>
> _______________________________________________
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> Nouveau@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/nouveau
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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