Re: [Qemu-devel] virtio 1 issues

[Cornelia Huck]

On Fri, 07 Aug 2015 13:07:35 +0800
Jason Wang <address@hidden> wrote:

> > 2. ring resizing is broken - it actually has a comment:
> >         /* TODO: need a way to put num back on reset. */
> > guest that runs out of memory might down-size the ring.
> > Afterwards, ring size won't come back up after reset - not nice.
> >
> 
> Then we need a new field to keep track the original queue size and
> migrate this.

virtio-ccw neatly sidesteps it by not implementing ring size changes at
all :)

But it isn't really all good, see

/* TODO: Add interface to handle vring.num changing */

We either need to implement this or fence off changing the ring size, I
guess.

> 
> >
> > Given that the modern layout is disabled by default,
> > I don't think these are release blockers.
> >
> 
> Yes and looks like we need a new subsection and transport specific
> callbacks to fix above?

Agreed, it's not urgent as virtio-1 is not yet the default (and not
even enabled for ccw).

I'm not sure we need transport-specific callbacks. Shouldn't the core
be able to track initial and actual size (and migrate in an optional
subsection), as long as the transports use defined interfaces to
interact with it?