linux-kernel - Re: [PATCH v10 7/9] misc: bcm-vk: add Broadcom VK driver

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Message-ID: <202007071700.C567BA7B@keescook>
Date:   Tue, 7 Jul 2020 17:03:50 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Scott Branden <scott.branden@...adcom.com>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Wolfram Sang <wsa@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        David Brown <david.brown@...aro.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Shuah Khan <shuah@...nel.org>, bjorn.andersson@...aro.org,
        Shuah Khan <skhan@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        Olof Johansson <olof@...om.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Colin Ian King <colin.king@...onical.com>,
        Takashi Iwai <tiwai@...e.de>, linux-kselftest@...r.kernel.org,
        Andy Gross <agross@...nel.org>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Desmond Yan <desmond.yan@...adcom.com>,
        James Hu <james.hu@...adcom.com>
Subject: Re: [PATCH v10 7/9] misc: bcm-vk: add Broadcom VK driver

On Mon, Jul 06, 2020 at 04:23:07PM -0700, Scott Branden wrote:
> Add Broadcom VK driver offload engine.
> This driver interfaces to the VK PCIe offload engine to perform
> should offload functions as video transcoding on multiple streams
> in parallel.  VK device is booted from files loaded using
> request_firmware_into_buf mechanism.  After booted card status is updated
> and messages can then be sent to the card.
> Such messages contain scatter gather list of addresses
> to pull data from the host to perform operations on.
> 
> Signed-off-by: Scott Branden <scott.branden@...adcom.com>
> Signed-off-by: Desmond Yan <desmond.yan@...adcom.com>

nit: your S-o-b chain doesn't make sense (I would expect you at the end
since you're sending it and showing as the Author). Is it Co-developed-by?
https://www.kernel.org/doc/html/latest/process/submitting-patches.html#when-to-use-acked-by-cc-and-co-developed-by

> [...]
> +
> +		max_buf = SZ_4M;
> +		bufp = dma_alloc_coherent(dev,
> +					  max_buf,
> +					  &boot_dma_addr, GFP_KERNEL);
> +		if (!bufp) {
> +			dev_err(dev, "Error allocating 0x%zx\n", max_buf);
> +			ret = -ENOMEM;
> +			goto err_buf_out;
> +		}
> +
> +		bcm_vk_buf_notify(vk, bufp, boot_dma_addr, max_buf);
> +	} else {
> +		dev_err(dev, "Error invalid image type 0x%x\n", load_type);
> +		ret = -EINVAL;
> +		goto err_buf_out;
> +	}
> +
> +	ret = request_partial_firmware_into_buf(&fw, filename, dev,
> +						bufp, max_buf, 0);

Unless I don't understand what's happening here, this needs to be
reordered if you're going to keep Mimi happy and disallow the device
being able to see the firmware before it has been verified. (i.e. please
load the firmware before mapping DMA across the buffer.)

-- 
Kees Cook