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4c8a2bc3ac
vhost-device/crates/scsi
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Erik Schilling 4c8a2bc3ac scsi: Advertise support for CONFIG 
The config that we send is based on the current QEMU defaults
(as of 60ca584b8af0de525656f959991a440f8c191f12).

This allows testing using Alex Bennee's vhost-user-generic series and
will be required for hypervisors that do not come with the stubs that
QEMU has (eg: Xen).

Signed-off-by: Erik Schilling <erik.schilling@linaro.org>
Link: https://lore.kernel.org/all/20230414160433.2096866-1-alex.bennee@linaro.org/
2023-06-05 14:55:32 +05:30
..
src scsi: Advertise support for CONFIG 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.