[RFC PATCH v3 0/6] virt: bao: Add Bao hypervisor IPC and I/O dispatcher drivers

[João Peixoto]

This series adds guest-side drivers for the Bao static-partitioning
hypervisor: an IPC shared-memory driver and an I/O dispatcher, plus their
device-tree bindings, UAPI and MAINTAINERS entry.

Bao is a lightweight static-partitioning hypervisor for embedded and
safety-critical systems.
- The IPC shared-memory driver lets Bao guests exchange data through a
  shared-memory region split into a read and a write channel.
- The I/O dispatcher lets a backend guest service paravirtualised (VirtIO)
  I/O on behalf of frontend guests.

Sent as RFC: the RISC-V backend uses the SBI experimental extension space
(see "Open items" below), and the device-tree bindings were reworked in this
version and would benefit from another look.

## Changes since v2
- dt-bindings (ipcshmem): describe the two channels through reg/reg-names,
  drop read-channel/write-channel and the "id" property, use a vendor
  "bao,id", and use a generic node name (Krzysztof Kozlowski).
- dt-bindings (io-dispatcher): one node per backend device (single reg +
  interrupt) instead of one node describing many devices, modelled on the
  gunyah/Mediatek Genio bindings (Krzysztof Kozlowski).
- io dispatcher driver: one platform device per device model (/dev/bao-dmX);
  removed the global DM list, the anonymous-inode fd and the dispatcher
  indirection ioctl; fixed a leak and probe error-path bugs; initialise
  virtio_requests_lock and the hypercall context fields.
- ipcshmem driver: derive the two regions from reg; drop the success print;
  do the range arithmetic in u64.
- Kconfig: fix the help-text indentation (Randy Dunlap).
- style: unwrap the few-char line wraps; the IPC hypercall helper now takes a
  single argument and fits on one line (Andrew Jones).
- riscv: use BAO_SBI_EXT_ID consistently, document that it is in the SBI
  experimental extension space, and drop the redundant ecall input
  constraints (Andrew Jones).
- commit messages: rewritten to kernel style; the "consolidate the IPC
  hypercall ID" patch now explains why and covers the signature change
  (Greg KH).
- process: sent as a fresh thread with this changelog, and the mail setup that
  bounced v1/v2 is fixed (Krzysztof Kozlowski, Greg KH).

## Open items / still under discussion
- RISC-V uses the experimental SBI extension ID (0x08000ba0). A permanent
  implementation ID must be registered in the RISC-V SBI spec before RISC-V
  can be non-experimental; hence RFC.
- Whether the Remote I/O hypercall must follow SBI chapter-3 register rules
  (Andrew Jones) — see the reply on patch 4.
- The "bao,id" property and the "bao" vendor prefix (Krzysztof Kozlowski) —
  rationale is in the bindings; alternatives welcome.

Link to v2: https://lore.kernel.org/all/20260107162829.416885-1-joaopeixoto@osyx.tech/

João Peixoto (6):
  dt-bindings: bao: add IPC shared-memory device
  virt: bao: add IPC shared-memory driver
  dt-bindings: bao: add I/O dispatcher device
  virt: bao: add I/O dispatcher driver
  virt: bao: consolidate the IPC hypercall ID in include/linux/bao.h
  MAINTAINERS: add Bao hypervisor entry

 .../bindings/bao/bao,io-dispatcher.yaml       |  58 +++
 .../devicetree/bindings/bao/bao,ipcshmem.yaml |  59 +++
 .../devicetree/bindings/vendor-prefixes.yaml  |   2 +
 .../userspace-api/ioctl/ioctl-number.rst      |   2 +
 MAINTAINERS                                   |  13 +
 arch/arm/include/asm/bao.h                    |  60 +++
 arch/arm64/include/asm/bao.h                  |  60 +++
 arch/riscv/include/asm/bao.h                  |  66 +++
 drivers/virt/Kconfig                          |   2 +
 drivers/virt/Makefile                         |   2 +
 drivers/virt/bao/Kconfig                      |   5 +
 drivers/virt/bao/Makefile                     |   4 +
 drivers/virt/bao/io-dispatcher/Kconfig        |  16 +
 drivers/virt/bao/io-dispatcher/Makefile       |   4 +
 drivers/virt/bao/io-dispatcher/bao_drv.h      | 349 +++++++++++++++
 drivers/virt/bao/io-dispatcher/dm.c           | 316 ++++++++++++++
 drivers/virt/bao/io-dispatcher/driver.c       |  95 +++++
 drivers/virt/bao/io-dispatcher/intc.c         |  64 +++
 drivers/virt/bao/io-dispatcher/io_client.c    | 401 ++++++++++++++++++
 .../virt/bao/io-dispatcher/io_dispatcher.c    | 181 ++++++++
 drivers/virt/bao/io-dispatcher/ioeventfd.c    | 323 ++++++++++++++
 drivers/virt/bao/io-dispatcher/irqfd.c        | 314 ++++++++++++++
 drivers/virt/bao/ipcshmem/Kconfig             |  10 +
 drivers/virt/bao/ipcshmem/Makefile            |   3 +
 drivers/virt/bao/ipcshmem/ipcshmem.c          | 228 ++++++++++
 include/linux/bao.h                           |  44 ++
 include/uapi/linux/bao.h                      |  96 +++++
 27 files changed, 2777 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/bao/bao,io-dispatcher.yaml
 create mode 100644 Documentation/devicetree/bindings/bao/bao,ipcshmem.yaml
 create mode 100644 arch/arm/include/asm/bao.h
 create mode 100644 arch/arm64/include/asm/bao.h
 create mode 100644 arch/riscv/include/asm/bao.h
 create mode 100644 drivers/virt/bao/Kconfig
 create mode 100644 drivers/virt/bao/Makefile
 create mode 100644 drivers/virt/bao/io-dispatcher/Kconfig
 create mode 100644 drivers/virt/bao/io-dispatcher/Makefile
 create mode 100644 drivers/virt/bao/io-dispatcher/bao_drv.h
 create mode 100644 drivers/virt/bao/io-dispatcher/dm.c
 create mode 100644 drivers/virt/bao/io-dispatcher/driver.c
 create mode 100644 drivers/virt/bao/io-dispatcher/intc.c
 create mode 100644 drivers/virt/bao/io-dispatcher/io_client.c
 create mode 100644 drivers/virt/bao/io-dispatcher/io_dispatcher.c
 create mode 100644 drivers/virt/bao/io-dispatcher/ioeventfd.c
 create mode 100644 drivers/virt/bao/io-dispatcher/irqfd.c
 create mode 100644 drivers/virt/bao/ipcshmem/Kconfig
 create mode 100644 drivers/virt/bao/ipcshmem/Makefile
 create mode 100644 drivers/virt/bao/ipcshmem/ipcshmem.c
 create mode 100644 include/linux/bao.h
 create mode 100644 include/uapi/linux/bao.h


base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
-- 
2.43.0