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

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Date:   Thu, 7 Oct 2021 08:40:18 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Gal Pressman <galpress@...zon.com>
Cc:     Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Doug Ledford <dledford@...hat.com>,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        Oded Gabbay <ogabbay@...ana.ai>,
        Tomer Tayar <ttayar@...ana.ai>,
        Yossi Leybovich <sleybo@...zon.com>,
        Alexander Matushevsky <matua@...zon.com>,
        Leon Romanovsky <leonro@...dia.com>,
        Jianxin Xiong <jianxin.xiong@...el.com>,
        Firas Jahjah <firasj@...zon.com>
Subject: Re: [RFC PATCH 2/2] RDMA/efa: Add support for dmabuf memory regions

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?

> +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

Jason