Re: [PATCH v7 0/5] xen/arm: scmi: introduce SCI SCMI SMC multi-agent support

[Jan Beulich <jbeulich@xxxxxxxx>]

On 14.01.2026 19:29, Oleksii Moisieiev wrote:
> Inroducing patch series which includes implementation of the SCI SCMI
> SMC multi-agent support.
> This patch series follows RFC v5 [3] series which was introducing both
> SCMI single-agent and multi-agent support. After the discussion it was
> decided to split features and upstream singe-agent support first. This
> feature is merged for now to v4.21-rc2.
> I'm starting this patch series from v6 to save the discussion history
> and don't break changes log.
> 
> Patch - xen/domctl: extend XEN_DOMCTL_assign_device to handle not
> only iommu
> - add chainged handling of assigned DT devices to support
> access-controller functionality through SCI framework.
> Change was done in two parts:
>  - call to sci_do_domctl() to do_domctl()
>  - update iommu_do_dt_domctl() to check for dt_device_is_protected()
>  and not fail if DT device is not protected by IOMMU
> 
> Patch - xen/arm: scmi: introduce SCI SCMI SMC multi-agent driver
> - add Xen-specific SCMI container compatible `xen,sci`
>   under `/chosen/xen`; Xen binds only to the `arm,scmi-smc` inside it and
>   ignores other SCMI nodes (e.g. under `/firmware`).
> - add `scmi-secondary-agents` and `#scmi-secondary-agents-cells` to describe
>   func_id/shmem/(optional agent_id) tuples for secondary agents.
> - each guest using SCMI supplies its agent_id (dom0 via `dom0=sci-agent-id=`,
>   toolstack via `arm_sci = "type=scmi_smc_multiagent,agent_id=..."`, dom0less
>   via `xen,sci_type` + `xen,sci-agent-id` in `xen,domain`).
> - factor out SCMI generic definitions and shmem code.
> - passthrough configuration for SCMI guests mirrors other HW passthrough.
> 
> Patch - docs: arm: add SCI SCMI SMC multi-agent driver docs
> - document the Xen SCMI container under `/chosen/xen/xen_scmi_config` and the
>   mediator’s binding rules; update examples accordingly.
> 
> All Xen-specific SCMI configuration now lives under `/chosen/g`
> to keep host DT changes isolated while leaving the host `/firmware/scmi`
> untouched for Dom0 consumption.
> 
> Code can be found at:
> https://github.com/oleksiimoisieiev/xen/tree/scmi_ma_upstrv6
> 
> [1] RFC v2:
> http://patchwork.kernel.org/project/xen-devel/cover/cover.1644341635.git.oleksii_moisieiev@xxxxxxxx/
> [2] RFC v3:
> https://patchwork.kernel.org/project/xen-devel/patch/20250311111618.1850927-1-grygorii_strashko@xxxxxxxx
> [3] RFC v5:
> https://lore.kernel.org/xen-devel/cover.1753184487.git.oleksii_moisieiev@xxxxxxxx/
> [4] SCMI single-agent:
> https://lore.kernel.org/xen-devel/cover.1756995595.git.oleksii_moisieiev@xxxxxxxx/
> SCMI spec:
> https://developer.arm.com/documentation/den0056/e/?lang=en
> 
> SCMI bindings:
> https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
> https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/access-controllers/access-controllers.yaml
> 
> Reference EL3 FW:
> RPI5: https://github.com/xen-troops/arm-trusted-firmware/commits/rpi5_dev/
> Renesas v4h:
> https://github.com/GrygiriiS/arm-trusted-firmware/commits/rcar_gen4_v2.7_v4x-scmi_upd/
> 
> base-commit: dbe60f244c (Update Xen to 4.21, 2025-02-21)
> 
> Changes in v7:
> - update domctl to build on both Arm and x86 platforms
> - move ret1 declaration to the top of the function as required by code
> style
> - x86 guidance: removed the speculative note; header now just says
>   each arch supplies its own implementation or macro.
> - name spacing: dropped the double-underscore; the helpers are now
>   memcpy_fromio / memcpy_toio. The header also explicitly allows an
>   arch to define these as macros before including it.
> - updated io.c to keep 32-bit transfers safe on arm32
> - moved to __raw_read*/__raw_write* accessors to avoid endianness conversion.
> - split the helpers into separate compilation units
> - rework scmi nodes for xen to match on compatible string instead of
> the direct path
> - update documentation in section of the xen_scmi configuration which
> is matched by "xen,sci" compatible instead of the direct path.
> 
> Changes in v6:
> - change iommu_do_domctl and sci_do_domctl command order and
> call sci_do_domctl first which will produce cleaner code path.
> Also dropped changing return code when iommu was disabled in
> iommu_do_domctl.
> - sorted objs in Makefile alhabetically
> - added newline at the end of Makefile
> - used uint{N}_t intead of u{N}
> - add comment about why 32 bit IO operations were used
> - updated cast opertaions to avoid dropping constness which is wrong
> - move function definitions to generic place so the could be reused by
> other arch
> - add SPDX tag to io.c
> - updated scmi-shmem to use io.h from generic location
> - update scmi_agent_id parameter to be provided inside dom0= parameter
> list and have the following format "dom0=sci-agent-id=0"
> This change was done as a response for Stefano comment and
> requires a lot of code changes, but produces much cleaner solution
> that's why I've added it to the code.
> - fix file comments and return codes
> - fix lenght checks in shmem_{get,put}_message to use offsetof
> - remove len member from scmi_channel structure as it is not used
> - set scmi-secondary-agents property to be mandatory since if no
> secondary agents were provided then there is no sence to enable scmi
