> -----Original Message-----
> From: Jason Gunthorpe <jgg@xxxxxxxx>
> Sent: Thursday, November 12, 2020 4:40 PM
> To: Xiong, Jianxin <jianxin.xiong@xxxxxxxxx>
> Cc: linux-rdma@xxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; Doug Ledford <dledford@xxxxxxxxxx>; Leon Romanovsky
> <leon@xxxxxxxxxx>; Sumit Semwal <sumit.semwal@xxxxxxxxxx>; Christian Koenig <christian.koenig@xxxxxxx>; Vetter, Daniel
> <daniel.vetter@xxxxxxxxx>
> Subject: Re: [PATCH v10 4/6] RDMA/mlx5: Support dma-buf based userspace memory region
>
> On Tue, Nov 10, 2020 at 01:41:15PM -0800, Jianxin Xiong wrote:
>
> > -static int mlx5_ib_update_mr_pas(struct mlx5_ib_mr *mr, unsigned int
> > flags)
> > +int mlx5_ib_update_mr_pas(struct mlx5_ib_mr *mr, unsigned int flags)
> > {
> > struct mlx5_ib_dev *dev = mr->dev;
> > struct device *ddev = dev->ib_dev.dev.parent; @@ -1255,6 +1267,10 @@
> > static int mlx5_ib_update_mr_pas(struct mlx5_ib_mr *mr, unsigned int flags)
> > cur_mtt->ptag =
> > cpu_to_be64(rdma_block_iter_dma_address(&biter) |
> > MLX5_IB_MTT_PRESENT);
> > +
> > + if (mr->umem->is_dmabuf && (flags & MLX5_IB_UPD_XLT_ZAP))
> > + cur_mtt->ptag = 0;
> > +
> > cur_mtt++;
> > }
> >
> > @@ -1291,8 +1307,15 @@ static struct mlx5_ib_mr *reg_create(struct ib_mr *ibmr, struct ib_pd *pd,
> > int err;
> > bool pg_cap = !!(MLX5_CAP_GEN(dev->mdev, pg));
> >
> > - page_size =
> > - mlx5_umem_find_best_pgsz(umem, mkc, log_page_size, 0, iova);
> > + if (umem->is_dmabuf) {
> > + if ((iova ^ umem->address) & (PAGE_SIZE - 1))
> > + return ERR_PTR(-EINVAL);
> > + umem->iova = iova;
> > + page_size = PAGE_SIZE;
> > + } else {
> > + page_size = mlx5_umem_find_best_pgsz(umem, mkc, log_page_size,
> > + 0, iova);
> > + }
>
> Urk, maybe this duplicated sequence should be in a function..
>
> This will also collide with a rereg_mr bugfixing series that should be posted soon..
>
> > +static void mlx5_ib_dmabuf_invalidate_cb(struct dma_buf_attachment
> > +*attach) {
> > + struct ib_umem_dmabuf *umem_dmabuf = attach->importer_priv;
> > + struct mlx5_ib_mr *mr = umem_dmabuf->private;
> > +
> > + dma_resv_assert_held(umem_dmabuf->attach->dmabuf->resv);
> > +
> > + if (mr)
>
> I don't think this 'if (mr)' test is needed anymore? I certainly prefer it gone as it is kind of messy. I expect unmapping the dma to ensure this
> function is not running, and won't run again.
It is still needed. When the dma-buf moves, the callback function of every attached importer is invoked, regardless if the importer has mapped the dma or not.
>
> > +/**
> > + * mlx5_ib_fence_dmabuf_mr - Stop all access to the dmabuf MR
> > + * @mr: to fence
> > + *
> > + * On return no parallel threads will be touching this MR and no DMA
> > +will be
> > + * active.
> > + */
> > +void mlx5_ib_fence_dmabuf_mr(struct mlx5_ib_mr *mr) {
> > + struct ib_umem_dmabuf *umem_dmabuf = to_ib_umem_dmabuf(mr->umem);
> > +
> > + /* Prevent new page faults and prefetch requests from succeeding */
> > + xa_erase(&mr->dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key));
> > +
> > + /* Wait for all running page-fault handlers to finish. */
> > + synchronize_srcu(&mr->dev->odp_srcu);
> > +
> > + wait_event(mr->q_deferred_work,
> > +!atomic_read(&mr->num_deferred_work));
> > +
> > + dma_resv_lock(umem_dmabuf->attach->dmabuf->resv, NULL);
> > + mlx5_mr_cache_invalidate(mr);
> > + umem_dmabuf->private = NULL;
> > + ib_umem_dmabuf_unmap_pages(umem_dmabuf);
> > + dma_resv_unlock(umem_dmabuf->attach->dmabuf->resv);
> > +
> > + if (!mr->cache_ent) {
> > + mlx5_core_destroy_mkey(mr->dev->mdev, &mr->mmkey);
> > + WARN_ON(mr->descs);
> > + }
>
> I didn't check carefully, but are you sure this destroy_mkey should be here??
To my understanding, yes. This is similar to what dma_fence_odp_mr() does,
just inlined here since it's not called from other places.
>
> Jason
