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Date:   Thu, 21 Jan 2021 10:45:49 +0100
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Zhou Wang <wangzhou1@hisilicon.com>
Cc:     Zhangfei Gao <zhangfei.gao@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>,
        linux-accelerators@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        Sihang Chen <chensihang1@hisilicon.com>
Subject: Re: [PATCH] uacce: Add uacce_ctrl misc device
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On Thu, Jan 21, 2021 at 05:09:14PM +0800, Zhou Wang wrote:
> When IO page fault happens, DMA performance will be affected. Pin user page
> can avoid IO page fault, this patch introduces a new char device named
> /dev/uacce_ctrl to help to maintain pin/unpin pages. User space can do
> pin/unpin pages by ioctls of an open file of /dev/uacce_ctrl, all pinned
> pages under one file will be unpinned in file release process.

Also, what are you really trying to do here?  If you need to mess with
memory pages, why can't the existing memory apis work properly for you?
Please work with the linux-mm developers to resolve the issue using the
standard apis and not creating a one-off char device node for this type
of thing.

thanks,

greg k-h