Re: [PATCH v8 00/14] Peripheral Image Loader support for Qualcomm SoCs running Linux host at EL2

[Bryan O'Donoghue <bryan.odonoghue@linaro.org>]

On 21/11/2025 11:01, Mukesh Ojha wrote:
> In May 2025, we discussed the challenges at Linaro Connect 2025 [1]
> related to Secure PAS remoteproc enablement when Linux is running at EL2
> for Qualcomm SoCs.
> 
> [1] https://resources.linaro.org/en/resource/sF8jXifdb9V1mUefdbfafa
> 
> Below, is the summary of the discussion.
> 
> Qualcomm is working to enable remote processors on the SA8775p SoC with
> a Linux host running at EL2. In doing so, it has encountered several
> challenges related to how the remoteproc framework is handled when Linux
> runs at EL1.
> 
> One of the main challenges arises from differences in how IOMMU
> translation is currently managed on SoCs running the Qualcomm EL2
> hypervisor (QHEE), where IOMMU translation for any device is entirely
> owned by the hypervisor. Additionally, the firmware for remote
> processors does not contain a resource table, which would typically
> include the necessary IOMMU configuration settings.
> 
> Qualcomm SoCs running with QHEE (EL2) have been utilizing the Peripheral
> Authentication Service (PAS) from TrustZone (TZ) firmware to securely
> authenticate and reset remote processors via a single SMC call,
> _auth_and_reset_. This call is first trapped by QHEE, which then invokes
> TZ for authentication. Once authentication is complete, the call returns
> to QHEE, which sets up the IOMMU translation scheme for the remote
> processors and subsequently brings them out of reset. The design of the
> Qualcomm EL2 hypervisor dictates that the Linux host OS running at EL1
> is not permitted to configure IOMMU translation for remote processors,
> and only a single-stage translation is configured.
> 
> To make the remote processor bring-up (PAS) sequence
> hypervisor-independent, the auth_and_reset SMC call is now handled
> entirely by TZ. However, the issue of IOMMU configuration remains
> unresolved, for example a scenario, when KVM host at EL2 has no
> knowledge of the remote processors’ IOMMU settings.  This is being
> addressed by overlaying the IOMMU properties when the SoC runs a Linux
> host at EL2. SMC call is being provided from the TrustZone firmware to
> retrieve the resource table for a given subsystem.
> 
> There are also remote processors such as those for video, camera, and
> graphics that do not use the remoteproc framework to manage their
> lifecycle. Instead, they rely on the Qualcomm PAS service to
> authenticate their firmware. These processors also need to be brought
> out of reset when Linux is running at EL2. The client drivers for these
> processors use the MDT loader function to load and authenticate
> firmware. Similar to the Qualcomm remoteproc PAS driver, they also need
> to retrieve the resource table, create a shared memory bridge
> (shmbridge), and map the resources before bringing the processors out of
> reset.
> 
> It is based on next-20251120 and tested on SA8775p which is now called
> Lemans IOT platform and does not addresses DMA problem discussed at
> [1] which is future scope of the series.
> 
> Changes in v8: https://lore.kernel.org/lkml/20251113-kvm-rproc-v7-v7-0-df4910b7c20a@oss.qualcomm.com/
>   - Addressed suggestion from Stephen which was regarding commit message(9/14),
>     debug log(12/14) suggestion, and return type change(4/14).
>   - Added R-b tag on 10/14 .
Sorry.

Did we actually come up with a cogent reason to omit the video firmware 
loading here ?

AFAIU it is required for Lemans and Glymur - leaving it out is blocking 
getting video stuff done and storing up trouble.

What exactly is the blockage - is it something you want help with ?

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bod