On Tue, Nov 04, 2025 at 04:25:26PM +0000, Bryan O'Donoghue wrote: > On 04/11/2025 07:35, 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-20251103 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 v6: > > https://lore.kernel.org/lkml/[email protected]/ > > - Added comments made by Bryan to save some cycles and added in 2/14 > > which could change patch order. > > - Renamed qcom_scm_pas_context_init to devm_qcom_scm_pas_context_init() > > - Replaced devm_kzalloc with kzalloc for output_rt in scm function as > > remoteproc framework does not usage devm_ api for resource table > > pointer which is cause mem-abort issue start/stop test. > > - Removed union usage and redundant code from > > qcom_scm_pas_prep_and_init_image(). > > > > Changes in v5: > > https://lore.kernel.org/lkml/20251007-kvm_rprocv4_next-20251007-v4-0-de841623a...@oss.qualcomm.com/ > > - Replaced minitems with maxitems. > > - Addressed comments made by Bryan, Mani and Konrad. > > - Fixed some of highlighted issues in v4. > > - Added a new patch which removes qcom_mdt_pas_init() from exported > > symbol list. > > - Slight change in v4's 5/12, so that it does use qcom_mdt_pas_load() > > directly while it should use in the commit where it gets introduced. > > Hence, reordered the patches a bit like v4 5/12 comes early before > > 4/12. > > > > Changes in v4: > > https://lore.kernel.org/lkml/[email protected]/ > > - 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/[email protected]/ > > - Dropped video subsystem enablement for now, could add it in future > > or on a separate series. > > I specifically think it is the wrong thing to do, to drop video enablement > from this series.
There is no dependency of this series on video enablement. The only reason I included it in my initial series was that video or other non-remoteproc subsystems would need to call the resource table SMC call and map the resources. Since I have dropped video support have dropped the the helper function too that parses and maps the resources in this newer series, it is no longer required. https://lore.kernel.org/lkml/[email protected]/ > > Its just papering over the cracks. The right thing to do is to have the > technical disucssion and agree a way forward, not to drop things that feel > too contentious. > > What's really so contentious about > > video-firmware { > iommu data here > }; > > As has been done with ChromeOS on venus thus far ? > > All that has to be made is a case for it. Since there was an objection to removing the Venus YAML from the Iris YAML [1], we cannot use it. We had a few similar use cases as mentioned here [2], and you were part of all the discussions and agreed to remove the item that could take time [3]. Therefore, it seemed valid to drop it for now. A new approach[4] for video to handle these kind of sceanario has been posted. [1] https://lore.kernel.org/lkml/[email protected]/ [2] https://lore.kernel.org/all/[email protected]/T/#m9891945187671417f25f134097383b72aa7f47c2 [3] https://lore.kernel.org/lkml/[email protected]/ [4] https://lore.kernel.org/lkml/[email protected]/ > > > - 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/[email protected]/ > > - 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 (14): > > dt-bindings: remoteproc: qcom,pas: Add iommus property > > firmware: qcom_scm: Remove redundant piece of code > > firmware: qcom_scm: Rename peripheral as pas_id > > firmware: qcom_scm: Introduce PAS context initialization helper > > function > > remoteproc: pas: Replace metadata context with PAS context structure > > soc: qcom: mdtloader: Add PAS context aware qcom_mdt_pas_load() > > function > > soc: qcom: mdtloader: Remove qcom_mdt_pas_init() from exported > > symbols > > 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 | 10 + > > arch/arm64/boot/dts/qcom/lemans-el2.dtso | 41 +++ > > drivers/firmware/qcom/qcom_scm.c | 387 > > ++++++++++++++++++--- > > drivers/firmware/qcom/qcom_scm.h | 1 + > > drivers/remoteproc/qcom_q6v5_pas.c | 166 +++++++-- > > drivers/soc/qcom/mdt_loader.c | 43 ++- > > include/linux/firmware/qcom/qcom_scm.h | 30 +- > > include/linux/soc/qcom/mdt_loader.h | 22 +- > > 9 files changed, 593 insertions(+), 110 deletions(-) > > --- > > base-commit: 9823120909776bbca58a3c55ef1f27d49283c1f3 > > change-id: 20251104-kvm_rproc_v6-6329e4d594fe > > > > Best regards, > > -- > > -Mukesh Ojha > > > > > -- -Mukesh Ojha
