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vhost-device/vhost-device-scsi
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Manos Pitsidianakis 019e02b0f2 Replace ptr casts with typed cast() method 
Replace type inferred raw pointer casts with .cast() method calls to
make intent clearer.

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
2025-08-04 12:30:43 +02:00
..
src Replace ptr casts with typed cast() method 2025-08-04 12:30:43 +02:00
test Move all crates to workspace root 2023-10-16 12:03:57 +05:30
ARCHITECTURE.md Move all crates to workspace root 2023-10-16 12:03:57 +05:30
Cargo.toml scsi: fix test compilation 2025-07-09 09:48:35 +03:00
CHANGELOG.md chore: standardize changelogs 2024-07-24 19:37:19 +05:30
LICENSE-APACHE Move all crates to workspace root 2023-10-16 12:03:57 +05:30
LICENSE-BSD-3-Clause Move all crates to workspace root 2023-10-16 12:03:57 +05:30
README.md scsi: fix minor typos 2025-07-07 11:28:02 +03:00

README.md

vhost-device-scsi

This is a Rust implementation of a vhost-device-scsi daemon.

Usage

Run the vhost-device-scsi daemon:

vhost-device-scsi -r --socket-path /tmp/vhost-user-scsi.sock /path/to/image.raw /path/to/second-image.raw ...

Run QEMU:

qemu-system-x86_64 ... \
  -device vhost-user-scsi-pci,num_queues=1,param_change=off,chardev=vus \
  -chardev socket,id=vus,path=/tmp/vhost-user-scsi.sock \
  # must match total guest memory
  -object memory-backend-memfd,id=mem,size=384M,share=on \
  -numa node,memdev=mem

Limitations

We are currently only supporting a single request queue and do not support dynamic reconfiguration of LUN parameters (VIRTIO_SCSI_F_CHANGE).

Features

This crate is a work-in-progress. Currently, it's possible to mount and read up to 256 read-only raw disk images. Some features we might like to add at some point, roughly ordered from sooner to later:

  • Write support. This should just be a matter of implementing the WRITE command, but there's a bit of complexity around writeback caching we need to make sure we get right.
  • Support more LUNs. virtio-scsi supports up to 16384 LUNs per target. After 256, the LUN encoding format is different; it's nothing too complicated, but I haven't gotten around to implementing it.
  • Concurrency. Currently, we process SCSI commands one at a time. Eventually, it'd be a good idea to use threads or some fancy async/io_uring stuff to concurrently handle multiple commands. virtio-scsi also allows for multiple request queues, allowing the guest to submit requests from multiple cores in parallel; we should support that.
  • iSCSI passthrough. This shouldn't be too bad, but it might be a good idea to decide on a concurrency model (threads or async) before we spend too much time here.