Re: [Qemu-devel] [PATCH] virtio-blk: Drop x-data-plane option

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Mon, Dec 07, 2015 at 05:10:26PM +0000, Peter Maydell wrote:
> On 7 December 2015 at 15:19, Paolo Bonzini <pbonzini@redhat.com> wrote:
> >
> >
> > On 07/12/2015 14:02, Fam Zheng wrote:
> >> On Mon, 12/07 12:29, Cornelia Huck wrote:
> >>> On Mon,  7 Dec 2015 18:59:27 +0800
> >>> Fam Zheng <famz@redhat.com> wrote:
> >>>
> >>>> The official way of enabling dataplane is through the "iothread"
> >>>> property that references an iothread object created by "-object
> >>>> iothread".  Since the old "x-data-plane=on" way now even crashes, it's
> >>>> probably easier to just drop it:
> >>>>
> >>>> $ qemu-system-x86_64 -drive file=null-co://,id=d0,if=none \
> >>>>     -device virtio-blk-pci,drive=d0,x-data-plane=on
> >>>>
> >>>> ERROR:/home/fam/work/qemu/qom/object.c:1515:
> >>>> object_get_canonical_path_component: assertion failed: (obj->parent != NULL)
> >>>> Aborted
> >>>
> >>> Do we understand yet why this crashes, btw?
> >>
> >> I think it's because with x-data-plane=on, virtio-blk initialize an object that
> >> doesn't have a parent, therefore it doesn't have a valid "canonical path
> >> component" thing, which is different from objects created with "-object" CLI.
> >> I'm not very familiar with the QOM semantics here.
> >>
> >>>
> >>>>
> >>>> Signed-off-by: Fam Zheng <famz@redhat.com>
> >>>> ---
> >>>>  hw/block/dataplane/virtio-blk.c | 15 ++-------------
> >>>>  hw/block/virtio-blk.c           |  1 -
> >>>>  include/hw/virtio/virtio-blk.h  |  1 -
> >>>>  3 files changed, 2 insertions(+), 15 deletions(-)
> >>>>
> >>>
> >>> No general objection to removing x-data-plane; but this probably wants
> >>> a mention on the changelog as x-data-plane has been described in
> >>> various howtos etc. over the years.
> >>
> >> Yes, that is a good point.  I don't know if it's too rushing in removing it for
> >> 2.5 (this is just posted as one option) and we'll have to count on QOM experts
> >> for the fix, if it is.
> >
> > The solution would be to add object_property_add_child to
> > virtio_blk_data_plane_create, between object_initialize and
> > user_creatable_complete.  But I think this patch is ok for 2.5.
> 
> Paolo asked me to apply this to master, so I have done so.

Okay.  I will do my best to communicate that x-data-plane is gone.

Stefan

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