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

[Don Slutz <don.slutz@gmail.com>]

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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@redhat.com> 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@verizon.com> Date: Thu, 4 Jun 2015
>> 17:04:42 -0400 Subject: [PATCH 01/14] monitor: Allow Xen's
>> (broken) usage of asynchronous command interface.
>> 
>> commit 65207c59d99f2260c5f1d3b9c491146616a522aa Author: Markus
>> Armbruster <armbru@redhat.com> 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@verizon.com> --- 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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