Re: [PATCH v6 0/7] Add mediate-drm secure flow for SVP - Linaro-mm-sig

30 May 2024

      On Tue, May 28, 2024 at 07:15:34AM GMT, Jason-JH Lin (林睿祥) wrote:
...
Hi Maxime,
On Mon, 2024-05-27 at 16:06 +0200, Maxime Ripard wrote:
...
Hi,
On Sun, May 26, 2024 at 07:29:21AM GMT, Jason-JH.Lin wrote:
...
From: Jason-jh Lin jason-jh.lin@mediatek.corp-partner.google.com
Memory Definitions:
secure memory - Memory allocated in the TEE (Trusted Execution
Environment) which is inaccessible in the REE (Rich Execution
Environment, i.e. linux kernel/userspace).
secure handle - Integer value which acts as reference to 'secure
memory'. Used in communication between TEE and REE to reference
'secure memory'.
secure buffer - 'secure memory' that is used to store decrypted,
compressed video or for other general purposes in the TEE.
secure surface - 'secure memory' that is used to store graphic
buffers.
Memory Usage in SVP:
The overall flow of SVP starts with encrypted video coming in from
an
outside source into the REE. The REE will then allocate a 'secure
buffer' and send the corresponding 'secure handle' along with the
encrypted, compressed video data to the TEE. The TEE will then
decrypt
the video and store the result in the 'secure buffer'. The REE will
then allocate a 'secure surface'. The REE will pass the 'secure
handles' for both the 'secure buffer' and 'secure surface' into the
TEE for video decoding. The video decoder HW will then decode the
contents of the 'secure buffer' and place the result in the 'secure
surface'. The REE will then attach the 'secure surface' to the
overlay
plane for rendering of the video.
Everything relating to ensuring security of the actual contents of
the
'secure buffer' and 'secure surface' is out of scope for the REE
and
is the responsibility of the TEE.
DRM driver handles allocation of gem objects that are backed by a
'secure
surface' and for displaying a 'secure surface' on the overlay
plane.
This introduces a new flag for object creation called
DRM_MTK_GEM_CREATE_RESTRICTED which indicates it should be a
'secure
surface'. All changes here are in MediaTek specific code.

TODO:

Drop MTK_DRM_IOCTL_GEM_CREATE and use DMA_HEAP_IOCTL_ALLOC in

userspace
2) DRM driver use secure mailbox channel to handle normal and
secure flow
3) Implement setting mmsys routing table in the secure world series
I'm not sure what you mean here. Why are you trying to upstream
something that still needs to be removed from your patch series?
Because their is too much patches need to be fixed in this series, so I
list down the remaining TODO items and send to review for the other
patches.
Sorry for the bothering, I'll drop this at the next version.
If you don't intend to use it, we just shouldn't add it. Removing the
TODO item doesn't make sense, even more so if heaps should be the way
you handle this.
...
...
Also, I made some comments on the previous version that have been
entirely ignored and still apply on this version:
https://lore.kernel.org/dri-devel/20240415-guppy-of-perpetual-current-3a7974...
...
I lost that mail in my mailbox, so I didn't reply at that time.
I have imported that mail and replied to you. Hope you don't mind :)
I haven't received that answer
Maxime