> when no secondary agents are populated to the Domains
> - update documentation in booting.txt, added xen_scmi node to the
> example
> - adjust d->arch.sci_enabled value in scmi_domain_destroy
> - fix lock management in smc_create_channel call
> - avoid extra map_channel_memory command for Xen management channel
> because collect_agent_id call unmaps memory if DOMID_XEN is not
> set. So for Xen management channel we can init domain_id ad DOMID_XEN
> before calling collect_agent_id so memory shouldn't be unmapped.
> - remove all HVC mentions from the multi-agent doc
> - update sci-agent-id parameter description in the documentation
> - add missing Sign-of
> - minor fixes across the document
> 
> Changes in v5:
> - return -EINVAL if mediator without assign_dt_device was provided
> - invert return code check for iommu_do_domctl in
> XEN_DOMCTL_assign_device domctl processing to make cleaner code
> - change -ENOTSUPP error code to -ENXIO in sci_do_domctl
> - handle -ENXIO return comde of iommu_do_domctl
> - leave !dt_device_is_protected check in iommu_do_dt_domctl to make
> code work the same way it's done in "handle_device" call while
> creating hwdom(dom0) and "handle_passthrough_prop" call for dom0less
> creation
> - drop return check from sci_assign_dt_device call as not needed
> - do not return EINVAL when addign_dt_device is not set. That is
> because this callback is optional and not implemented in single-agent driver
> - move memcpy_toio/fromio to the generic place
> - fix device-tree example format in booting.txt, added ";" after "}".
> - update define in scmi-proto.h
> - update define in scmi-shmem.h file
> - scmi_assign_device - do not ignore -EOPNOTSUPP return
> code of the do_smc_xfer
> - remove overwriting agent_channel->agent_id after
> SCMI_BASE_DISCOVER_AGENT call
> - add multi-agent files to the MAINTAINERS
> - add SCMI multi-agent description to the SUPPORT.md
> - handle ARM_SMCCC_INVALID_PARAMETER return code and return -EINVAL
> for smc call
> - updated collect_agents function. Set agent_id parameter as optional
> in scmi-secondary-agents device-tree property
> - introduce "#scmi-secondary-agents-cells" parameter to set if
> agent_id was provided
> - reanme xen,scmi-secondary-agents property to scmi-secondary-agents
> - move memcpu_toio/fromio for the generic place
> - update Xen to get management channel from /chosen/xen,config node
> - get hypervisor channnel from node instead of using hardcoded
> - update handling scmi and shmem nodes for the domain
> - Set multi-agent driver to support only Arm64
> - rework multi-agent driver to leave Host Device-tree unmodified
> 
> Changes in v4:
> - toolstack comments from Anthony PERARD
> - added dom0less support
> - added doc for "xen,scmi-secondary-agents"
> 
> Grygorii Strashko (2):
>   xen/domctl: extend XEN_DOMCTL_assign_device to handle not only iommu
>   docs: arm: add SCI SCMI SMC multi-agent driver docs
> 
> Oleksii Moisieiev (3):
>   xen: arm: smccc: add INVALID_PARAMETER error code
>   lib/arm: Add I/O memory copy helpers
>   xen/arm: scmi: introduce SCI SCMI SMC multi-agent driver
> 
>  MAINTAINERS                                   |   4 +
>  SUPPORT.md                                    |  11 +
>  .../arm/firmware/arm-scmi.rst                 | 341 ++++++++
>  docs/man/xl.cfg.5.pod.in                      |  13 +
>  docs/misc/arm/device-tree/booting.txt         | 122 +++
>  docs/misc/xen-command-line.pandoc             |  19 +-
>  tools/libs/light/libxl_arm.c                  |   4 +
>  tools/libs/light/libxl_types.idl              |   4 +-
>  tools/xl/xl_parse.c                           |  12 +
>  xen/arch/arm/dom0less-build.c                 |  11 +
>  xen/arch/arm/domain_build.c                   |  26 +-
>  xen/arch/arm/firmware/Kconfig                 |  12 +
>  xen/arch/arm/firmware/Makefile                |   1 +
>  xen/arch/arm/firmware/sci.c                   |  35 +
>  xen/arch/arm/firmware/scmi-proto.h            | 164 ++++
>  xen/arch/arm/firmware/scmi-shmem.c            | 115 +++
>  xen/arch/arm/firmware/scmi-shmem.h            |  45 +
>  xen/arch/arm/firmware/scmi-smc-multiagent.c   | 815 ++++++++++++++++++
>  xen/arch/arm/include/asm/firmware/sci.h       |  14 +
>  xen/arch/arm/include/asm/smccc.h              |   1 +
>  xen/common/domctl.c                           |  35 +-
>  xen/drivers/passthrough/device_tree.c         |   6 +
>  xen/include/public/arch-arm.h                 |   3 +
>  xen/include/xen/lib/io.h                      |  65 ++
>  xen/lib/Makefile                              |   1 +
>  xen/lib/arm/Makefile                          |   1 +
>  xen/lib/arm/memcpy_fromio.c                   |  48 ++
>  xen/lib/arm/memcpy_toio.c                     |  48 ++
>  28 files changed, 1972 insertions(+), 4 deletions(-)
>  create mode 100644 xen/arch/arm/firmware/scmi-proto.h
>  create mode 100644 xen/arch/arm/firmware/scmi-shmem.c
>  create mode 100644 xen/arch/arm/firmware/scmi-shmem.h
>  create mode 100644 xen/arch/arm/firmware/scmi-smc-multiagent.c

Just like done here, can ...

>  create mode 100644 xen/include/xen/lib/io.h
>  create mode 100644 xen/lib/arm/Makefile
>  create mode 100644 xen/lib/arm/memcpy_fromio.c
>  create mode 100644 xen/lib/arm/memcpy_toio.c

... new files please use dashes in favor of underscores?

Jan