On 9/26/2023 6:02 PM, Sumit Garg wrote:
+cc OP-TEE ML
On Tue, 26 Sept 2023 at 13:47, Rijo Thomas Rijo-john.Thomas@amd.com wrote:
On 9/26/2023 1:19 PM, Sumit Garg wrote:
On Tue, 26 Sept 2023 at 12:53, Rijo Thomas Rijo-john.Thomas@amd.com wrote:
On 9/26/2023 12:14 PM, Sumit Garg wrote:
+cc Alex
On Tue, 26 Sept 2023 at 08:16, Jens Wiklander jens.wiklander@linaro.org wrote:
Hi,
[+cc Arnd]
On Tue, Sep 26, 2023 at 8:00 AM Sumit Garg sumit.garg@linaro.org wrote: > > +cc Jens > >> In a virtual environment, an application running in guest VM may want >> to delegate security sensitive tasks to a Trusted Application (TA) >> running within a Trusted Execution Environment (TEE). A TEE is a trusted >> OS running in some secure environment, for example, TrustZone on ARM >> CPUs, or a separate secure co-processor etc. > > I have been exploring this area quite recently with an effort to have a common VIRIO interface which can support different trusted OS implementations. I guess you intend to test it with AMD-TEE, right? Any plans to test it with OP-TEE? As currently we have these two supported upstream. >
Yes, we have tested with AMD-TEE. We have not yet tested with OP-TEE. Sure, we will try it out.
Glad to hear that. I can help get it tested with OP-TEE as well.
We will test it out internally. Shall let you know in case we need help.
> Do you currently have any virtio frontend/backend implementations for this? >
Yes, we have. Frontend is a Linux virtio-TEE driver, and backend is virtio-TEE device emulated in QEMU. We used the Xen hypervisor.
Can you share corresponding references? I can give it a try using Qemu with KVM.
We will share it in next couple of weeks. We have not yet hosted the code for external consumption.
>> >> A virtual TEE device emulates a TEE within a guest VM. Such a virtual >> TEE device supports multiple operations such as: >> >> VIRTIO_TEE_CMD_OPEN_DEVICE – Open a communication channel with virtio >> TEE device. >> VIRTIO_TEE_CMD_CLOSE_DEVICE – Close communication channel with virtio >> TEE device. >> VIRTIO_TEE_CMD_GET_VERSION – Get version of virtio TEE. >> VIRTIO_TEE_CMD_OPEN_SESSION – Open a session to communicate with >> trusted application running in TEE. >> VIRTIO_TEE_CMD_CLOSE_SESSION – Close a session to end communication >> with trusted application running in TEE. >> VIRTIO_TEE_CMD_INVOKE_FUNC – Invoke a command or function in trusted >> application running in TEE. >> VIRTIO_TEE_CMD_CANCEL_REQ – Cancel an ongoing command within TEE. >> > > How about shared memory support? We would like to register guest pages with the trusted OS.
We have a command VIRTIO_TEE_CMD_REGISTER_MEM for registering shared memory buffer with Trusted OS.
I suppose the commit message has to be appended then. Do you have the draft virtio-tee device specification ready for review? I would be interested to review that.
Yes, the command is missed out in the commit message.
With the commit message updated to include support for shared memory, feel free to add:
Acked-by: Sumit Garg sumit.garg@linaro.org
Okay. I have asked Jeshwanth to post a revised patch with updated commit message.
We are in the process of preparing virtio-tee device specification. We will be sending it out to this list.
I would also suggest you to CC: op-tee@lists.trustedfirmware.org for review.
Okay.
Thanks, Rijo
In this command, the guest pages are copied into a shadow buffer in the host OS. And this shadow buffer is mapped with Trusted OS. So, buffer-copy is involved.
One limitation, that we had was that the guest pages were non-contiguous. So, the number of physical pages that had to be mapped with Trusted OS was exceeding 64 entries when we were testing out the registering of guest pages. AMD-TEE Trusted OS can map a physically non-contiguous buffer, but the number of sg entries for such a buffer must be less than 64. So, we resorted to using a shadow buffer that is allocated within host, and gets mapped with Trusted OS.
I don't think OP-TEE OS has such a limitation on non-contiguous pages. So I would suggest you to keep VIRTIO_TEE_CMD_REGISTER_MEM as part of the ABI. It can be an optional feature for a particular trusted OS implementation to support.
Currently, the reg_mem (register memory) control is dictated by a flag in virtio-tee qemu code. This flag for our testing was hard-coded as false. We will enhance our code, so that it is configurable. The value of reg_mem shall be set to true/false depending upon whether the underlying TEE driver reports TEE_GEN_CAP_REG_MEM.
Sounds good to me.
-Sumit
Thanks, Rijo
-Sumit
Thanks, Rijo
Coincidently Arnd and I (among others) discussed this in person last week and the conclusion was that only temporary shared memory is possible with virtio. So the shared memory has to be set up and torn down by the host during each operation, typically open-session or invoke-func.
Agree as I was part of those discussions. But I would like to understand the reasoning behind it. Is there any restriction by VIRTIO specification that we can't register guest page PAs to a device (TEE in our case) to allow for zero copy transfers?
Alex mentioned some references to virtio GPU device. I suppose I need to dive into its implementation to see if there are any similarities to our use-case.
That might not be optimal if trying to maximize performance, but it is portable.
IMO, the ABI should be flexible enough to support a TEE with optimum performance.
-Sumit
Cheers, Jens
> > -Sumit > >> We would like to reserve device ID 46 for Virtio-TEE device. >> >> Signed-off-by: Jeshwanth Kumar jeshwanthkumar.nk@amd.com >> --- >> content.tex | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/content.tex b/content.tex >> index 0a62dce..644aa4a 100644 >> --- a/content.tex >> +++ b/content.tex >> @@ -739,6 +739,8 @@ \chapter{Device Types}\label{sec:Device Types} >> \hline >> 45 & SPI master \ >> \hline >> +46 & TEE device \ >> +\hline >> \end{tabular} >> >> Some of the devices above are unspecified by this document,