Re: [Qemu-devel] [PATCH] vhost-vsock: report QMP event when set running

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Aug 01, 2019 at 05:25:04PM +0200, Markus Armbruster wrote:
> Ning Bo <ning.bo9@zte.com.cn> writes:
> 
> > Report vsock running event so that the upper application can
> > control boot sequence.
> > see https://github.com/kata-containers/runtime/pull/1918
> 
> Please provide a more complete summary of the use case in the commit
> message.  What exactly is the problem?  What is the proposed solution,
> and how does it make use of the new event?
> 
> > Signed-off-by: Ning Bo <ning.bo9@zte.com.cn>


Also it would seem that it should be possible to detect
port listen state change just by trying to connect to it.
Why isn't that an option?



> > ---
> >  hw/virtio/vhost-vsock.c |  3 +++
> >  qapi/char.json          | 22 ++++++++++++++++++++++
> >  2 files changed, 25 insertions(+)
> >
> > diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c
> > index 0371493..a5920fd 100644
> > --- a/hw/virtio/vhost-vsock.c
> > +++ b/hw/virtio/vhost-vsock.c
> > @@ -22,6 +22,7 @@
> >  #include "qemu/iov.h"
> >  #include "qemu/module.h"
> >  #include "monitor/monitor.h"
> > +#include "qapi/qapi-events-char.h"
> >  
> >  enum {
> >      VHOST_VSOCK_SAVEVM_VERSION = 0,
> > @@ -68,6 +69,8 @@ static int vhost_vsock_set_running(VHostVSock *vsock, int start)
> >      if (ret < 0) {
> >          return -errno;
> >      }
> > +    qapi_event_send_vsock_running(vsock->conf.guest_cid, start != 0);
> > +
> >      return 0;
> >  }
> >  
> > diff --git a/qapi/char.json b/qapi/char.json
> > index a6e81ac..7b746e3 100644
> > --- a/qapi/char.json
> > +++ b/qapi/char.json
> > @@ -570,3 +570,25 @@
> >  { 'event': 'VSERPORT_CHANGE',
> >    'data': { 'id': 'str',
> >              'open': 'bool' } }
> > +
> > +##
> > +# @VSOCK_RUNNING:
> > +#
> > +# Emitted when the guest changes the vsock status.
> > +#
> > +# @cid: guest context ID
> > +#
> > +# @running: true if the vsock is running
> > +#
> > +# Since: v4.2
> > +#
> > +# Example:
> > +#
> > +# <- { "event": "VSOCK_RUNNING",
> > +#      "data": { "cid": "123456", "running": true },
> > +#      "timestamp": { "seconds": 1401385907, "microseconds": 422329 } }
> > +#
> > +##
> > +{ 'event': 'VSOCK_RUNNING',
> > +  'data': { 'cid': 'uint64',
> > +            'running': 'bool' } }
> 
> Can you explain why you put this into char.json?
> 
> The event traces successful calls of vhost_vsock_set_running().  I have
> no idea what vhost_vsock_set_running() does (pardon my ignorance).  Can
> you point me to a specification?
> 
> Its @start parameter is int.  The event's @running is bool.  Zero gets
> mapped to false, non-zero to true.  Are you sure all non-zero values are
> equivalent, and will remain equivalent?


Allowing guest to emit events at a high speed