Re: [RFC PATCH 2/2] RDMA/efa: Add support for dmabuf memory regions

[Gal Pressman <galpress@amazon.com>]

On 07/10/2021 14:40, Jason Gunthorpe wrote:
> On Thu, Oct 07, 2021 at 01:43:00PM +0300, Gal Pressman wrote:
> 
>> @@ -1491,26 +1493,29 @@ static int efa_create_pbl(struct efa_dev *dev,
>>  	return 0;
>>  }
>>  
>> -struct ib_mr *efa_reg_mr(struct ib_pd *ibpd, u64 start, u64 length,
>> -			 u64 virt_addr, int access_flags,
>> -			 struct ib_udata *udata)
>> +static void efa_dmabuf_invalidate_cb(struct dma_buf_attachment *attach)
>> +{
>> +	WARN_ON_ONCE(1,
>> +		     "Invalidate callback should not be called when memory is pinned\n");
>> +}
>> +
>> +static struct dma_buf_attach_ops efa_dmabuf_attach_ops = {
>> +	.allow_peer2peer = true,
>> +	.move_notify = efa_dmabuf_invalidate_cb,
>> +};
> 
> Shouldn't move_notify really just be left as NULL? I mean fixing
> whatever is preventing that?

That's what I had in the previous RFC and I think Christian didn't really like it.

>> +struct ib_mr *efa_reg_user_mr_dmabuf(struct ib_pd *ibpd, u64 start,
>> +				     u64 length, u64 virt_addr,
>> +				     int fd, int access_flags,
>> +				     struct ib_udata *udata)
>> +{
>> +	struct efa_dev *dev = to_edev(ibpd->device);
>> +	struct ib_umem_dmabuf *umem_dmabuf;
>> +	struct efa_mr *mr;
>> +	int err;
>> +
>> +	mr = efa_alloc_mr(ibpd, access_flags, udata);
>> +	if (IS_ERR(mr)) {
>> +		err = PTR_ERR(mr);
>> +		goto err_out;
>> +	}
>> +
>> +	umem_dmabuf = ib_umem_dmabuf_get(ibpd->device, start, length, fd,
>> +					 access_flags, &efa_dmabuf_attach_ops);
>> +	if (IS_ERR(umem_dmabuf)) {
>> +		ibdev_dbg(&dev->ibdev, "Failed to get dmabuf[%d]\n", err);
>> +		err = PTR_ERR(umem_dmabuf);
>> +		goto err_free;
>> +	}
>> +
>> +	dma_resv_lock(umem_dmabuf->attach->dmabuf->resv, NULL);
>> +	err = dma_buf_pin(umem_dmabuf->attach);
>> +	if (err) {
>> +		ibdev_dbg(&dev->ibdev, "Failed to pin dmabuf memory\n");
>> +		goto err_release;
>> +	}
>> +
>> +	err = ib_umem_dmabuf_map_pages(umem_dmabuf);
>> +	if (err) {
>> +		ibdev_dbg(&dev->ibdev, "Failed to map dmabuf pages\n");
>> +		goto err_unpin;
>> +	}
>> +	dma_resv_unlock(umem_dmabuf->attach->dmabuf->resv);
> 
> If it is really this simple the core code should have this logic,
> 'ib_umem_dmabuf_get_pinned()' or something

Should get_pinned do just get + dma_buf_pin, or should it do
ib_umem_dmabuf_map_pages as well?