On Wed, 2019-09-18 at 10:39 +0100, Stefan Hajnoczi wrote:
>
> > vu_check_queue_msg_file(VuDev *dev, VhostUserMsg *vmsg)
> > {
> > int index = vmsg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
> > + bool nofd = vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
> >
> > if (index >= dev->max_queues) {
> > vmsg_close_fds(vmsg);
> > @@ -927,8 +928,12 @@ vu_check_queue_msg_file(VuDev *dev, VhostUserMsg *vmsg)
> > return false;
> > }
> >
> > - if (vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK ||
> > - vmsg->fd_num != 1) {
> > + if (nofd) {
> > + vmsg_close_fds(vmsg);
> > + return true;
> > + }
So in this particular code you quoted, I actually just aligned to have
the same "bool nofd" variable - and I made it return "true" when no FD
was given.
It couldn't make use of what you proposed:
> With the following change to vmsg_close_fds():
>
> for (i = 0; i < vmsg->fd_num; i++) {
> close(vmsg->fds[i]);
> }
> + for (i = 0; i < sizeof(vmsg->fd_num) / sizeof(vmsg->fd_num[0]); i++) {
> + vmsg->fds[i] = -1;
> + }
> + vmsg->fd_num = 0;
>
> ...the message handler functions below can use vmsg->fds[0] (-1) without
> worrying about NOFD. This makes the code simpler.
because fd_num != 1 leads to the original code returning false, which
leads to the ring not getting started in vu_set_vring_kick_exec(). So we
need the special code here, can be argued if I should pull out the test
into the "bool nofd" variable or not ... *shrug*
The changes in vu_set_vring_kick_exec() and vu_set_vring_err_exec()
would indeed then not be necessary, but in vu_set_vring_call_exec() we
should still avoid the eventfd_write() if it's going to get -1.
So, yeah - could be a bit simpler there. I'd say being explicit here is
easier to understand and thus nicer, but your (or Michael's I guess?)
call.
johannes
