Re: [PATCH v3 0/3] scsi: virtio_scsi: move INIT_WORK calls to virtscsi_init

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Thu, Mar 19, 2026 at 10:19:00PM -0400, Martin K. Petersen wrote:
> > This patch avoids a kernel warning that may occur if a virtio_scsi
> > controller is detached immediately following a disk detach. See the
> > commit message for details. The following are instructions to
> > produce the warning (without the proposed patch).
> 
> A few issues were flagged. Please review:
> 
>   https://sashiko.dev/#/patchset/20260316153341.2062278-1-jdaley%40linux.ibm.com

Hi Joshua,
I am responding to the following sashiko review comment (haven't figured
out a way to reply in the web UI or via direct email to sashiko). I feel
responsible for this one since I suggested the change that sashiko is
questioning. I haven't looked at the other review comments, please
triage them yourself.

From Sashiko:
> Does this code violate the virtio-scsi specification?
>
> The specification mandates that a driver must not place buffers into the
> event virtqueue if neither VIRTIO_SCSI_F_HOTPLUG nor VIRTIO_SCSI_F_CHANGE
> has been negotiated.
>
> By completely removing the VIRTIO_SCSI_F_HOTPLUG check without expanding it
> to check for VIRTIO_SCSI_F_CHANGE, could this unconditionally populate the
> event queue and cause strict implementations to reject the buffers or
> transition the device into a broken state?

No, this is a hallucination. The spec does not mandate that a driver
must not place buffers into the event virtqueue when neither
VIRTIO_SCSI_F_HOTPLUG nor VIRTIO_SCSI_F_CHANGE has been negotiated:
https://docs.oasis-open.org/virtio/virtio/v1.4/virtio-v1.4.html#x1-4510006

The event virtqueue still serves a purpose when both
VIRTIO_SCSI_F_HOTPLUG and VIRTIO_SCSI_F_CHANGE are not negotiated. For
example, see "Asynchronous notification subscription" and the
VIRTIO_SCSI_T_ASYNC_NOTIFY event type.

Stefan

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