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

[Fam Zheng]

On Mon, 12/07 12:29, Cornelia Huck wrote:
> On Mon,  7 Dec 2015 18:59:27 +0800
> Fam Zheng <address@hidden> 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 <address@hidden>
> > ---
> >  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.

Fam