Re: [PATCH 2/3] drm/amdkfd: refine the gfx BO based dmabuf handling

[Lang Yu <Lang.Yu@amd.com>]

On 07/25/ , Felix Kuehling wrote:
> Am 2022-07-25 um 20:15 schrieb Lang Yu:
> > On 07/25/ , Felix Kuehling wrote:
> > > Am 2022-07-25 um 06:32 schrieb Lang Yu:
> > > > We have memory leak issue in current implenmention, i.e.,
> > > > the allocated struct kgd_mem memory is not handled properly.
> > > > 
> > > > The idea is always creating a buffer object when importing
> > > > a gfx BO based dmabuf.
> > > > 
> > > > Signed-off-by: Lang Yu <Lang.Yu@amd.com>
> > > > ---
> > > >    .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c  | 99 +++++++++++++------
> > > >    1 file changed, 70 insertions(+), 29 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> > > > index b3806ebe5ef7..c1855b72a3f0 100644
> > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> > > > @@ -225,7 +225,8 @@ void amdgpu_amdkfd_release_notify(struct amdgpu_bo *bo)
> > > >    	u32 alloc_flags = bo->kfd_bo->alloc_flags;
> > > >    	u64 size = amdgpu_bo_size(bo);
> > > > -	unreserve_mem_limit(adev, size, alloc_flags);
> > > > +	if (!bo->kfd_bo->is_imported)
> > > > +		unreserve_mem_limit(adev, size, alloc_flags);
> > > >    	kfree(bo->kfd_bo);
> > > >    }
> > > > @@ -784,6 +785,24 @@ kfd_mem_dmaunmap_attachment(struct kgd_mem *mem,
> > > >    	}
> > > >    }
> > > > +static struct drm_gem_object*
> > > > +amdgpu_amdkfd_import(struct drm_device *dev, struct dma_buf *dma_buf)
> > > > +{
> > > > +	struct drm_gem_object *gobj;
> > > > +	struct amdgpu_bo *abo;
> > > > +
> > > > +	if (dma_buf->ops == &amdgpu_dmabuf_ops) {
> > > I'd rather remove this limitation. We should be able to use any DMABuf with
> > > KFD. This check was added when we basically sidestepped all the dmabuf
> > > attachment code and just extracted the amdgpu_bo ourselves. I don't think we
> > > want to keep doing that.
> > This limitation here is to just reference the gobj if it is an amdgpu bo
> > and from same device instead of creating a gobj when importing a dmabuf.
> > 
> > > Please see my patch "[PATCH v2 1/2] drm/amdgpu: Generalize KFD dmabuf
> > > import" sent to amd-gfx on March 16. I'm about to send an updated version of
> > > this as part of upstream RDMA support soon.
> > The "drm/amdgpu: Generalize KFD dmabuf import" doesn't handle the struct kgd_mem
> > memory leak issue. Looking forward to the updated version. Thanks!
> 
> Maybe we're trying to fix different problems. Can you give a more detailed
> explanation of the memory leak you're seeing? It's not obvious to me.

The struct kgd_mem is allocted by "*mem = kzalloc(sizeof(struct kgd_mem), GFP_KERNEL);",
but it is not assigned to bo->kfd_bo like this "bo->kfd_bo = *mem;". Then *mem will 
never be freed.

