Re: [PATCH v2 05/15] IB/pvrdma: Add UAR support

[Yuval Shaia <yuval.shaia-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

On Tue, Jul 12, 2016 at 12:36:35PM -0700, Adit Ranadive wrote:
> This patch adds the UAR support for the paravirtual RDMA device. The UAR
> pages are MMIO pages from the virtual PCI space. We define offsets within
> this page to provide the fast data-path operations.
> 
> Reviewed-by: Jorgen Hansen <jhansen-pghWNbHTmq7QT0dZR+AlfA@public.gmane.org>
> Reviewed-by: George Zhang <georgezhang-pghWNbHTmq7QT0dZR+AlfA@public.gmane.org>
> Reviewed-by: Aditya Sarwade <asarwade-pghWNbHTmq7QT0dZR+AlfA@public.gmane.org>
> Reviewed-by: Bryan Tan <bryantan-pghWNbHTmq7QT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Adit Ranadive <aditr-pghWNbHTmq7QT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/infiniband/hw/pvrdma/pvrdma_doorbell.c | 128 +++++++++++++++++++++++++
>  1 file changed, 128 insertions(+)
>  create mode 100644 drivers/infiniband/hw/pvrdma/pvrdma_doorbell.c
> 
> diff --git a/drivers/infiniband/hw/pvrdma/pvrdma_doorbell.c b/drivers/infiniband/hw/pvrdma/pvrdma_doorbell.c
> new file mode 100644
> index 0000000..d854f6d
> --- /dev/null
> +++ b/drivers/infiniband/hw/pvrdma/pvrdma_doorbell.c
> @@ -0,0 +1,128 @@
> +/*
> + * Copyright (c) 2012-2016 VMware, Inc.  All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of EITHER the GNU General Public License
> + * version 2 as published by the Free Software Foundation or the BSD
> + * 2-Clause License. This program is distributed in the hope that it
> + * will be useful, but WITHOUT ANY WARRANTY; WITHOUT EVEN THE IMPLIED
> + * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
> + * See the GNU General Public License version 2 for more details at
> + * http://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program available in the file COPYING in the main
> + * directory of this source tree.
> + *
> + * The BSD 2-Clause License
> + *
> + *     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.
> + *
> + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
> + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
> + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
> + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
> + * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
> + * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
> + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
> + * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
> + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
> + * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
> + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
> + * OF THE POSSIBILITY OF SUCH DAMAGE.
> + */
> +
> +#include <linux/bitmap.h>
> +#include <linux/errno.h>
> +#include <linux/slab.h>
> +
> +#include "pvrdma.h"
> +
> +int pvrdma_uar_table_init(struct pvrdma_dev *dev)
> +{
> +	u32 num = dev->dsr->caps.max_uar;
> +	u32 mask = num - 1;
> +	struct pvrdma_id_table *tbl = &dev->uar_table.tbl;
> +
> +	/* Power of 2 */
> +	if (num != 1 << (ffs(num) - 1))
> +		return -EINVAL;
> +
> +	tbl->last = 0;
> +	tbl->top = 0;
> +	tbl->max = num;
> +	tbl->mask = mask;
> +	spin_lock_init(&tbl->lock);
> +	tbl->table = kcalloc(BITS_TO_LONGS(num), sizeof(long), GFP_KERNEL);
> +	if (!tbl->table)
> +		return -ENOMEM;
> +
> +	/* 0th UAR is taken by the device. */
> +	set_bit(0, tbl->table);
> +
> +	return 0;
> +}
> +
> +void pvrdma_uar_table_cleanup(struct pvrdma_dev *dev)
> +{
> +	struct pvrdma_id_table *tbl = &dev->uar_table.tbl;
> +
> +	kfree(tbl->table);
> +}
> +
> +int pvrdma_uar_alloc(struct pvrdma_dev *dev, struct pvrdma_uar_map *uar)
> +{
> +	struct pvrdma_id_table *tbl;
> +	unsigned long flags;
> +	u32 obj;
> +
> +	tbl = &dev->uar_table.tbl;
> +
> +	spin_lock_irqsave(&tbl->lock, flags);
> +	obj = find_next_zero_bit(tbl->table, tbl->max, tbl->last);
> +	if (obj >= tbl->max) {
> +		tbl->top = (tbl->top + tbl->max) & tbl->mask;
> +		obj = find_first_zero_bit(tbl->table, tbl->max);
> +	}
> +
> +	if (obj < tbl->max) {
> +		set_bit(obj, tbl->table);
> +		obj |= tbl->top;
> +	} else {
> +		spin_unlock_irqrestore(&tbl->lock, flags);
> +		return -ENOMEM;
> +	}

Please consider restructuring the above block to something like this:
	if (obj >= tbl->max) {
		spin_unlock_irqrestore(&tbl->lock, flags);
		return -ENOMEM;
	}

	set_bit(obj, tbl->table);
	obj |= tbl->top;

> +
> +	spin_unlock_irqrestore(&tbl->lock, flags);
> +
> +	uar->index = obj;
> +	uar->pfn = (pci_resource_start(dev->pdev, PVRDMA_PCI_RESOURCE_UAR) >>
> +		    PAGE_SHIFT) + uar->index;
> +
> +	return 0;
> +}
> +
> +void pvrdma_uar_free(struct pvrdma_dev *dev, struct pvrdma_uar_map *uar)
> +{
> +	struct pvrdma_id_table *tbl = &dev->uar_table.tbl;
> +	unsigned long flags;
> +	u32 obj;
> +
> +	obj = uar->index & (tbl->max - 1);
> +	spin_lock_irqsave(&tbl->lock, flags);
> +	clear_bit(obj, tbl->table);
> +	tbl->last = min(tbl->last, obj);
> +	tbl->top = (tbl->top + tbl->max) & tbl->mask;
> +	spin_unlock_irqrestore(&tbl->lock, flags);
> +}
> -- 
> 2.7.4
> 
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