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Message-ID: <f21143fb-91d2-4186-938e-0d147e32aa76@amd.com>
Date: Mon, 30 Oct 2023 11:51:06 +0530
From: "NK, JESHWANTHKUMAR" <jeshwanthkumar.nk@....com>
To: Tom Lendacky <thomas.lendacky@....com>,
Sumit Garg <sumit.garg@...aro.org>
Cc: 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, ray.huang@....com,
stefano.stabellini@....com
Subject: Re: [PATCH 0/3] Introduce DMA APIs to allocate and free TEE shared
memory
Hi Tom,
On 26-Oct-23 8:23 PM, Tom Lendacky wrote:
> On 10/26/23 05:30, NK, JESHWANTHKUMAR wrote:
>>
>> 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.
>
> To be specific, you are referring to Xen virtualization support,
> correct? Because I don't see how this works in a Qemu/KVM environment
> where you would get a GPA and not an SPA.
The patch is not specific to Xen. We have verified it in Qemu/KVM and
Xen PV mode. Support for Xen PVH mode will be added as a separate patch.
>
> If that is the case, you should clearly specify that. Also, this looks
> like it should be introduced with the virtualization support that you
> submit in the future and not before.
I will update the commit message in the next version of the patch series
to include these details.
> Thanks,
> Tom
>
>>
>> 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
>>>>
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