Default Comment by Bridge
** Attachment added: "proposed backport"
https://bugs.launchpad.net/bugs/1967814/+attachment/5577049/+files/backport_qemu-4.2.mbox
** Changed in: ubuntu
Assignee: (unassigned) => Skipper Bug Screeners (skipper-screen-team)
** Package changed: ubuntu => linux (Ubuntu)
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https://bugs.launchpad.net/bugs/1967814
Title:
Ubuntu 20.04.3 - ilzlnx3g1 - virtio-scsi devs on KVM guest having
miscompares on disktests when there is a failed path.
Status in linux package in Ubuntu:
New
Bug description:
== Comment: #63 - Halil Pasic <[email protected]> - 2022-03-28 17:33:34 ==
I'm pretty confident I've figured out what is going on.
From the guest side, the decision whether the SCSI command was completed
successfully or not comes down to looking at the sense data. Prior to commit
a108557bbf ("scsi: inline sg_io_sense_from_errno() into the callers."), we
don't
build sense data as a response to seeing a host status presented by the host
SCSI stack (e.g. kernel).
Thus when the kernel tells us that a given SCSI command did not get
completed via
SCSI_HOST_TRANSPORT_DISRUPTED or SCSI_HOST_NO_LUN, we end up fooling the
guest into believing that the command completed successfully.
The guest kernel, and especially virtio and multipath are at no fault
(AFAIU). Given these facts, it isn't all that surprising, that we end
up with corruptions.
All we have to do is do backports for QEMU (when necessary). I didn't
investigate vhost-scsi -- my guess is, that it ain't affected.
How do we want to handle the back-ports?
== Comment: #66 - Halil Pasic <[email protected]> - 2022-04-04 05:36:33 ==
This is a proposed backport containing 7 patches in mbox format. I tried to
pick patches sanely, and all I had to do was basically resolving merge
conflicts.
I have to admit I have no extensive experience in doing such invasive
backports, and my knowledge of the QEMU SCSI stack is very limited. I
would be happy if the Ubuntu folks would have a good look at this, and
if possible improve on it.
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