Re: [Qemu-block] [Qemu-devel] [RFC PATCH 09/56] balloon: Make balloon size unsigned in QAPI/QMP

[Markus Armbruster]

"Dr. David Alan Gilbert" <address@hidden> writes:

> * Markus Armbruster (address@hidden) wrote:
>> Sizes should use QAPI type 'size' (uint64_t).  balloon parameter
>> @value is 'int' (int64_t).  qmp_balloon() implicitly converts to
>> ram_addr_t, i.e. uint64_t.  BALLOON_CHANGE parameter @actual and
>> BalloonInfo member @actual are also 'int'.
>> virtio_balloon_set_config() and virtio_balloon_stat() implicitly
>> convert from ram_addr_t.
>> 
>> Change all three to 'size', and adjust the code using them.
>> 
>> balloon now accepts size values between 2^63 and 2^64-1.  It accepts
>> negative values as before, because that's how the QObject input
>> visitor works for backward compatibility.
>> 
>> Doing the same for HMP's balloon deserves its own commit (the next
>> one).
>> 
>> BALLOON_CHANGE and query-balloon now report sizes above 2^63-1
>> correctly instead of their (negative) two's complement.
>> 
>> So does HMP's "info balloon".
>> 
>> Signed-off-by: Markus Armbruster <address@hidden>
>> ---
>>  balloon.c        | 2 +-
>>  hmp.c            | 2 +-
>>  qapi-schema.json | 4 ++--
>>  qapi/event.json  | 2 +-
>>  4 files changed, 5 insertions(+), 5 deletions(-)
>> 
>> diff --git a/balloon.c b/balloon.c
>> index 1d720ff..2ecca76 100644
>> --- a/balloon.c
>> +++ b/balloon.c
>> @@ -102,7 +102,7 @@ BalloonInfo *qmp_query_balloon(Error **errp)
>>      return info;
>>  }
>>  
>> -void qmp_balloon(int64_t target, Error **errp)
>> +void qmp_balloon(uint64_t target, Error **errp)
>>  {
>>      if (!have_balloon(errp)) {
>>          return;
>
> Can't you remove the:
>       if (target <= 0) {
>
> check?

Functional change when target == 0.  Impact is not clear to me.

> (The type of the trace_balloon_event probably needs fixing
> to be uint64_t rather than the unsigned long)

You're right.  I'll fix it.

>> diff --git a/hmp.c b/hmp.c
>> index 8257dd0..4556045 100644
>> --- a/hmp.c
>> +++ b/hmp.c
>> @@ -781,7 +781,7 @@ void hmp_info_balloon(Monitor *mon, const QDict *qdict)
>>          return;
>>      }
>>  
>> -    monitor_printf(mon, "balloon: actual=%" PRId64 "\n", info->actual >> 
>> 20);
>> +    monitor_printf(mon, "balloon: actual=%" PRIu64 "\n", info->actual >> 
>> 20);
>>  
>>      qapi_free_BalloonInfo(info);
>>  }
>> diff --git a/qapi-schema.json b/qapi-schema.json
>> index 3ad2bc0..23eb60d 100644
>> --- a/qapi-schema.json
>> +++ b/qapi-schema.json
>> @@ -2003,7 +2003,7 @@
>>  # Since: 0.14.0
>>  #
>>  ##
>> -{ 'struct': 'BalloonInfo', 'data': {'actual': 'int' } }
>> +{ 'struct': 'BalloonInfo', 'data': {'actual': 'size' } }
>>  
>>  ##
>>  # @query-balloon:
>> @@ -2603,7 +2603,7 @@
>>  # <- { "return": {} }
>>  #
>>  ##
>> -{ 'command': 'balloon', 'data': {'value': 'int'} }
>> +{ 'command': 'balloon', 'data': {'value': 'size'} }
>>  
>>  ##
>>  # @Abort:
>> diff --git a/qapi/event.json b/qapi/event.json
>> index 6d22b02..9dfc70b 100644
>> --- a/qapi/event.json
>> +++ b/qapi/event.json
>> @@ -488,7 +488,7 @@
>>  #
>>  ##
>>  { 'event': 'BALLOON_CHANGE',
>> -  'data': { 'actual': 'int' } }
>> +  'data': { 'actual': 'size' } }
>
> I was going to ask whether that was a problem for any external users,
> but there again libvirt looks like it reads it into an unsigned long
> long.

Yes.  See also my reply to Juan's review of PATCH 15.