Changing the affected package from "linux (Ubuntu)" (kernel) to "qemu
(Ubuntu)" as affected package, since the attached patch set is for qemu.
** Package changed: linux (Ubuntu) => qemu (Ubuntu)
** Also affects: qemu
Importance: Undecided
Status: New
** No longer affects: qemu
** Also affects: ubuntu-z-systems
Importance: Undecided
Status: New
** Changed in: ubuntu-z-systems
Assignee: (unassigned) => Skipper Bug Screeners (skipper-screen-team)
** Changed in: qemu (Ubuntu)
Assignee: Skipper Bug Screeners (skipper-screen-team) => Canonical Server
Team (canonical-server)
** Changed in: ubuntu-z-systems
Importance: Undecided => High
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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 Ubuntu on IBM z Systems:
New
Status in qemu package in Ubuntu:
New
Status in qemu source package in Focal:
New
Bug description:
== Comment: #63 - Halil Pasic <pa...@de.ibm.com> - 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 <pa...@de.ibm.com> - 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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