Message-ID: <b6akgk6nymtaxqak2procz4gkq6hrj2ao2yaw3axo6yjn7ekuk@g66xx5vd3fcp>
Date: Tue, 7 Oct 2025 14:56:13 -0700
From: Manivannan Sadhasivam <mani@...nel.org>
To: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>, 
	Mathieu Poirier <mathieu.poirier@...aro.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org, linux-remoteproc@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Subject: Re: [PATCH v4 00/12] Peripheral Image Loader support for Qualcomm
 SoCs running Linux host at EL2

On Tue, Oct 07, 2025 at 10:18:45PM +0530, Mukesh Ojha wrote:
> A few months ago, we discussed the challenges at Linaro Connect 2025 [1] 
> related to Secure PAS remoteproc enablement when Linux is running at EL2.
> 
> [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-20251007 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.
> 

Could you please add a link to the modified TZ firmware for Lemans, required to
make use this patchset?

- Mani

> Changes in v4: https://lore.kernel.org/lkml/20250921-kvm_rproc_pas-v3-0-458f09647920@oss.qualcomm.com/
>  - Fixed kernel robot warning/errors.
>  - Reworded some of the commit log, code comment as per suggestion from Bryan.
>  - Added support of gpdsp0 and gpdsp1 and disabled iris node.
>  - Add R-b tag to some of the reviewed patches.
>  - Rename struct qcom_scm_pas_cxt to qcom_scm_pas_context.
> 
> Changes in v3: https://lore.kernel.org/lkml/20250819165447.4149674-1-mukesh.ojha@oss.qualcomm.com/
>  - Dropped video subsystem enablement for now, could add it in future
>    or on a separate series.
>  - Addressed most of the suggestion from Stephen and Bryan like some
>    remoteproc code checking resource table presence or right error
>    code propagation above the layer.
>  - Added leman-el2 overlay file.
>  - Added missed iommus binding which was missed last series.
>  - Separated qcom_mdt_pas_load() patch and its usage.
>  - Patch numbering got changed compared to last version
> 
> Changes in v2: https://lore.kernel.org/lkml/20241004212359.2263502-1-quic_mojha@quicinc.com/
>  - A lot has changed from the V1 and a fresh look would be preferred.
>  - Removed approach where device tree contain devmem resources in
>    remoteproc node.
>  - SHMbridge need to created for both carveout and metadata memory
>    shared to TZ in a new way.
>  - Now, resource table would be given by SMC call which need to mapped
>    along with carveout before triggering _auth_and_reset_.
>  - IOMMU properties need to be added to firmware devices tree node when Linux
>    control IOMMU.
> 
> ---
> Mukesh Ojha (12):
>       dt-bindings: remoteproc: qcom,pas: Add iommus property
>       firmware: qcom_scm: Rename peripheral as pas_id
>       firmware: qcom_scm: Introduce PAS context initialization and destroy helper
>       soc: qcom: mdtloader: Add PAS context aware qcom_mdt_pas_load() function
>       remoteproc: pas: Replace metadata context with PAS context structure
>       firmware: qcom_scm: Add a prep version of auth_and_reset function
>       firmware: qcom_scm: Simplify qcom_scm_pas_init_image()
>       firmware: qcom_scm: Add SHM bridge handling for PAS when running without QHEE
>       firmware: qcom_scm: Add qcom_scm_pas_get_rsc_table() to get resource table
>       remoteproc: pas: Extend parse_fw callback to fetch resources via SMC call
>       remoteproc: qcom: pas: Enable Secure PAS support with IOMMU managed by Linux
>       arm64: dts: qcom: Add EL2 overlay for Lemans
> 
>  .../bindings/remoteproc/qcom,pas-common.yaml       |   3 +
>  arch/arm64/boot/dts/qcom/Makefile                  |   7 +-
>  arch/arm64/boot/dts/qcom/lemans-el2.dtso           |  41 ++
>  drivers/firmware/qcom/qcom_scm.c                   | 415 ++++++++++++++++++---
>  drivers/firmware/qcom/qcom_scm.h                   |   1 +
>  drivers/remoteproc/qcom_q6v5_pas.c                 | 187 ++++++++--
>  drivers/soc/qcom/mdt_loader.c                      |  32 +-
>  include/linux/firmware/qcom/qcom_scm.h             |  36 +-
>  include/linux/soc/qcom/mdt_loader.h                |  16 +-
>  9 files changed, 635 insertions(+), 103 deletions(-)
> ---
> base-commit: 68842969e138d9ad3e3aa2bbd65d514df1581b5c
> change-id: 20251007-kvm_rprocv4_next-20251007-5e4ea5a978da
> 
> Best regards,
> -- 
> -Mukesh Ojha
> 

-- 
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