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

[NK, JESHWANTHKUMAR]

On 25-Oct-23 7:01 PM, Sumit Garg wrote:
> Hi Jeshwank,
>
> On Wed, 25 Oct 2023 at 12:27, jeshwank <JESHWANTHKUMAR.NK@xxxxxxx> wrote:
> > From: Jeshwanth Kumar N K <JESHWANTHKUMAR.NK@xxxxxxx>
> >
> > 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