Re: [Qemu-devel] [PATCH v4 1/3] i386/cpu: add crash-information QOM property

[Markus Armbruster <armbru@redhat.com>]

Eric Blake <eblake@redhat.com> writes:

> On 02/14/2017 12:25 AM, Denis V. Lunev wrote:
>> From: Anton Nefedov <anton.nefedov@virtuozzo.com>
>> 
>> Windows reports BSOD parameters through Hyper-V crash MSRs. This
>> information is very useful for initial crash analysis and thus
>> it would be nice to have a way to fetch it.
>> 
>> Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
>> Signed-off-by: Denis V. Lunev <den@openvz.org>
>> ---
>
>> +++ b/qapi-schema.json
>> @@ -5846,6 +5846,30 @@
>>    'data': [ 'pause', 'poweroff' ] }
>>  
>>  ##
>> +# @GuestPanicInformation:
>> +#
>> +# Information about a guest panic
>> +#
>> +# Since: 2.9
>> +##
>> +{'union': 'GuestPanicInformation',
>> + 'data': { 'hyper-v': 'GuestPanicInformationHyperV' } }
>> +
>
> Markus has been trying to eliminate the addition of new "simple unions"
> - while they are syntactically shorter in the .json file, they are
> bulkier over the wire with extra {} nesting, and more verbose in the C
> code, when compared to using a flat union instead.  I won't necessarily
> hold up this patch as-is, but if we are going to avoid new simple
> unions, we have to change this before 2.9 bakes in the {} nesting (we
> can convert a simple union to a flat union without breaking QMP
> back-compat, but it's messier than if we avoid the nesting to begin with).

We should not add new simple unions.  Please have a look at my
"[PATCH 0/2] Flatten simple unions where we still can".

Message-Id: <1486569864-17005-1-git-send-email-armbru@redhat.com>
https://lists.gnu.org/archive/html/qemu-devel/2017-02/msg01689.html