Re: [PATCH v2 5/5] vhost: add device started check in migration set log

[Jason Wang]

On 2020/5/13 下午5:47, Dima Stepanov wrote:
> > >      case CHR_EVENT_CLOSED:
> > >          /* a close event may happen during a read/write, but vhost
> > >           * code assumes the vhost_dev remains setup, so delay the
> > >           * stop & clear to idle.
> > >           * FIXME: better handle failure in vhost code, remove bh
> > >           */
> > >          if (s->watch) {
> > >              AioContext *ctx = qemu_get_current_aio_context();
> > >
> > >              g_source_remove(s->watch);
> > >              s->watch = 0;
> > >              qemu_chr_fe_set_handlers(&s->chr, NULL, NULL, NULL, NULL,
> > >                                       NULL, NULL, false);
> > >
> > >              aio_bh_schedule_oneshot(ctx, chr_closed_bh, opaque);
> > >          }
> > >          break;
> > >
> > > I think it's time we dropped the FIXME and moved the handling to common
> > > code. Jason? Marc-André?
> > I agree. Just to confirm, do you prefer bh or doing changes like what is
> > done in this series? It looks to me bh can have more easier codes.
> Could it be a good idea just to make disconnect in the char device but
> postphone clean up in the vhost-user-blk (or any other vhost-user
> device) itself? So we are moving the postphone logic and decision from
> the char device to vhost-user device. One of the idea i have is as
> follows:
>    - Put ourself in the INITIALIZATION state
>    - Start these vhost-user "handshake" commands
>    - If we got a disconnect error, perform disconnect, but don't clean up
>      device (it will be clean up on the roll back). I can be done by
>      checking the state in vhost_user_..._disconnect routine or smth like it


Any issue you saw just using the aio bh as Michael posted above.

Then we don't need to deal with the silent vhost_dev_stop() and we will 
have codes that is much more easier to understand.

Thank


>    - vhost-user command returns error back to the _start() routine
>    - Rollback in one place in the start() routine, by calling this
>      postphoned clean up for the disconnect