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Message-ID: <2806a097-1a8f-595c-fad8-6cb7ec5f4172@gmail.com>
Date:   Fri, 19 May 2023 12:09:34 -0500
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Subject: Re: [PATCH for-next v5 5/7] RDMA/rxe: Allow registering MRs for
 On-Demand Paging
Content-Language: en-US
To:     Daisuke Matsuda <matsuda-daisuke@fujitsu.com>,
        linux-rdma@vger.kernel.org, leonro@nvidia.com, jgg@nvidia.com,
        zyjzyj2000@gmail.com
Cc:     linux-kernel@vger.kernel.org, yangx.jy@fujitsu.com,
        lizhijian@fujitsu.com, y-goto@fujitsu.com
References: <cover.1684397037.git.matsuda-daisuke@fujitsu.com>
 <7d8595c23e954e0fdc19b14e95da13ceef2adafd.1684397037.git.matsuda-daisuke@fujitsu.com>
From:   Bob Pearson <rpearsonhpe@gmail.com>
In-Reply-To: <7d8595c23e954e0fdc19b14e95da13ceef2adafd.1684397037.git.matsuda-daisuke@fujitsu.com>
Content-Type: text/plain; charset=UTF-8
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Precedence: bulk

On 5/18/23 03:21, Daisuke Matsuda wrote:
> Allow applications to register an ODP-enabled MR, in which case the flag
> IB_ACCESS_ON_DEMAND is passed to rxe_reg_user_mr(). However, there is no
> RDMA operation supported right now. They will be enabled later in the
> subsequent two patches.
> 
> rxe_odp_do_pagefault() is called to initialize an ODP-enabled MR. It syncs
> process address space from the CPU page table to the driver page table
> (dma_list/pfn_list in umem_odp) when called with RXE_PAGEFAULT_SNAPSHOT
> flag. Additionally, It can be used to trigger page fault when pages being
> accessed are not present or do not have proper read/write permissions, and
> possibly to prefetch pages in the future.
> 
> Signed-off-by: Daisuke Matsuda <matsuda-daisuke@fujitsu.com>
> ---
>  drivers/infiniband/sw/rxe/rxe.c       |   7 ++
>  drivers/infiniband/sw/rxe/rxe_loc.h   |  14 +++
>  drivers/infiniband/sw/rxe/rxe_mr.c    |   9 +-
>  drivers/infiniband/sw/rxe/rxe_odp.c   | 120 ++++++++++++++++++++++++++
>  drivers/infiniband/sw/rxe/rxe_resp.c  |  15 +++-
>  drivers/infiniband/sw/rxe/rxe_verbs.c |   5 +-
>  drivers/infiniband/sw/rxe/rxe_verbs.h |   2 +
>  7 files changed, 166 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/rxe/rxe.c b/drivers/infiniband/sw/rxe/rxe.c
> index 54c723a6edda..f2284d27229b 100644
> --- a/drivers/infiniband/sw/rxe/rxe.c
> +++ b/drivers/infiniband/sw/rxe/rxe.c
> @@ -73,6 +73,13 @@ static void rxe_init_device_param(struct rxe_dev *rxe)
>  			rxe->ndev->dev_addr);
>  
>  	rxe->max_ucontext			= RXE_MAX_UCONTEXT;
> +
> +	if (IS_ENABLED(CONFIG_INFINIBAND_ON_DEMAND_PAGING)) {
> +		rxe->attr.kernel_cap_flags |= IBK_ON_DEMAND_PAGING;
> +
> +		/* IB_ODP_SUPPORT_IMPLICIT is not supported right now. */
> +		rxe->attr.odp_caps.general_caps |= IB_ODP_SUPPORT;
> +	}
>  }
>  
>  /* initialize port attributes */
> diff --git a/drivers/infiniband/sw/rxe/rxe_loc.h b/drivers/infiniband/sw/rxe/rxe_loc.h
> index 00fedd1a4980..93247d123642 100644
> --- a/drivers/infiniband/sw/rxe/rxe_loc.h
> +++ b/drivers/infiniband/sw/rxe/rxe_loc.h
> @@ -202,4 +202,18 @@ static inline unsigned int wr_opcode_mask(int opcode, struct rxe_qp *qp)
>  	return rxe_wr_opcode_info[opcode].mask[qp->ibqp.qp_type];
>  }
>  
> +/* rxe_odp.c */
> +#ifdef CONFIG_INFINIBAND_ON_DEMAND_PAGING
> +int rxe_odp_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length,
> +			 u64 iova, int access_flags, struct rxe_mr *mr);
