Hi all, this RFC series adds Rust bindings for Virtio drivers (frontends in virtio parlance).
As a PoC, it also adds a sample virtio-rtc driver which performs capability discovery through the virtqueue without registering any clock. Before I send a cleaned-up non-RFC I would like some initial feedback (i.e. is it something the upstream wants?) This was tested with the rust-vmm vhost-device-rtc device backend that I wrote[^0]: [^0]: https://github.com/rust-vmm/vhost-device/tree/main/vhost-device-rtc Instructions: Run the daemon in a separate terminal: $ cargo run --bin vhost-device-rtc -- -s /tmp/rtc.sock Then run the VM: $ qemu-system-aarch64 \ -machine type=virt,virtualization=off,acpi=on \ -cpu host \ -smp 8 \ -accel kvm \ -drive if=virtio,format=qcow2,file=./debian-13-nocloud-arm64-daily.qcow2 \ -device virtio-net-pci,netdev=unet \ -device virtio-scsi-pci \ -serial mon:stdio \ -m 8192 \ -object memory-backend-memfd,id=mem,size=8G,share=on \ -numa node,memdev=mem \ -display none \ -vga none \ -kernel /path/to/linux/build/arch/arm64/boot/Image \ -device vhost-user-test-device,chardev=rtc,id=rtc,virtio-id=17,num_vqs=2,vq_size=1024 \ -chardev socket,path=/tmp/rtc.sock,id=rtc \ ... Example output: [ 1.105238] rust_virtio_rtc: Probe Rust virtio driver sample. [ 1.105645] rust_virtio_rtc: Found 1 vqs. [ 1.136050] rust_virtio_rtc: process_requestq got buf 16 bytes [ 1.136125] rust_virtio_rtc: Got response! Ok(RespCfg { head: ReqHead { msg_type: Le16(0), reserved: [0, 0, 0, 0, 0, 0] }, num_clocks: Le16(3), reserved: [0, 0, 0, 0, 0, 0] }) [ 1.136701] rust_virtio_rtc: Got response! Ok(RespClockCap { head: ReqHead { msg_type: Le16(0), reserved: [0, 0, 0, 0, 0, 0] }, clock_type: 3, leap_second_smearing: 0, flags: 0, reserved: [0, 0, 0, 0, 0] }) [ 1.136724] rust_virtio_rtc virtio0: cannot expose clock 0 (type 3, variant 0, flags 0) to userspace [ 1.137259] rust_virtio_rtc: Got response! Ok(RespRead { head: ReqHead { msg_type: Le16(0), reserved: [0, 0, 0, 0, 0, 0] }, clock_reading: Le64(1777890485031060388) }) [ 1.137277] rust_virtio_rtc: #0 clock reading = 1777890485031060388 [ 1.137749] rust_virtio_rtc: Got response! Ok(RespClockCap { head: ReqHead { msg_type: Le16(0), reserved: [0, 0, 0, 0, 0, 0] }, clock_type: 1, leap_second_smearing: 0, flags: 0, reserved: [0, 0, 0, 0, 0] }) [ 1.137769] rust_virtio_rtc virtio0: cannot expose clock 1 (type 1, variant 0, flags 0) to userspace [ 1.138247] rust_virtio_rtc: Got response! Ok(RespRead { head: ReqHead { msg_type: Le16(0), reserved: [0, 0, 0, 0, 0, 0] }, clock_reading: Le64(1777890485032086075) }) [ 1.138264] rust_virtio_rtc: #1 clock reading = 1777890485032086075 [ 1.138730] rust_virtio_rtc: Got response! Ok(RespClockCap { head: ReqHead { msg_type: Le16(0), reserved: [0, 0, 0, 0, 0, 0] }, clock_type: 2, leap_second_smearing: 0, flags: 0, reserved: [0, 0, 0, 0, 0] }) [ 1.138751] rust_virtio_rtc virtio0: cannot expose clock 2 (type 2, variant 0, flags 0) to userspace [ 1.139253] rust_virtio_rtc: Got response! Ok(RespRead { head: ReqHead { msg_type: Le16(0), reserved: [0, 0, 0, 0, 0, 0] }, clock_reading: Le64(338567896865557) }) [ 1.139270] rust_virtio_rtc: #2 clock reading = 338567896865557 Concerns - Notes - TODOs ======================== - Virtqueue lifetimes don't neatly apply to Rust as expected, so a lot of times we have to go through unsafe pointer dereferences (though which are guaranteed by Virtio subsystem to be valid, for example when a callback is called with the vq argument). There's a potential for misuse and definitely could use better thinking. - `struct virtio_device` is not reference-counted like other implemented device types in rust/kernel. Maybe we need to change C API first to make them reference counted, assuming this doesn't break anything? - Not sure if adding data smaller than PAGE_SIZE to virtqueue is safe (which current C code does a lot), so I made those allocations at least PAGE_SIZE. - The sample driver obviously conflicts with the C implementation, so this would either need to move out of samples/ or figure out some way to handle this in kbuild. - kernel::virtio module and its types need a few rustdoc examples that I will add in followup series - Note that the registration of RTC clocks etc in the sample driver is not done, I'm putting it off until I receive some feedback first. The sample driver otherwise does send and receive data from the virtqueue as a PoC. The code and data structures can be cleaned up further before followup series. PS: No LLMs used so any mistakes and goofs are solely written by me. Signed-off-by: Manos Pitsidianakis <[email protected]> --- Manos Pitsidianakis (6): rust/bindings: generate virtio bindings rust/helpers: add virtio.c rust: add virtio module rust/scatterlist: add SGEntry::init_one rust: impl interruptible waits for Completion samples/rust: Add sample virtio-rtc driver [WIP] MAINTAINERS | 9 + rust/bindings/bindings_helper.h | 5 + rust/helpers/helpers.c | 3 + rust/helpers/virtio.c | 35 +++ rust/kernel/lib.rs | 2 + rust/kernel/scatterlist.rs | 20 +- rust/kernel/sync/completion.rs | 39 ++++ rust/kernel/virtio.rs | 415 +++++++++++++++++++++++++++++++++++ rust/kernel/virtio/utils.rs | 65 ++++++ rust/kernel/virtio/virtqueue.rs | 181 ++++++++++++++++ samples/rust/Kconfig | 15 ++ samples/rust/Makefile | 1 + samples/rust/rust_virtio_rtc.rs | 470 ++++++++++++++++++++++++++++++++++++++++ 13 files changed, 1259 insertions(+), 1 deletion(-) --- base-commit: 028ef9c96e96197026887c0f092424679298aae8 change-id: 20260504-rust-virtio-8523b01dfdc2 Best regards, -- Manos Pitsidianakis <[email protected]>
