Hello,
I will try to send this upstream early next week.
V2: - Don't limit get/set config to 8 bytes only. - Improved direct/indirect message handling. - Take care of EBUSY error during indirect message. - Static assertions.
-------------------------8<-------------------------
Hello,
This RFC series introduces support for a new Virtio transport type: "virtio-msg", as proposed in [1]. Unlike existing transport types like virtio-mmio or virtio-pci which rely on memory-mapped registers, virtio-msg implements transport operations via structured messages. Those messages can be transported through different mechanisms such as mailboxes, shared memory based FIFO or specific protocols such as FF-A on Arm.
This series includes: - Core virtio-msg transport support. - Two message transport bus implementations: - virtio-msg-ffa: based on ARM's Firmware Framework for Arm (FF-A). - virtio-msg-loopback: a loopback device for testing and validation.
The code is available here for reference: [3] and virtio-msg loopback test setup is explained here: [2].
This series is based on v6.16-rc6 and depends on commit [4] from linux-next.
### Memory Mapping and Reserved Memory Usage
The first two patches enhance the reserved-memory subsystem to support attaching struct device`s that do not originate from DT nodes—essential for virtual or dynamically discovered devices like the FF-A or loopback buses.
This reserved-memory region enables: - Restricting all DMA-coherent and streaming DMA memory to a controlled range. - Allowing the remote endpoint to pre-map this memory, reducing runtime overhead. - Preventing unintentional data leaks, since memory is typically shared at page granularity. - For the loopback bus, it restricts the portion of kernel memory that can be mapped into userspace, improving safety.
Device association with reserved-memory regions is based on DT node naming conventions, such as vmsglb@ or vmsgffa@, similar to the remoteproc framework’s approach.
Feedback on the design, API, and approach is welcome.
-- Viresh
[1] https://lore.kernel.org/all/20250620224426.3923880-2-bill.mills@linaro.org/ [2] https://linaro.atlassian.net/wiki/spaces/HVAC/pages/30104092673 [3] git://git.kernel.org/pub/scm/linux/kernel/git/vireshk/linux.git virtio/msg-rfc-v1 [4] From linux-next: 5be53630b4f0 virtio-mmio: Remove virtqueue list from mmio device
Viresh Kumar (6): of: reserved-memory: Add reserved_mem_device_init() of: reserved-memory: Add of_reserved_mem_lookup_by_name virtio: Add support for virtio-msg transport virtio-msg: Add optional userspace interface for message I/O virtio-msg: Add support for FF-A (Firmware Framework for Arm) bus virtio-msg: Add support for loopback bus
MAINTAINERS | 7 + drivers/of/of_reserved_mem.c | 91 ++-- drivers/virtio/Kconfig | 34 ++ drivers/virtio/Makefile | 5 + drivers/virtio/virtio_msg.c | 611 +++++++++++++++++++++++++++ drivers/virtio/virtio_msg.h | 88 ++++ drivers/virtio/virtio_msg_ffa.c | 505 ++++++++++++++++++++++ drivers/virtio/virtio_msg_loopback.c | 323 ++++++++++++++ drivers/virtio/virtio_msg_user.c | 119 ++++++ include/linux/of_reserved_mem.h | 13 + include/uapi/linux/virtio_msg.h | 221 ++++++++++ include/uapi/linux/virtio_msg_ffa.h | 94 +++++ include/uapi/linux/virtio_msg_lb.h | 22 + 13 files changed, 2109 insertions(+), 24 deletions(-) create mode 100644 drivers/virtio/virtio_msg.c create mode 100644 drivers/virtio/virtio_msg.h create mode 100644 drivers/virtio/virtio_msg_ffa.c create mode 100644 drivers/virtio/virtio_msg_loopback.c create mode 100644 drivers/virtio/virtio_msg_user.c create mode 100644 include/uapi/linux/virtio_msg.h create mode 100644 include/uapi/linux/virtio_msg_ffa.h create mode 100644 include/uapi/linux/virtio_msg_lb.h