Re: [Xen-devel] [Qemu-devel] qemu mainline regression with xen-unstable: unable to start QMP

[Fabio Fantoni <fabio.fantoni@xxxxxxx>]

Il 05/06/2015 00:20, Don Slutz ha scritto:
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> On 06/04/15 18:10, Eric Blake wrote:
> > [adding Markus, as author of the regression]
> >
> > On 06/04/2015 03:59 PM, Don Slutz wrote:
> > > On 06/04/15 11:04, Fabio Fantoni wrote:
> > > > Today after trying xen-unstable build (tested many hours) of
> > > > some days ago I tried update qemu to latest development version
> > > > (from git master commit
> > > > 6fa6b312765f698dc81b2c30e7eeb9683804a05b) and seems that there
> > > > is a regression:
> > > > > xl create /etc/xen/W7.cfg Parsing config from
> > > > > /etc/xen/W7.cfg libxl: error:
> > > > > libxl_qmp.c:287:qmp_handle_error_response: received an error
> > > > > message from QMP server: QMP input object member 'id' is
> > > > > unexpected libxl: error:
> > > > > libxl_qmp.c:715:libxl__qmp_initialize: Failed to connect to
> > > > > QMP
> > > This is caused by:
> > >
> > > commit 65207c59d99f2260c5f1d3b9c491146616a522aa Author: Markus
> > > Armbruster <armbru@xxxxxxxxxx> Date:   Thu Mar 5 14:35:26 2015
> > > +0100
> > >
> > > monitor: Drop broken, unused asynchronous command interface
> > >
> > > The patch:
> > >
> > > >  From 1b0221078353870fe530e49de158cae205f9bce5 Mon Sep 17
> > > > 00:00:00 2001
> > > From: Don Slutz <dslutz@xxxxxxxxxxx> Date: Thu, 4 Jun 2015
> > > 17:04:42 -0400 Subject: [PATCH 01/14] monitor: Allow Xen's
> > > (broken) usage of asynchronous command interface.
Thanks, patch tested, solves the regression, I did successfull many xl 
command that use QMP.
> > > commit 65207c59d99f2260c5f1d3b9c491146616a522aa Author: Markus
> > > Armbruster <armbru@xxxxxxxxxx> Date:   Thu Mar 5 14:35:26 2015
> > > +0100
> > >
> > > monitor: Drop broken, unused asynchronous command interface
> > >
> > > Breaks Xen.  Add a hack un unbreak it.
> > s/un /to /
> Sigh, will fix.
>
> > > Xen is only doing synchronous commands, but is including an id.
> > QMP also uses id, but apparently removes it up front before calling
> > into this function; so another fix would be having xen remove it up
> > front.
> Hopefully I will get to a change to Xen.  However getting the Xen
> change back-ported to enough version(s) will not be quick...
>
>
> > > Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx> --- monitor.c | 9
> > > +++++++++ 1 file changed, 9 insertions(+)
> > >
> > > diff --git a/monitor.c b/monitor.c index c7baa91..e9a0747 100644
> > > --- a/monitor.c +++ b/monitor.c @@ -4955,6 +4955,15 @@ static
> > > QDict *qmp_check_input_obj(QObject *input_obj, Error **errp)
> > > "arguments", "object"); return NULL; } +        } else if
> > > (!strcmp(arg_name, "id")) { +            /* +             * Fixup
> > > Xen's usage. Just ignore the "id". See point #5 +             *
> > > above.  This was an attempt at an asynchronous +             *
> > > command interface.  However commit +             *
> > > 65207c59d99f2260c5f1d3b9c491146616a522aa is +             *
> > > wrong. Xen does not expect an error when it passes in +
> > > * "id":1, so just continue to ignore it. +             */
> > The comment is a bit verbose, particularly since 'id' is a
> > well-established usage pattern in QMP.  Also, we don't need to call
> > out why it changed in the comment here, the commit message is
> > sufficient for that.
> Ok, will also see if Markus has anything to say.
>
>     -Don Slutz
>
> > > } else { error_set(errp, QERR_QMP_EXTRA_MEMBER, arg_name); return
> > > NULL;
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