Re: [PATCH v4 00/12] Peripheral Image Loader support for Qualcomm SoCs running Linux host at EL2

[Mukesh Ojha]

On Tue, Oct 07, 2025 at 02:56:13PM -0700, Manivannan Sadhasivam wrote:
> 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?

It is not yet available in public, but I could share you internally.

> 
> - Mani
> 
> > Changes in v4: https://lore.kernel.org/lkml/20250921-kvm_rproc_pas-v3-0-458f09647920@xxxxxxxxxxxxxxxx/
> >  - 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@xxxxxxxxxxxxxxxx/
> >  - 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@xxxxxxxxxxx/
> >  - 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
> > 
> 
> -- 
> மணிவண்ணன் சதாசிவம்

-- 
-Mukesh Ojha