Re: [Xen-devel] [PATCH 1/2] libxl: Add a version check of QEMU for QMP commands

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Tue, Mar 13, 2018 at 05:40:08PM +0000, Wei Liu wrote:
> On Tue, Mar 13, 2018 at 11:13:17AM +0000, Anthony PERARD wrote:
> > On connection to QEMU via QMP, the version of QEMU is provided, store it
> > for later use.
> > 
> > Add a function qmp_qemu_check_version that can be used to check if QEMU
> > is new enough for certain fonctionnality. This will be used in a moment.
> > 
> > As it's a static function, it is commented out until first use, which is
> > in the next patch.
> > 
> > Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> > ---
> >  tools/libxl/libxl_qmp.c | 31 ++++++++++++++++++++++++++++++-
> >  1 file changed, 30 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
> > index eab993aca9..b1c6598cf7 100644
> > --- a/tools/libxl/libxl_qmp.c
> > +++ b/tools/libxl/libxl_qmp.c
> > @@ -75,6 +75,11 @@ struct libxl__qmp_handler {
> >  
> >      int last_id_used;
> >      LIBXL_STAILQ_HEAD(callback_list, callback_id_pair) callback_list;
> > +    struct {
> > +        int major;
> > +        int minor;
> > +        int micro;
> > +    } version;
> >  };
> >  
> >  static int qmp_send(libxl__qmp_handler *qmp,
> > @@ -296,9 +301,22 @@ static int qmp_handle_response(libxl__gc *gc, 
> > libxl__qmp_handler *qmp,
> >      LOGD(DEBUG, qmp->domid, "message type: %s", 
> > libxl__qmp_message_type_to_string(type));
> >  
> >      switch (type) {
> > -    case LIBXL__QMP_MESSAGE_TYPE_QMP:
> > +    case LIBXL__QMP_MESSAGE_TYPE_QMP: {
> > +        const libxl__json_object *o;
> > +        o = libxl__json_map_get("QMP", resp, JSON_MAP);
> > +        o = libxl__json_map_get("version", o, JSON_MAP);
> > +        o = libxl__json_map_get("qemu", o, JSON_MAP);
> > +        qmp->version.major = libxl__json_object_get_integer(
> > +            libxl__json_map_get("major", o, JSON_INTEGER));
> > +        qmp->version.minor = libxl__json_object_get_integer(
> > +            libxl__json_map_get("minor", o, JSON_INTEGER));
> > +        qmp->version.micro = libxl__json_object_get_integer(
> > +            libxl__json_map_get("micro", o, JSON_INTEGER));
> > +        LOGD(DEBUG, qmp->domid, "QEMU version: %d.%d.%d",
> > +             qmp->version.major, qmp->version.minor, qmp->version.micro);
> >          /* On the greeting message from the server, enable QMP 
> > capabilities */
> >          return enable_qmp_capabilities(qmp);
> > +    }
> 
> Are those fields available in QMP in all the versions we care about?

I don't care if the field is available or not, the result would be a
QEMU version -1.-1.-1 This is why I did not do any check here to find
out if a particular value exist.  But the version field is part of the
QMP protocol, so it should be there.

Also yes, the field is available in all QEMU version we care about, e.i.
QEMU 2.11 and later. That information is not usefull for older version
of QEMU.

> If so, 
> 
> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

Thanks,

-- 
Anthony PERARD

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