On Mon, Jun 14, 2021 at 07:45:36PM +0200, Christian König wrote:
> Drop the workaround and instead implement a better solution.
>
> Basically we are now chaining all submissions using a dma_fence_chain
> container and adding them as exclusive fence to the dma_resv object.
>
> This way other drivers can still sync to the single exclusive fence
> while amdgpu only sync to fences from different processes.
>
> v3: add the shared fence first before the exclusive one
>
> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h | 1 +
> drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 62 ++++++++++++++++----
> drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 65 ---------------------
> drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 3 +-
> drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 2 +-
> drivers/gpu/drm/amd/amdgpu/amdgpu_object.h | 1 -
> 6 files changed, 55 insertions(+), 79 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h
> index a130e766cbdb..c905a4cfc173 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h
> @@ -34,6 +34,7 @@ struct amdgpu_fpriv;
> struct amdgpu_bo_list_entry {
> struct ttm_validate_buffer tv;
> struct amdgpu_bo_va *bo_va;
> + struct dma_fence_chain *chain;
> uint32_t priority;
> struct page **user_pages;
> bool user_invalidated;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> index 9ce649a1a8d3..25655414e9c0 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> @@ -572,6 +572,20 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
> goto out;
> }
>
> + amdgpu_bo_list_for_each_entry(e, p->bo_list) {
> + struct amdgpu_bo *bo = ttm_to_amdgpu_bo(e->tv.bo);
> +
> + e->bo_va = amdgpu_vm_bo_find(vm, bo);
> +
> + if (bo->tbo.base.dma_buf && !amdgpu_bo_explicit_sync(bo)) {
> + e->chain = dma_fence_chain_alloc();
> + if (!e->chain) {
> + r = -ENOMEM;
> + goto error_validate;
> + }
> + }
> + }
> +
> amdgpu_cs_get_threshold_for_moves(p->adev, &p->bytes_moved_threshold,
> &p->bytes_moved_vis_threshold);
> p->bytes_moved = 0;
> @@ -599,15 +613,6 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
> gws = p->bo_list->gws_obj;
> oa = p->bo_list->oa_obj;
>
> - amdgpu_bo_list_for_each_entry(e, p->bo_list) {
> - struct amdgpu_bo *bo = ttm_to_amdgpu_bo(e->tv.bo);
> -
> - /* Make sure we use the exclusive slot for shared BOs */
> - if (bo->prime_shared_count)
> - e->tv.num_shared = 0;
> - e->bo_va = amdgpu_vm_bo_find(vm, bo);
> - }
> -
> if (gds) {
> p->job->gds_base = amdgpu_bo_gpu_offset(gds) >> PAGE_SHIFT;
> p->job->gds_size = amdgpu_bo_size(gds) >> PAGE_SHIFT;
> @@ -629,8 +634,13 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
> }
>
> error_validate:
> - if (r)
> + if (r) {
> + amdgpu_bo_list_for_each_entry(e, p->bo_list) {
> + dma_fence_chain_free(e->chain);
> + e->chain = NULL;
> + }
> ttm_eu_backoff_reservation(&p->ticket, &p->validated);
> + }
> out:
> return r;
> }
> @@ -670,9 +680,17 @@ static void amdgpu_cs_parser_fini(struct amdgpu_cs_parser *parser, int error,
> {
> unsigned i;
>
> - if (error && backoff)
> + if (error && backoff) {
> + struct amdgpu_bo_list_entry *e;
> +
> + amdgpu_bo_list_for_each_entry(e, parser->bo_list) {
> + dma_fence_chain_free(e->chain);
> + e->chain = NULL;
> + }
> +
> ttm_eu_backoff_reservation(&parser->ticket,
> &parser->validated);
> + }
>
> for (i = 0; i < parser->num_post_deps; i++) {
> drm_syncobj_put(parser->post_deps[i].syncobj);
> @@ -1245,6 +1263,28 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
>
> amdgpu_vm_move_to_lru_tail(p->adev, &fpriv->vm);
>
> + amdgpu_bo_list_for_each_entry(e, p->bo_list) {
> + struct dma_resv *resv = e->tv.bo->base.resv;
> + struct dma_fence_chain *chain = e->chain;
> +
> + if (!chain)
> + continue;
> +
> + /*
> + * Work around dma_resv shortcommings by wrapping up the
> + * submission in a dma_fence_chain and add it as exclusive
> + * fence, but first add the submission as shared fence to make
> + * sure that shared fences never signal before the exclusive
> + * one.
> + */
> + dma_fence_chain_init(chain, dma_resv_excl_fence(resv),
> + dma_fence_get(p->fence), 1);
> +
> + dma_resv_add_shared_fence(resv, p->fence);
> + rcu_assign_pointer(resv->fence_excl, &chain->base);
Ok I should have looked more carefully, +/- memory barriers this looks
correct.
So my idea behind the dma_resv_add_shared_exclusive_fence helper was that
it would give us more flexibility for changing the internals. Since I do
like your idea from a few weeks back of just storing exclusive fences as
shared ones, but with a marker, and then the interface functions picking
the right set of fences depending what the caller wants. But for that we'd
need to drop a lot more abstraction of the internals into dma_resv and
make sure everyone is using it.
Because looking at drivers there's indeed both the concept of a truly
exclusive fence, and the "it's actually a shared fence but stuff it into
the exclusive fence slot for implicit sync" variety. And from what I can
see, everyone gets it wrong, but in lots of different ways.
