Re: [Qemu-devel] [PATCH 3/4] dataplane: change vring API to use VirtQueueElement

[Paolo Bonzini]

Il 05/12/2013 10:24, Stefan Hajnoczi ha scritto:
>> > 
>> > That's what already happens actually.  vring_push has
>> > 
>> > 
>> > +    g_slice_free(VirtQueueElement, elem);
>> > +
>> >      /* Don't touch vring if a fatal error occurred */
>> >      if (vring->broken) {
>> >          return;
>> > 
>> > in this patch and
>> > 
>> > +    for (i = 0; i < elem->out_num; i++) {
>> > +        vring_unmap(elem->out_sg[i].iov_base, false);
>> > +    }
>> > +
>> > +    for (i = 0; i < elem->in_num; i++) {
>> > +        vring_unmap(elem->in_sg[i].iov_base, true);
>> > +    }
>> > 
>> >      g_slice_free(VirtQueueElement, elem);
>> > 
>> > in the next one.
>> > 
>> > Though I admit vring_push isn't such a great name and API.  I can add
>> > instead a vring_free_element function.  Do you think vring_push should
>> > call it, or should the caller do that?
> I think vring_push() should free the VirtQueueElement.
> 
> We just need to expose vring_free_element() so that handle_notify() can
> call it without pushing bogus buffers back to the guest.

It's not pushing back bogus buffer, see the "if (vring->broken)" above.
 But if you prefer handle_notify() to call vring_free_element(), I can
of course do that.

Paolo