Accelerating non-standard disk types

[Raphael Norwitz <raphael.norwitz@nutanix.com>]

Hey Stefan,

We've been thinking about ways to accelerate other disk types such as
SATA and IDE rather than translating to SCSI and using QEMU's iSCSI
driver, with existing and more performant backends such as SPDK. We
think there are some options worth exploring:

[1] Keep using the SCSI translation in QEMU but back vDisks with a
vhost-user-scsi or vhost-user-blk backend device.
[2] Implement SATA and IDE emulation with vfio-user (likely with an SPDK
client?).
[3] We've also been looking at your libblkio library. From your
description in
https://lists.gnu.org/archive/html/qemu-devel/2021-04/msg06146.html it
sounds like it may definitely play a role here, and possibly provide the
nessesary abstractions to back I/O from these emulated disks to any
backends we may want?

We are planning to start a review of these options internally to survey
tradeoffs, potential timelines and practicality for these approaches. We
were also considering putting a submission together for KVM forum
describing our findings. Would you see any value in that?

Thanks,
Raphael