linux/drivers/infiniband/hw/mlx5/doorbell.c

/*
 * Copyright (c) 2013-2015, Mellanox Technologies. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <linux/kref.h>
#include <linux/slab.h>
#include <linux/sched/mm.h>
#include <rdma/ib_umem.h>

#include "mlx5_ib.h"

#define MLX5_IB_DBR_SIZE (sizeof(__be32) * 2)

struct mlx5_ib_user_db_page {
	struct list_head	list;
	struct ib_umem	       *umem;
	struct ib_uverbs_buffer_desc desc;
	int			refcnt;
	struct mm_struct	*mm;
};

static int mlx5_ib_db_map_user_desc(struct mlx5_ib_ucontext *context,
				    const struct ib_uverbs_buffer_desc *desc,
				    struct mlx5_db *db)
{
	struct mlx5_ib_user_db_page *page;
	struct ib_umem *umem;
	int err = 0;

	if (desc->length < MLX5_IB_DBR_SIZE)
		return -EINVAL;
	/*
	 * For VA descriptors the umem is normalized to a single PAGE_SIZE
	 * region, so reject offsets that would place the 8-byte DBR
	 * straddling the page boundary.
	 */
	if (desc->type == IB_UVERBS_BUFFER_TYPE_VA &&
	    (desc->addr & ~PAGE_MASK) > PAGE_SIZE - MLX5_IB_DBR_SIZE)
		return -EINVAL;

	mutex_lock(&context->db_page_mutex);

	/*
	 * Only VA-typed descriptors are eligible to share a per-page
	 * doorbell umem; FD-typed descriptors are pinned individually.
	 */
	if (desc->type == IB_UVERBS_BUFFER_TYPE_VA) {
		list_for_each_entry(page, &context->db_page_list, list) {
			if (current->mm != page->mm)
				continue;
			if (page->desc.addr == (desc->addr & PAGE_MASK))
				goto found;
		}
	}

	page = kzalloc_obj(*page);
	if (!page) {
		err = -ENOMEM;
		goto out;
	}

	page->desc = *desc;

	/*
	 * Normalize VA descriptors to a page-aligned PAGE_SIZE region so
	 * multiple DBRs that fall in the same user page share one umem.
	 */
	if (page->desc.type == IB_UVERBS_BUFFER_TYPE_VA) {
		page->desc.addr &= PAGE_MASK;
		page->desc.length = PAGE_SIZE;
	}

	umem = ib_umem_get_desc(context->ibucontext.device, &page->desc, 0);
	if (IS_ERR(umem)) {
		err = PTR_ERR(umem);
		kfree(page);
		goto out;
	}

	/*
	 * The 8-byte DBR is programmed to the device as one DMA address,
	 * so it must live in a single contiguous DMA segment.
	 */
	if (!ib_umem_is_contiguous(umem)) {
		ib_umem_release(umem);
		kfree(page);
		err = -EINVAL;
		goto out;
	}

	page->umem = umem;
	if (page->desc.type == IB_UVERBS_BUFFER_TYPE_VA) {
		mmgrab(current->mm);
		page->mm = current->mm;
	}
	list_add(&page->list, &context->db_page_list);

found:
	db->dma = sg_dma_address(page->umem->sgt_append.sgt.sgl) +
		  (desc->addr & ~PAGE_MASK);
	db->u.user_page = page;
	++page->refcnt;

out:
	mutex_unlock(&context->db_page_mutex);

	return err;
}

int mlx5_ib_db_map_user(struct mlx5_ib_ucontext *context,
			const struct uverbs_attr_bundle *attrs, u16 attr_id,
			unsigned long virt, struct mlx5_db *db)
{
	struct ib_uverbs_buffer_desc desc = {
		.type = IB_UVERBS_BUFFER_TYPE_VA,
		.addr = virt,
		.length = MLX5_IB_DBR_SIZE,
	};

	if (attrs) {
		int err;

		err = uverbs_get_buffer_desc(attrs, attr_id, &desc);
		if (err && err != -ENOENT)
			return err;
	}

	return mlx5_ib_db_map_user_desc(context, &desc, db);
}

void mlx5_ib_db_unmap_user(struct mlx5_ib_ucontext *context, struct mlx5_db *db)
{
	mutex_lock(&context->db_page_mutex);

	if (!--db->u.user_page->refcnt) {
		list_del(&db->u.user_page->list);
		if (db->u.user_page->mm)
			mmdrop(db->u.user_page->mm);
		ib_umem_release(db->u.user_page->umem);
		kfree(db->u.user_page);
	}

	mutex_unlock(&context->db_page_mutex);
}