Regards,
Lang

> The problem I'm trying to solve is, to ensure that each exported BO only has
> a single dmabuf because we run into problems with GEM if we have multiple
> dmabufs pointing to the same GEM object. That also enables re-exporting
> dmabufs of imported BOs. At the same time I'm removing any limitations of
> the types of BOs we can import, and trying to eliminate any custom dmabuf
> handling in KFD.
> 
> Regards,
>   Felix
> 
> 
> > 
> > Regards,
> > Lang
> > 
> > > Regards,
> > >    Felix
> > > 
> > > 
> > > > +		gobj = dma_buf->priv;
> > > > +		abo = gem_to_amdgpu_bo(gobj);
> > > > +		if (gobj->dev == dev && abo->kfd_bo) {
> > > > +			drm_gem_object_get(gobj);
> > > > +			return gobj;
> > > > +		}
> > > > +	}
> > > > +
> > > > +	return amdgpu_dma_buf_create_obj_and_attach(dev, dma_buf);
> > > > +}
> > > > +
> > > >    static int
> > > >    kfd_mem_attach_dmabuf(struct amdgpu_device *adev, struct kgd_mem *mem,
> > > >    		      struct amdgpu_bo **bo)
> > > > @@ -802,7 +821,7 @@ kfd_mem_attach_dmabuf(struct amdgpu_device *adev, struct kgd_mem *mem,
> > > >    		}
> > > >    	}
> > > > -	gobj = amdgpu_gem_prime_import(adev_to_drm(adev), mem->dmabuf);
> > > > +	gobj = amdgpu_amdkfd_import(adev_to_drm(adev), mem->dmabuf);
> > > >    	if (IS_ERR(gobj))
> > > >    		return PTR_ERR(gobj);
> > > > @@ -1805,12 +1824,13 @@ int amdgpu_amdkfd_gpuvm_free_memory_of_gpu(
> > > >    {
> > > >    	struct amdkfd_process_info *process_info = mem->process_info;
> > > >    	unsigned long bo_size = mem->bo->tbo.base.size;
> > > > +	bool is_imported = false;
> > > > +	struct drm_gem_object *imported_gobj;
> > > >    	struct kfd_mem_attachment *entry, *tmp;
> > > >    	struct bo_vm_reservation_context ctx;
> > > >    	struct ttm_validate_buffer *bo_list_entry;
> > > >    	unsigned int mapped_to_gpu_memory;
> > > >    	int ret;
> > > > -	bool is_imported = false;
> > > >    	mutex_lock(&mem->lock);
> > > > @@ -1885,7 +1905,13 @@ int amdgpu_amdkfd_gpuvm_free_memory_of_gpu(
> > > >    	}
> > > >    	/* Free the BO*/
> > > > -	drm_vma_node_revoke(&mem->bo->tbo.base.vma_node, drm_priv);
> > > > +	if (!is_imported) {
> > > > +		drm_vma_node_revoke(&mem->bo->tbo.base.vma_node, drm_priv);
> > > > +	} else {
> > > > +		imported_gobj = mem->dmabuf->priv;
> > > > +		drm_vma_node_revoke(&imported_gobj->vma_node, drm_priv);
> > > > +	}
> > > > +
> > > >    	if (mem->dmabuf)
> > > >    		dma_buf_put(mem->dmabuf);
> > > >    	mutex_destroy(&mem->lock);
> > > > @@ -2249,62 +2275,77 @@ int amdgpu_amdkfd_gpuvm_import_dmabuf(struct amdgpu_device *adev,
> > > >    				      uint64_t *mmap_offset)
> > > >    {
> > > >    	struct amdgpu_vm *avm = drm_priv_to_vm(drm_priv);
> > > > -	struct drm_gem_object *obj;
> > > > -	struct amdgpu_bo *bo;
> > > > +	struct drm_gem_object *imported_gobj, *gobj;
> > > > +	struct amdgpu_bo *imported_bo, *bo;
> > > >    	int ret;
> > > > -	if (dma_buf->ops != &amdgpu_dmabuf_ops)
> > > > -		/* Can't handle non-graphics buffers */
> > > > +	/*
> > > > +	 * Can't handle non-graphics buffers and
> > > > +	 * buffers from other devices
> > > > +	 */
> > > > +	imported_gobj = dma_buf->priv;
