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8bb862d415
vhost-device/crates/scsi
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Erik Schilling 8bb862d415 scsi: add some helper scripts for testing 
This provides some tooling for running blktests. The README.md contains
documentation about the architecture.

I am seeing some race-conditions that sometimes lead to boot
freezes [1], so this is not really ready for automatic evaluation during
a CI pipeline.

[1] https://linaro.atlassian.net/browse/ORKO-37

Signed-off-by: Erik Schilling <erik.schilling@linaro.org>
Link: https://linaro.atlassian.net/browse/ORKO-17
2023-06-05 14:55:32 +05:30
..
src scsi: add support for SYNCHRONIZE CACHE(10) 2023-06-05 14:55:32 +05:30
test scsi: add some helper scripts for testing 2023-06-05 14:55:32 +05:30
ARCHITECTURE.md scsi: Add documentation 2023-06-05 14:55:32 +05:30
Cargo.toml scsi: Initial boilerplate. 2023-06-05 14:55:32 +05:30
CHANGELOG.md scsi: Add virtio daemon 2023-06-05 14:55:32 +05:30
README.md scsi: Add documentation 2023-06-05 14:55:32 +05:30

README.md

vhost-user-scsi

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

Usage

Run the vhost-user-scsi daemon:

vhost-user-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 meory
  -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.