History

Dariusz Stojaczyk 6c0233c0a5 bdev_virtio: slight cleanup Fixed typos, updated comments and simplified the code. Change-Id: I7eaa7227518d376d86cd4a6eb0348f1efc7b47fd Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com> Reviewed-on: https://review.gerrithub.io/382024 Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com> Tested-by: SPDK Automated Test System <sys_sgsw@intel.com> Reviewed-by: Jim Harris <james.r.harris@intel.com>		2017-10-10 17:41:12 -04:00
..
rte_virtio	bdev_virtio: slight cleanup	2017-10-10 17:41:12 -04:00
bdev_virtio.c	bdev_virtio: slight cleanup	2017-10-10 17:41:12 -04:00
Makefile	rte_virtio: added virtio_queue.c/.h	2017-09-15 16:32:20 -04:00
README.md	bdev_virtio: specify limitations in README.md	2017-09-14 17:33:33 -04:00

README.md

SPDK virtio bdev module

This directory contains an experimental SPDK virtio bdev module. It currently supports very basic read/write operations for virtio-scsi drive. Currently it will only work with a single target with a single LUN.

It supports two different usage models:

PCI - This is the standard mode of operation when used in a guest virtual machine, where QEMU has presented the virtio-scsi controller as a virtual PCI device. The virtio-scsi controller might be implemented in the host OS by SPDK vhost-scsi. Kernel/QEMU vhost-scsi are not supported yet.
User vhost - Can be used to connect to an SPDK vhost-scsi target running on the same host.

Note that 1GB hugepages is pretty much required to use this driver in user-vhost mode. vhost protocol requires passing a file descriptor for each region of memory being shared with the vhost target. Since DPDK opens every huge page explicitly, it is fairly limited on how many file descriptors it can pass due to the VHOST_MEMORY_MAX_NREGIONS limit of 8.

Use the following configuration file snippet to enumerate a virtio-scsi PCI device and present its LUNs as bdevs.

[Virtio]
  Dev Pci

Use the following configuration file snippet to enumerate an SPDK vhost-scsi controller and present its LUNs as bdevs. In this case, the SPDK vhost-scsi target has created an SPDK vhost-scsi controller which is accessible through the /tmp/vhost.0 domain socket.

[Virtio]
  Dev User /tmp/vhost.0

Todo:

Support multiple PCI devices, including specifying the PCI device by PCI bus/domain/function.
Add unmap support.
Add I/O channel support. Includes requesting correct number of queues (based on core count). Fail device initialization if not enough queues can be allocated.
Add RPCs.
Break out the "rte_virtio" code into a separate library that is not linked directly to the bdev module. This would allow that part of the code to potentially get used and tested outside of the SPDK bdev framework.
Check for allocation failures in bdev_virtio.c code.
Add SPDK_TRACELOGs.
Add virtio-blk support. This will require some rework in the core virtio code (in the rte_virtio subdirectory) to allow for multiple device types.
Bottom out on whether we should have one virtio driver to cover both scsi and blk. If these should be separate, then this driver should be renamed to something scsi specific.
Add reset support.
Finish cleaning up "eth" references. This includes filenames like virtio_ethdev.c and "eth" in various API calls.
Understand and handle queue full conditions.
Clear interrupt flag for completions - since we are polling, we do not need the virtio-scsi backend to signal completion.
Check interrupt flag for submission. If the backend requires an interrupt, we need to signal it.
Change read/write to use READ_16/WRITE_16 to handle LBA > 4G. We can add a basic check and bail during enumeration if INQUIRY indicates the LUN does not support >= SBC-3.
Automated test scripts for both PCI and vhost-user scenarios.
Document Virtio config file section in examples. Should wait on this until enough of the above items are implemented to consider this module as ready for more general use.
Specify the name of the bdev in the config file (and RPC) - currently we just hardcode a single bdev name "Virtio0".