> > > > +	if (dma_buf->ops != &amdgpu_dmabuf_ops ||
> > > > +	    drm_to_adev(imported_gobj->dev) != adev)
> > > >    		return -EINVAL;
> > > > -	obj = dma_buf->priv;
> > > > -	if (drm_to_adev(obj->dev) != adev)
> > > > -		/* Can't handle buffers from other devices */
> > > > +	/* Only VRAM and GTT BOs are supported */
> > > > +	imported_bo = gem_to_amdgpu_bo(imported_gobj);
> > > > +	if (!(imported_bo->preferred_domains &
> > > > +	    (AMDGPU_GEM_DOMAIN_VRAM | AMDGPU_GEM_DOMAIN_GTT)))
> > > >    		return -EINVAL;
> > > > -	bo = gem_to_amdgpu_bo(obj);
> > > > -	if (!(bo->preferred_domains & (AMDGPU_GEM_DOMAIN_VRAM |
> > > > -				    AMDGPU_GEM_DOMAIN_GTT)))
> > > > -		/* Only VRAM and GTT BOs are supported */
> > > > -		return -EINVAL;
> > > > +	ret = drm_vma_node_allow(&imported_gobj->vma_node, drm_priv);
> > > > +	if (ret)
> > > > +		return ret;
> > > > -	*mem = kzalloc(sizeof(struct kgd_mem), GFP_KERNEL);
> > > > -	if (!*mem)
> > > > -		return -ENOMEM;
> > > > +	gobj = amdgpu_amdkfd_import(adev_to_drm(adev), dma_buf);
> > > > +	if (IS_ERR(gobj)) {
> > > > +		ret = PTR_ERR(gobj);
> > > > +		goto err_import;
> > > > +	}
> > > > -	ret = drm_vma_node_allow(&obj->vma_node, drm_priv);
> > > > -	if (ret) {
> > > > -		kfree(mem);
> > > > -		return ret;
> > > > +	bo = gem_to_amdgpu_bo(gobj);
> > > > +	bo->flags |= AMDGPU_GEM_CREATE_PREEMPTIBLE;
> > > > +
> > > > +	*mem = kzalloc(sizeof(struct kgd_mem), GFP_KERNEL);
> > > > +	if (!*mem) {
> > > > +		ret = -ENOMEM;
> > > > +		goto err_alloc_mem;
> > > >    	}
> > > >    	if (size)
> > > > -		*size = amdgpu_bo_size(bo);
> > > > +		*size = amdgpu_bo_size(imported_bo);
> > > >    	if (mmap_offset)
> > > > -		*mmap_offset = amdgpu_bo_mmap_offset(bo);
> > > > +		*mmap_offset = amdgpu_bo_mmap_offset(imported_bo);
> > > >    	INIT_LIST_HEAD(&(*mem)->attachments);
> > > >    	mutex_init(&(*mem)->lock);
> > > >    	(*mem)->alloc_flags =
> > > > -		((bo->preferred_domains & AMDGPU_GEM_DOMAIN_VRAM) ?
> > > > +		((imported_bo->preferred_domains & AMDGPU_GEM_DOMAIN_VRAM) ?
> > > >    		KFD_IOC_ALLOC_MEM_FLAGS_VRAM : KFD_IOC_ALLOC_MEM_FLAGS_GTT)
> > > >    		| KFD_IOC_ALLOC_MEM_FLAGS_WRITABLE
> > > >    		| KFD_IOC_ALLOC_MEM_FLAGS_EXECUTABLE;
> > > > -	drm_gem_object_get(&bo->tbo.base);
> > > > +	get_dma_buf(dma_buf);
> > > > +	(*mem)->dmabuf = dma_buf;
> > > >    	(*mem)->bo = bo;
> > > >    	(*mem)->va = va;
> > > > -	(*mem)->domain = (bo->preferred_domains & AMDGPU_GEM_DOMAIN_VRAM) ?
> > > > -		AMDGPU_GEM_DOMAIN_VRAM : AMDGPU_GEM_DOMAIN_GTT;
> > > > +	(*mem)->domain = AMDGPU_GEM_DOMAIN_GTT;
> > > >    	(*mem)->mapped_to_gpu_memory = 0;
> > > >    	(*mem)->process_info = avm->process_info;
> > > >    	add_kgd_mem_to_kfd_bo_list(*mem, avm->process_info, false);
> > > >    	amdgpu_sync_create(&(*mem)->sync);
> > > >    	(*mem)->is_imported = true;
> > > > +	bo->kfd_bo = *mem;
> > > >    	return 0;
> > > > +err_import:
> > > > +	drm_vma_node_revoke(&imported_gobj->vma_node, drm_priv);
> > > > +err_alloc_mem:
> > > > +	drm_gem_object_put(gobj);
> > > > +	return ret;
> > > >    }
> > > >    /* Evict a userptr BO by stopping the queues if necessary