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

[Mark Kanda]

Hi Stefano,

On 7/5/2023 7:36 AM, Stefano Garzarella wrote:
> Hi Mark,
>
> On Wed, Jul 05, 2023 at 07:28:05AM -0500, Mark Kanda 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.

Thanks/regards,
-Mark