Hence the wrapper for this concept, and then making sure we roll it out to
all the drivers. I think all the ones with a NO_IMPLICIT flag (or
equivalent, i915 and msm have it the other way round iirc) would need this
to not break the dma_resv contract too badly.
But also I guess we can bikeshed this later on even more.
On this: Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> + e->chain = NULL;
> + }
> +
> ttm_eu_fence_buffer_objects(&p->ticket, &p->validated, p->fence);
> mutex_unlock(&p->adev->notifier_lock);
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> index c3053b83b80c..23219fc3b28c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> @@ -42,48 +42,6 @@
> #include <linux/pci-p2pdma.h>
> #include <linux/pm_runtime.h>
>
> -static int
> -__dma_resv_make_exclusive(struct dma_resv *obj)
> -{
> - struct dma_fence **fences;
> - unsigned int count;
> - int r;
> -
> - if (!dma_resv_shared_list(obj)) /* no shared fences to convert */
> - return 0;
> -
> - r = dma_resv_get_fences(obj, NULL, &count, &fences);
> - if (r)
> - return r;
> -
> - if (count == 0) {
> - /* Now that was unexpected. */
> - } else if (count == 1) {
> - dma_resv_add_excl_fence(obj, fences[0]);
> - dma_fence_put(fences[0]);
> - kfree(fences);
> - } else {
> - struct dma_fence_array *array;
> -
> - array = dma_fence_array_create(count, fences,
> - dma_fence_context_alloc(1), 0,
> - false);
> - if (!array)
> - goto err_fences_put;
> -
> - dma_resv_add_excl_fence(obj, &array->base);
> - dma_fence_put(&array->base);
> - }
> -
> - return 0;
> -
> -err_fences_put:
> - while (count--)
> - dma_fence_put(fences[count]);
> - kfree(fences);
> - return -ENOMEM;
> -}
> -
> /**
> * amdgpu_dma_buf_attach - &dma_buf_ops.attach implementation
> *
> @@ -110,24 +68,6 @@ static int amdgpu_dma_buf_attach(struct dma_buf *dmabuf,
> if (r < 0)
> goto out;
>
> - r = amdgpu_bo_reserve(bo, false);
> - if (unlikely(r != 0))
> - goto out;
> -
> - /*
> - * We only create shared fences for internal use, but importers
> - * of the dmabuf rely on exclusive fences for implicitly
> - * tracking write hazards. As any of the current fences may
> - * correspond to a write, we need to convert all existing
> - * fences on the reservation object into a single exclusive
> - * fence.
> - */
> - r = __dma_resv_make_exclusive(bo->tbo.base.resv);
> - if (r)
> - goto out;
> -
> - bo->prime_shared_count++;
> - amdgpu_bo_unreserve(bo);
> return 0;
>
> out:
> @@ -150,9 +90,6 @@ static void amdgpu_dma_buf_detach(struct dma_buf *dmabuf,
> struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
> struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
>
> - if (attach->dev->driver != adev->dev->driver && bo->prime_shared_count)
> - bo->prime_shared_count--;
> -
> pm_runtime_mark_last_busy(adev_to_drm(adev)->dev);
> pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
> }
> @@ -406,8 +343,6 @@ amdgpu_dma_buf_create_obj(struct drm_device *dev, struct dma_buf *dma_buf)
> bo = gem_to_amdgpu_bo(gobj);
> bo->allowed_domains = AMDGPU_GEM_DOMAIN_GTT;
> bo->preferred_domains = AMDGPU_GEM_DOMAIN_GTT;
> - if (dma_buf->ops != &amdgpu_dmabuf_ops)
> - bo->prime_shared_count = 1;
>
> dma_resv_unlock(resv);
> return gobj;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> index 9cf4beaf646c..0780e8d18992 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> @@ -829,7 +829,8 @@ int amdgpu_gem_op_ioctl(struct drm_device *dev, void *data,
> break;
> }
> case AMDGPU_GEM_OP_SET_PLACEMENT:
> - if (robj->prime_shared_count && (args->value & AMDGPU_GEM_DOMAIN_VRAM)) {
> + if (robj->tbo.base.import_attach &&
> + args->value & AMDGPU_GEM_DOMAIN_VRAM) {
> r = -EINVAL;
> amdgpu_bo_unreserve(robj);
> break;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> index b7a2070d90af..d13490975ac3 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> @@ -892,7 +892,7 @@ int amdgpu_bo_pin_restricted(struct amdgpu_bo *bo, u32 domain,
> return -EINVAL;
>
> /* A shared bo cannot be migrated to VRAM */
> - if (bo->prime_shared_count || bo->tbo.base.import_attach) {
> + if (bo->tbo.base.import_attach) {
> if (domain & AMDGPU_GEM_DOMAIN_GTT)
> domain = AMDGPU_GEM_DOMAIN_GTT;
> else
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
> index 126df03a7066..c03dfd298f45 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
> @@ -99,7 +99,6 @@ struct amdgpu_bo {
> struct ttm_buffer_object tbo;
> struct ttm_bo_kmap_obj kmap;
> u64 flags;
> - unsigned prime_shared_count;
> /* per VM structure for page tables and with virtual addresses */
> struct amdgpu_vm_bo_base *vm_bo;
> /* Constant after initialization */
> --
> 2.25.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
