linux-kernel - Re: [PATCH 1/3] crypto: ccp - Add function to allocate and free memory using DMA APIs

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Date:   Wed, 1 Nov 2023 19:42:16 +0530
From:   "NK, JESHWANTHKUMAR" <jeshwanthkumar.nk@....com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     thomas.lendacky@....com, john.allen@....com,
        herbert@...dor.apana.org.au, davem@...emloft.net,
        jens.wiklander@...aro.org, sumit.garg@...aro.org,
        jarkko.nikula@...ux.intel.com, mario.limonciello@....com,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        op-tee@...ts.trustedfirmware.org,
        Mythri.Pandeshwarakrishna@....com, Devaraj.Rangasamy@....com,
        Rijo-john.Thomas@....com, nimesh.easow@....com
Subject: Re: [PATCH 1/3] crypto: ccp - Add function to allocate and free
 memory using DMA APIs

Hi Christoph,

On 30-Oct-23 7:03 PM, Christoph Hellwig wrote:
> 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.

Thanks for the explanation, I will send a new version of the patch.

Regards,

Jeshwanth