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Date: Wed, 19 Jul 2023 23:57:51 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	virtualization@lists.linux-foundation.org,
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	John Fastabend <john.fastabend@gmail.com>, netdev@vger.kernel.org,
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Subject: Re: [PATCH vhost v11 05/10] virtio_ring: introduce
 virtqueue_dma_dev()
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	lindbergh.monkeyblade.net

On Thu, Jul 20, 2023 at 02:45:14PM +0800, Xuan Zhuo wrote:
>  virtqueue_dma_dev() return the device that working with the DMA APIs.
>  Then that can be used like other devices. So what is the problem.
> 
>  I always think the code path without the DMA APIs is the trouble for you.

Because we now have an API where the upper level drivers sometimes
see the dma device and sometimes not.  This will be abused and cause
trouble sooner than you can say "layering".