Subject: Re: [PATCH v5 08/16] IB/pvrdma: Add device command support

From: Yuval Shaia <[email-masked]>
Date: Mon, 26 Sep 2016 10:16:01 +0300

Minor question/suggestion inline.
(sorry for missing it till now).

Yuval

On Sat, Sep 24, 2016 at 04:21:32PM -0700, Adit Ranadive wrote:
> This patch enables posting Verb requests and receiving responses to/from
> the backend PVRDMA emulation layer.
> 
> Reviewed-by: Yuval Shaia <[email-masked]>
> Reviewed-by: Jorgen Hansen <[email-masked]>
> Reviewed-by: George Zhang <[email-masked]>
> Reviewed-by: Aditya Sarwade <[email-masked]>
> Reviewed-by: Bryan Tan <[email-masked]>
> Signed-off-by: Adit Ranadive <[email-masked]>
> ---
> Changes v4->v5:
>  - Moved the timeout to pvrdma_cmd_recv.
>  - Added additional response code parameter to pvrdma_cmd_post.
> 
> Changes v3->v4:
>  - Removed the min check and added a BUILD_BUG_ON check for size.
> 
> Changes v2->v3:
>  - Converted pvrdma_cmd_recv to inline.
>  - Added a min check in the memcpy to cmd_slot.
>  - Removed the boolean from pvrdma_cmd_post.
> ---
>  drivers/infiniband/hw/pvrdma/pvrdma_cmd.c | 117 ++++++++++++++++++++++++++++++
>  1 file changed, 117 insertions(+)
>  create mode 100644 drivers/infiniband/hw/pvrdma/pvrdma_cmd.c
> 
> diff --git a/drivers/infiniband/hw/pvrdma/pvrdma_cmd.c b/drivers/infiniband/hw/pvrdma/pvrdma_cmd.c
> new file mode 100644
> index 0000000..21f1af8
> --- /dev/null
> +++ b/drivers/infiniband/hw/pvrdma/pvrdma_cmd.c
> @@ -0,0 +1,117 @@
> +/*
> + * 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/list.h>
> +
> +#include "pvrdma.h"
> +
> +#define PVRDMA_CMD_TIMEOUT	10000 /* ms */
> +
> +static inline int pvrdma_cmd_recv(struct pvrdma_dev *dev,
> +				  union pvrdma_cmd_resp *resp,
> +				  unsigned resp_code)
> +{
> +	int err;
> +
> +	dev_dbg(&dev->pdev->dev, "receive response from device\n");
> +
> +	err = wait_for_completion_interruptible_timeout(&dev->cmd_done,
> +			msecs_to_jiffies(PVRDMA_CMD_TIMEOUT));
> +	if (err == 0 || err == -ERESTARTSYS) {
> +		dev_warn(&dev->pdev->dev,
> +			 "completion timeout or interrupted\n");
> +		return -ETIMEDOUT;
> +	}
> +
> +	spin_lock(&dev->cmd_lock);
> +	memcpy(resp, dev->resp_slot, sizeof(*resp));
> +	spin_unlock(&dev->cmd_lock);
> +
> +	if (resp->hdr.ack != resp_code) {
> +		dev_warn(&dev->pdev->dev,
> +			 "unknown response %#x expected %#x\n",
> +			 resp->hdr.ack, resp_code);
> +		return -EFAULT;
> +	}
> +
> +	return 0;
> +}
> +
> +int
> +pvrdma_cmd_post(struct pvrdma_dev *dev, union pvrdma_cmd_req *req,
> +		union pvrdma_cmd_resp *resp, unsigned resp_code)
> +{
> +	int err;
> +
> +	dev_dbg(&dev->pdev->dev, "post request to device\n");
> +
> +	/* Serializiation */
> +	down(&dev->cmd_sema);
> +
> +	BUILD_BUG_ON(sizeof(union pvrdma_cmd_req) !=
> +		     sizeof(struct pvrdma_cmd_modify_qp));
> +
> +	spin_lock(&dev->cmd_lock);
> +	memcpy(dev->cmd_slot, req, sizeof(*req));
> +	spin_unlock(&dev->cmd_lock);
> +
> +	init_completion(&dev->cmd_done);
> +	pvrdma_write_reg(dev, PVRDMA_REG_REQUEST, 0);
> +
> +	/* Make sure the request is written before reading status. */
> +	mb();
> +
> +	err = pvrdma_read_reg(dev, PVRDMA_REG_ERR);
> +	if (err == 0) {
> +		if (resp != NULL)
> +			err = pvrdma_cmd_recv(dev, resp, resp_code);
> +	} else {
> +		dev_warn(&dev->pdev->dev, "failed to write request %d\n", err);
> +	}

Please note that callers checks if err<0  while here err!=0 considered as
error.
Looking at similar code in pvrdma_pci_probe i can see that function
"translates" this error to -EINVAL. Suggesting to do the same here
(although -EINVAL is not a good choice, if device can be more friendly with
the return code then we can propagate it up or just print a suitable error
i.e. EAGAIN or ENOMEM otherwise EFAULT should be sufficient).

> +
> +	up(&dev->cmd_sema);
> +
> +	return err;
> +}
> -- 
> 2.7.4
> 
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