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Date:   Mon, 30 Oct 2023 06:33:05 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     "NK, JESHWANTHKUMAR" <jeshwanthkumar.nk@amd.com>
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Subject: Re: [PATCH 1/3] crypto: ccp - Add function to allocate and free
 memory using DMA APIs
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On Fri, Oct 27, 2023 at 07:05:17PM +0530, NK, JESHWANTHKUMAR wrote:
> Can you please elaborate a bit more?

Becasue the DMA API is a blackbox.  You can pass the dma_addr_t to
hardware, and you can use the kernel virtual address.  That it can
sometimes be implemented using the IMMU API is an implementation
detail.  Similarly you can only feeds iovas generated by the IOMMU
API into the IOMMU API, not any random other scalar value, which
is what you can get from the DMA API.