linux-kernel - Re: [PATCH 0/3] Introduce DMA APIs to allocate and free TEE shared memory

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Message-ID: <4a261870-03e0-49f8-b968-4cbcf646d9eb@amd.com>
Date:   Thu, 26 Oct 2023 16:00:08 +0530
From:   "NK, JESHWANTHKUMAR" <jeshwanthkumar.nk@....com>
To:     Sumit Garg <sumit.garg@...aro.org>
Cc:     thomas.lendacky@....com, john.allen@....com,
        herbert@...dor.apana.org.au, davem@...emloft.net,
        jens.wiklander@...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 0/3] Introduce DMA APIs to allocate and free TEE shared
 memory


On 25-Oct-23 7:01 PM, Sumit Garg wrote:
> Hi Jeshwank,
>
> On Wed, 25 Oct 2023 at 12:27, jeshwank <JESHWANTHKUMAR.NK@....com> wrote:
>> From: Jeshwanth Kumar N K <JESHWANTHKUMAR.NK@....com>
>>
>> At present, the shared memory for TEE ring buffer, command buffer and
>> data buffer is allocated using get_free_pages(). The driver shares the
>> physical address of these buffers with PSP so that it can be mapped by
>> the Trusted OS.
>>
>> In this patch series we have replaced get_free_pages() with
>> dma_alloc_coherent() to allocate shared memory to cleanup the existing
>> allocation method.
> Thanks for putting this together but I can't find the reasoning behind
> this change neither in this commit message and nor in the patch
> descriptions. Care to explain why?
>
> -Sumit
Hi Sumit,

We see that there is an advantage in using dma_alloc_coherent() over 
get_free_pages(). The dma-ops associated with PSP PCIe device can be 
overridden. This capability will be helpful when we enable 
virtualization support. We plan to post a virtualization related patch 
in future.

Regards,

Jeshwanth

>
>> Rijo Thomas (3):
>>    crypto: ccp - Add function to allocate and free memory using DMA APIs
>>    crypto: ccp - Use psp_tee_alloc_buffer() and psp_tee_free_buffer()
>>    tee: amdtee: Use psp_tee_alloc_buffer() and psp_tee_free_buffer()
>>
>>   drivers/crypto/ccp/psp-dev.c        |   3 +
>>   drivers/crypto/ccp/tee-dev.c        | 119 ++++++++++++++++++----------
>>   drivers/crypto/ccp/tee-dev.h        |  11 +--
>>   drivers/tee/amdtee/amdtee_private.h |  18 ++---
>>   drivers/tee/amdtee/call.c           |  74 ++++++++---------
>>   drivers/tee/amdtee/core.c           |  72 ++++++++++-------
>>   drivers/tee/amdtee/shm_pool.c       |  21 ++---
>>   include/linux/psp-tee.h             |  47 +++++++++++
>>   8 files changed, 221 insertions(+), 144 deletions(-)
>>
>> --
>> 2.25.1
>>