Re: [PATCH v10 4/6] RDMA/mlx5: Support dma-buf based userspace memory region
On Fri, Nov 13, 2020 at 03:51:20AM +, Xiong, Jianxin wrote:
> > > +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(>dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key));
> > > +
> > > + /* Wait for all running page-fault handlers to finish. */
> > > + synchronize_srcu(>dev->odp_srcu);
> > > +
> > > + wait_event(mr->q_deferred_work,
> > > +!atomic_read(>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, >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.
I think you should put the calls to dma_buf_dynamic_attach() and
dma_buf_detach() into mlx5, it makes the whole thing a little cleaner,
then the umem->private isn't needed any more either.
Jason
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RE: [PATCH v10 4/6] RDMA/mlx5: Support dma-buf based userspace memory region
> -Original Message-
> From: Jason Gunthorpe
> Sent: Friday, November 13, 2020 5:06 AM
> To: Xiong, Jianxin
> Cc: linux-r...@vger.kernel.org; dri-devel@lists.freedesktop.org; Doug Ledford
> ; Leon Romanovsky
> ; Sumit Semwal ; Christian Koenig
> ; Vetter, Daniel
>
> Subject: Re: [PATCH v10 4/6] RDMA/mlx5: Support dma-buf based userspace
> memory region
>
> On Fri, Nov 13, 2020 at 03:51:20AM +, Xiong, Jianxin wrote:
>
> > > > +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(>dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key));
> > > > +
> > > > + /* Wait for all running page-fault handlers to finish. */
> > > > + synchronize_srcu(>dev->odp_srcu);
> > > > +
> > > > + wait_event(mr->q_deferred_work,
> > > > +!atomic_read(>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, >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.
>
> I think you should put the calls to dma_buf_dynamic_attach() and
> dma_buf_detach() into mlx5, it makes the whole thing a little cleaner, then
> the umem->private isn't needed any more either.
Putting these calls into mlx5 can remove the 'ops' parameter from the umem_get
call,
but I don't see how umem->private can be eliminated. In addition, I feel
keeping these
two calls in the core provides a better separation between the core and the
driver --
dma-buf API functions are only called from the core, except for
locking/unlocking.
The 'if (mr)' part in the callback can be removed by adding a line
'if (!umem_dmabutf->sgt) return;' before that if that makes a difference.
>
> Jason
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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() |
> 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.
> +/**
> + * 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(>dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key));
> +
> + /* Wait for all running page-fault handlers to finish. */
> + synchronize_srcu(>dev->odp_srcu);
> +
> + wait_event(mr->q_deferred_work, !atomic_read(>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, >mmkey);
> + WARN_ON(mr->descs);
> + }
I didn't check carefully, but are you sure this destroy_mkey should be
here??
Jason
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RE: [PATCH v10 4/6] RDMA/mlx5: Support dma-buf based userspace memory region
> -Original Message-
> From: Jason Gunthorpe
> Sent: Thursday, November 12, 2020 4:40 PM
> To: Xiong, Jianxin
> Cc: linux-r...@vger.kernel.org; dri-devel@lists.freedesktop.org; Doug Ledford
> ; Leon Romanovsky
> ; Sumit Semwal ; Christian Koenig
> ; Vetter, Daniel
>
> 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() |
> > 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(>dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key));
> > +
> > + /* Wait for all running page-fault handlers to finish. */
> > + synchronize_srcu(>dev->odp_srcu);
> > +
> > + wait_event(mr->q_deferred_work,
> > +!atomic_read(>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, >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
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