pxcloud/vhost-device
5
0
Fork 0
mirror of https://github.com/rust-vmm/vhost-device.git synced 2026-01-07 11:37:40 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity
decfd8bd73
vhost-device/crates/scsi/ARCHITECTURE.md
Stefano Garzarella 6305c66f22 scsi: replaced some leftover of vhost-user-scsi 
There was some reference left in the documentation and sources to
"vhost-user-scsi" that we had changed during the rebase.
Let's change them to "vhost-device-scsi".

Everything should be safe.

We leave "vhost-user-scsi" in
crates/scsi/src/scsi/emulation/response_data.rs because it looks like
an identifier with some constant size. We will fix in the future.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
2023-07-24 12:15:23 +05:30

1.7 KiB
Raw Blame History

vhost-device-scsi architecture

Rough outline of the different pieces and how they fit together:

scsi/mod.rs

This defines the Target trait, which represents a SCSI target. The code in this file is independent from:

  • A particular SCSI implementation: Currently, we have one implementation of Target, which emulates the SCSI commands itself; but future implementations could provide pass-through to an iSCSI target or SCSI devices attached to the host.
  • A particular SCSI transport: Nothing in src/scsi/* knows anything about virtio; this is helpful for maintainability, and also allows our SCSI emulation code to be reusable as, for example, an iSCSI target. To this end, the Target trait is generic over a Read and Write that it uses for SCSI data transfer. This makes testing easy: we can just provide a Vec<u8> to write into.

scsi/emulation/*.rs

This is the SCSI emulation code, which forms the bulk of the crate. It provides EmulatedTarget, an implementation of Target. EmulatedTarget, in turn, looks at the LUN and delegates commands to an implementation of LogicalUnit. In most cases, this will be BlockDevice; there's also MissingLun, which is used for responding to commands to invalid LUNs.

Currently, there is no separation between commands defined in the SPC standard (commands shared by all device types) and the SBC standard (block-device specific commands). If we ever implemented another device type (CD/DVD seems most likely), we'd want to separate those out.

As noted above, the emulation code knows nothing about virtio.

src/{main,virtio}.rs

This code handles vhost-user, virtio, and virtio-scsi; it's the only part of the crate that knows about these protocols.