> +#else /* CONFIG_INFINIBAND_ON_DEMAND_PAGING */
> +static inline int
> +rxe_odp_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length, u64 iova,
> +		     int access_flags, struct rxe_mr *mr)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +#endif /* CONFIG_INFINIBAND_ON_DEMAND_PAGING */
> +
>  #endif /* RXE_LOC_H */
> diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
> index ffbac6f5e828..cd368cd096c8 100644
> --- a/drivers/infiniband/sw/rxe/rxe_mr.c
> +++ b/drivers/infiniband/sw/rxe/rxe_mr.c
> @@ -318,7 +318,10 @@ int rxe_mr_copy(struct rxe_mr *mr, u64 iova, void *addr,
>  		return err;
>  	}
>  
> -	return rxe_mr_copy_xarray(mr, iova, addr, length, dir);
> +	if (mr->odp_enabled)
> +		return -EOPNOTSUPP;
> +	else
> +		return rxe_mr_copy_xarray(mr, iova, addr, length, dir);
>  }
>  
>  /* copy data in or out of a wqe, i.e. sg list
> @@ -527,6 +530,10 @@ int rxe_mr_do_atomic_write(struct rxe_mr *mr, u64 iova, u64 value)
>  	struct page *page;
>  	u64 *va;
>  
> +	/* ODP is not supported right now. WIP. */
> +	if (mr->odp_enabled)
> +		return RESPST_ERR_UNSUPPORTED_OPCODE;
> +
>  	/* See IBA oA19-28 */
>  	if (unlikely(mr->state != RXE_MR_STATE_VALID)) {
>  		rxe_dbg_mr(mr, "mr not in valid state");
> diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c b/drivers/infiniband/sw/rxe/rxe_odp.c
> index b69b25e0fef6..e5497d09c399 100644
> --- a/drivers/infiniband/sw/rxe/rxe_odp.c
> +++ b/drivers/infiniband/sw/rxe/rxe_odp.c
> @@ -24,6 +24,24 @@ static void rxe_mr_unset_xarray(struct rxe_mr *mr, unsigned long start,
>  	spin_unlock(&mr->page_list.xa_lock);
>  }
>  
> +static void rxe_mr_set_xarray(struct rxe_mr *mr, unsigned long start,
> +			      unsigned long end, unsigned long *pfn_list)
> +{
> +	unsigned long lower, upper, idx;
> +	struct page *page;
> +
> +	lower = rxe_mr_iova_to_index(mr, start);
> +	upper = rxe_mr_iova_to_index(mr, end);
> +
> +	/* make pages visible in xarray. no sleep while taking the lock */
> +	spin_lock(&mr->page_list.xa_lock);
> +	for (idx = lower; idx <= upper; idx++) {
> +		page = hmm_pfn_to_page(pfn_list[idx]);
> +		__xa_store(&mr->page_list, idx, page, GFP_ATOMIC);
> +	}
> +	spin_unlock(&mr->page_list.xa_lock);
> +}
> +
>  static bool rxe_ib_invalidate_range(struct mmu_interval_notifier *mni,
>  				    const struct mmu_notifier_range *range,
>  				    unsigned long cur_seq)
> @@ -54,3 +72,105 @@ static bool rxe_ib_invalidate_range(struct mmu_interval_notifier *mni,
>  const struct mmu_interval_notifier_ops rxe_mn_ops = {
>  	.invalidate = rxe_ib_invalidate_range,
>  };
> +
> +#define RXE_PAGEFAULT_RDONLY BIT(1)
> +#define RXE_PAGEFAULT_SNAPSHOT BIT(2)
> +static int rxe_odp_do_pagefault(struct rxe_mr *mr, u64 user_va, int bcnt, u32 flags)
> +{
> +	int np;
> +	u64 access_mask;
> +	bool fault = !(flags & RXE_PAGEFAULT_SNAPSHOT);
> +	struct ib_umem_odp *umem_odp = to_ib_umem_odp(mr->umem);
> +
> +	access_mask = ODP_READ_ALLOWED_BIT;
> +	if (umem_odp->umem.writable && !(flags & RXE_PAGEFAULT_RDONLY))
> +		access_mask |= ODP_WRITE_ALLOWED_BIT;
> +
> +	/*
> +	 * ib_umem_odp_map_dma_and_lock() locks umem_mutex on success.
> +	 * Callers must release the lock later to let invalidation handler
> +	 * do its work again.
> +	 */
> +	np = ib_umem_odp_map_dma_and_lock(umem_odp, user_va, bcnt,
> +					  access_mask, fault);
> +	if (np < 0)
> +		return np;
> +
> +	/* umem_mutex is still locked here, so we can use hmm_pfn_to_page()
> +	 * safely to fetch pages in the range.
