Re: [PATCH] Revert "virtio-scsi: Send "REPORTED LUNS CHANGED" sense data upon disk hotplug events"

[Stefano Garzarella]

Hi Mark

On Fri, Jul 7, 2023 at 5:58 PM Mark Kanda <mark.kanda@oracle.com> wrote:

[...]

> >> On 7/5/2023 2:15 AM, Stefano Garzarella wrote:
> >>> This reverts commit 8cc5583abe6419e7faaebc9fbd109f34f4c850f2.
> >>>
> >>> That commit causes several problems in Linux as described in the BZ.
> >>> In particular, after a while, other devices on the bus are no longer
> >>> usable even if those devices are not affected by the hotunplug.
> >>> This may be a problem in Linux, but we have not been able to identify
> >>> it so far. So better to revert this patch until we find a solution.
> >>>
> >>> Also, Oracle, which initially proposed this patch for a problem with
> >>> Solaris, seems to have already reversed it downstream:
> >>>     https://linux.oracle.com/errata/ELSA-2023-12065.html
> >>>
> >>> Suggested-by: Thomas Huth <thuth@redhat.com>
> >>> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2176702
> >>> Cc: qemu-stable@nongnu.org
> >>> Cc: Mark Kanda <mark.kanda@oracle.com>
> >>> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> >>
> >> Reviewed-by: Mark Kanda <mark.kanda@oracle.com>
> >>
> >
> > Thanks for the review.
> >
> > By any chance do you have any information you can share regarding
> > [Orabug: 34905939] mentioned in the errata?
> >
> > I'd like to better understand why this patch created problems in Linux,
> > but solved others in Solaris.
>
> Apologies for the delay. I unfortunately can't provide any useful details. We
> had a brief internal discussion about whether the Solaris or Linux driver was
> technically correct per SCSI spec (I'm not sure we came to a conclusion). In 
> any
> case, we ultimately decided it didn't matter because we cannot tolerate a 
> Linux
> regression, and therefore Solaris should change to behave like Linux.

Okay, thanks for the update.

We'll try to figure out what goes wrong in Linux, but if we can't we
should merge this before the next release.

Thanks,
Stefano