Re: [Qemu-devel] [PATCH v2] New cpu-max field in query-machines QMP command output

[Michal Novotny <minovotn@redhat.com>]

On 04/09/2013 03:15 PM, Luiz Capitulino wrote:
> On Tue, 09 Apr 2013 15:09:21 +0200
> Michal Novotny <minovotn@redhat.com> wrote:
>
>> On 04/09/2013 03:06 PM, Luiz Capitulino wrote:
>>> On Mon, 08 Apr 2013 11:14:32 -0600
>>> Eric Blake <eblake@redhat.com> wrote:
>>>
>>>> On 04/08/2013 10:41 AM, Michal Novotny wrote:
>>>>> Alter the query-machines QMP command to output information about
>>>>> maximum number of CPUs for each machine type with default value
>>>>> set to 1 in case the number of max_cpus is not set.
>>>>>
>>>>> Signed-off-by: Michal Novotny <minovotn@redhat.com>
>>>>> ---
>>>>>  qapi-schema.json | 4 +++-
>>>>>  vl.c             | 1 +
>>>>>  2 files changed, 4 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/qapi-schema.json b/qapi-schema.json
>>>>> index db542f6..689ca8d 100644
>>>>> --- a/qapi-schema.json
>>>>> +++ b/qapi-schema.json
>>>>> @@ -2861,11 +2861,13 @@
>>>>>  #
>>>>>  # @default: #optional whether the machine is default
>>>>>  #
>>>>> +# @cpu-max: maximum number of CPUs supported by the machine type
>>>> Typically, when adding a field in a later version than the original
>>>> introduction of the datatype, we add '(since 1.5)' to make it obvious
>>>> when to expect the field.  However, as nothing (currently) enforces this
>>>> rule, I think such an addition is minor enough that it wouldn't
>>>> invalidate the use of my:
>>> Oh, it turns out I was making some confusion with this patch and
>>> didn't realize it was extending the query-machines command.
>>>
>>> I don't mean there's anything wrong with it, but my question is: doesn't
>>> this patch invalidates query-cpu-max?
>> Not really, the query-cpu-max shows maximum number of CPUs supported per
>> currently running machine (machine type) however the extension to
>> query-machines shows the maximum number of CPUs supported per each of
>> the displayed machine types. This usually doesn't matter on x86
>> architectures however it does matter on ARM, for example, as ARM has
>> some CPU models supporting up to 4 CPUs (highbank model) whereas most of
>> the ARM processors does have only one CPU.
> Can't we eliminate the query-cpu-max command if we extend the
> query-machines command to show which machine type is in use?

It may be useful as query-cpu-max is showing maximum number of CPUs
supported per machine type QEMU currently emulates. We don't have to
know the machine type and look for this number manually in the
query-machines output if we have query-cpu-max. We would have to both
know the machine type and look for the number manually to get max-cpu
count for currently running machine if we get rid of query-cpu-max command.

Whether something will use the value of CPU-max for currently running
machine (query-cpu-max output) is another question.

Michal

-- 
Michal Novotny <minovotn@redhat.com>, RHCE, Red Hat
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