Re: [Qemu-devel] [PATCH 2/2] virtio-scsi: Implement hotplug support for virtio-scsi

[Stefan Hajnoczi]

On Wed, Jun 20, 2012 at 7:47 AM, Cong Meng <address@hidden> wrote:
> Implement the hotplug() and hot_unplug() interfaces in virtio-scsi, by signal
> the virtio_scsi.ko in guest kernel via event virtual queue.
>
> The counterpart patch of virtio_scsi.ko will be sent soon in another thread.
>
> Signed-off-by: Cong Meng <address@hidden>
> Signed-off-by: Sen Wang <address@hidden>
> ---
>  hw/virtio-scsi.c |   72 +++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 files changed, 69 insertions(+), 3 deletions(-)

I compared against the virtio-scsi specification and this looks good:
http://ozlabs.org/~rusty/virtio-spec/virtio-0.9.5.pdf

Dropped events and event throttling are not implemented by this patch.
 This means that the guest can miss events if it runs out of event
queue elements.  A scenario that might be able to trigger this is if
multiple LUNs are hotplugged in a single QEMU monitor callback.

Implementing dropped events is easy in hw/virtio-scsi.c.  Keep a bool
or counter of dropped events and report them when the guest kicks us
with a free event element (virtio_scsi_handle_event).

Stefan