> +	 */
> +	rxe_mr_set_xarray(mr, user_va, user_va + bcnt, umem_odp->pfn_list);
> +
> +	return np;
> +}
> +
> +static int rxe_odp_init_pages(struct rxe_mr *mr)
> +{
> +	int ret;
> +	struct ib_umem_odp *umem_odp = to_ib_umem_odp(mr->umem);
> +
> +	ret = rxe_odp_do_pagefault(mr, mr->umem->address, mr->umem->length,
> +				   RXE_PAGEFAULT_SNAPSHOT);
> +
> +	if (ret >= 0)
> +		mutex_unlock(&umem_odp->umem_mutex);
> +
> +	return ret >= 0 ? 0 : ret;
> +}
> +
> +int rxe_odp_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length,
> +			 u64 iova, int access_flags, struct rxe_mr *mr)
> +{
> +	int err;
> +	struct ib_umem_odp *umem_odp;
> +
> +	if (!IS_ENABLED(CONFIG_INFINIBAND_ON_DEMAND_PAGING))
> +		return -EOPNOTSUPP;
> +
> +	rxe_mr_init(access_flags, mr);
> +
> +	xa_init(&mr->page_list);
> +
> +	if (!start && length == U64_MAX) {
> +		if (iova != 0)
> +			return -EINVAL;
> +		if (!(rxe->attr.odp_caps.general_caps & IB_ODP_SUPPORT_IMPLICIT))
> +			return -EINVAL;
> +
> +		/* Never reach here, for implicit ODP is not implemented. */
> +	}
> +
> +	umem_odp = ib_umem_odp_get(&rxe->ib_dev, start, length, access_flags,
> +				   &rxe_mn_ops);
> +	if (IS_ERR(umem_odp)) {
> +		rxe_dbg_mr(mr, "Unable to create umem_odp err = %d\n",
> +			   (int)PTR_ERR(umem_odp));
> +		return PTR_ERR(umem_odp);
> +	}
> +
> +	umem_odp->private = mr;
> +
> +	mr->odp_enabled = true;
> +	mr->umem = &umem_odp->umem;
> +	mr->access = access_flags;
> +	mr->ibmr.length = length;
> +	mr->ibmr.iova = iova;
> +	mr->page_offset = ib_umem_offset(&umem_odp->umem);
> +
> +	err = rxe_odp_init_pages(mr);
> +	if (err) {
> +		ib_umem_odp_release(umem_odp);
> +		return err;
> +	}
> +
> +	err = rxe_mr_fill_pages_from_sgt(mr, &umem_odp->umem.sgt_append.sgt);
> +	if (err) {
> +		ib_umem_odp_release(umem_odp);
> +		return err;
> +	}
> +
> +	mr->state = RXE_MR_STATE_VALID;
> +	mr->ibmr.type = IB_MR_TYPE_USER;
> +
> +	return err;
> +}
> diff --git a/drivers/infiniband/sw/rxe/rxe_resp.c b/drivers/infiniband/sw/rxe/rxe_resp.c
> index ba0222bfce9e..90c31c4f2944 100644
> --- a/drivers/infiniband/sw/rxe/rxe_resp.c
> +++ b/drivers/infiniband/sw/rxe/rxe_resp.c
> @@ -626,6 +626,10 @@ static enum resp_states process_flush(struct rxe_qp *qp,
>  	struct rxe_mr *mr = qp->resp.mr;
>  	struct resp_res *res = qp->resp.res;
>  
> +	/* ODP is not supported right now. WIP. */
> +	if (mr->odp_enabled)
> +		return RESPST_ERR_UNSUPPORTED_OPCODE;
> +
>  	/* oA19-14, oA19-15 */
>  	if (res && res->replay)
>  		return RESPST_ACKNOWLEDGE;
> @@ -679,10 +683,13 @@ static enum resp_states atomic_reply(struct rxe_qp *qp,
>  	if (!res->replay) {
>  		u64 iova = qp->resp.va + qp->resp.offset;
>  
> -		err = rxe_mr_do_atomic_op(mr, iova, pkt->opcode,
> -					  atmeth_comp(pkt),
> -					  atmeth_swap_add(pkt),
> -					  &res->atomic.orig_val);
> +		if (mr->odp_enabled)
> +			err = RESPST_ERR_UNSUPPORTED_OPCODE;
> +		else
> +			err = rxe_mr_do_atomic_op(mr, iova, pkt->opcode,
> +						  atmeth_comp(pkt),
> +						  atmeth_swap_add(pkt),
> +						  &res->atomic.orig_val);
>  		if (err)
>  			return err;
>  
> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
> index dea605b7f683..9c23defdc7b5 100644
> --- a/drivers/infiniband/sw/rxe/rxe_verbs.c
> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
> @@ -1274,7 +1274,10 @@ static struct ib_mr *rxe_reg_user_mr(struct ib_pd *ibpd, u64 start,
>  	mr->ibmr.pd = ibpd;
>  	mr->ibmr.device = ibpd->device;
>  
> -	err = rxe_mr_init_user(rxe, start, length, iova, access, mr);
> +	if (access & IB_ACCESS_ON_DEMAND)
> +		err = rxe_odp_mr_init_user(rxe, start, length, iova, access, mr);
> +	else
> +		err = rxe_mr_init_user(rxe, start, length, iova, access, mr);
>  	if (err) {
>  		rxe_dbg_mr(mr, "reg_user_mr failed, err = %d", err);
>  		goto err_cleanup;
> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.h b/drivers/infiniband/sw/rxe/rxe_verbs.h
> index b6fbd9b3d086..de5a982c7c7e 100644
> --- a/drivers/infiniband/sw/rxe/rxe_verbs.h
> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.h
> @@ -333,6 +333,8 @@ struct rxe_mr {
>  	u32			nbuf;
>  
>  	struct xarray		page_list;
> +
> +	bool			odp_enabled;
>  };
>  
>  static inline unsigned int mr_page_size(struct rxe_mr *mr)

Reviewed-by: Bob Pearson <rpearsonhpe@gmail.com>