Re: [Qemu-devel] [PATCH 1/2] hostmem: fix QEMU crash by 'info memdev'

[Xiao Guangrong]

On 07/13/2016 07:37 PM, Paolo Bonzini wrote:
> On 13/07/2016 13:29, Markus Armbruster wrote:
> > > > I'm curious about one thing.  Eric/Markus, it would be nice to open code
> > > > the visit of the list with
> > > >
> > > >      visit_start_list(v, name, NULL, 0, &err);
> > > >      if (err) {
> > > >          goto out;
> > > >      }
> > > >      ...
> > > >      visit_type_uint16(v, name, &value, &err);
> > > >      visit_next_list(v, NULL, 0);
> > > >      ...
> > > >      visit_end_list(v, NULL);
> > > >
> > > > We know here that on the other side there is an output visitor.
> > > > However, it doesn't work because visit_next_list asserts that tail ==
> > > > NULL.  Would it be easy to support this idiom, and would it make sense
> > > > to extend it to other kinds of visitor?
> > visit_next_list() asserts tail != NULL because to protect the
> > next_list() method.  qmp_output_next_list() dereferences tail.
> >
> > Note that you don't have to call visit_next_list() in a virtual visit.
> > For an example, see prop_get_fdt().  Good enough already?
>
> Yes, definitely!  I'm queueing Guangrong's patch because it fixes a
> crash and the leak existed before, but without next_list we can indeed
> visit a "virtual" list and fix the leak.  It can be done during the -rc
> period.

So you want to build uint16List list and save it as a "virtual" list in
host_memory_backend_get_host_nodes(), then its caller can directly fetch
this 'virtual' list from the visit?