Re: [Qemu-devel] [PATCH v2 4/7] scripts/qemu.py: set predefined machine type based on arch

[Cleber Rosa]

On 10/10/18 7:00 AM, Philippe Mathieu-Daudé wrote:
> On 10/10/2018 01:26, Cleber Rosa wrote:
>> Some targets require a machine type to be set, as there's no default
>> (aarch64 is one example).  To give a consistent interface to users of
>> this API, this changes set_machine() so that a predefined default can
>> be used, if one is not given.  The approach used is exactly the same
>> with the console device type.
>>
>> Also, even when there's a default machine type, for some purposes,
>> testing included, it's better if outside code is explicit about the
>> machine type, instead of relying on whatever is set internally.
>>
>> Signed-off-by: Cleber Rosa <address@hidden>
>> ---
>>  scripts/qemu.py | 22 +++++++++++++++++++++-
>>  1 file changed, 21 insertions(+), 1 deletion(-)
>>
>> diff --git a/scripts/qemu.py b/scripts/qemu.py
>> index d9e24a0c1a..fca9b76990 100644
>> --- a/scripts/qemu.py
>> +++ b/scripts/qemu.py
>> @@ -36,6 +36,15 @@ CONSOLE_DEV_TYPES = {
>>      r'^s390-ccw-virtio.*': 'sclpconsole',
>>      }
>>  
>> +#: Maps archictures to the preferred machine type
>> +MACHINE_TYPES = {
>> +    r'^aarch64$': 'virt',
>> +    r'^ppc$': 'g3beige',
>> +    r'^ppc64$': 'pseries',
>> +    r'^s390x$': 's390-ccw-virtio',
>> +    r'^x86_64$': 'q35',
> 
> Why choose Q35 rather than PC (the default)?
> 
> I was wondering about how to generate variants/machines.json but this is
> definitively something we want to do via a QMP query.
> 
> Eduardo what do you think?
> 

It was motivated by Eduardo's initiative to make q35 the default "across
the board".  He can confirm and give more details.

- Cleber.

>> +    }
>> +
>>  
>>  class QEMUMachineError(Exception):
>>      """
>> @@ -413,13 +422,24 @@ class QEMUMachine(object):
>>          """
>>          self._arch = arch
>>  
>> -    def set_machine(self, machine_type):
>> +    def set_machine(self, machine_type=None):
>>          '''
>>          Sets the machine type
>>  
>>          If set, the machine type will be added to the base arguments
>>          of the resulting QEMU command line.
>>          '''
>> +        if machine_type is None:
>> +            if self._arch is None:
>> +                raise QEMUMachineError("Can not set a default machine type: 
>> "
>> +                                       "QEMU instance without a defined 
>> arch")
>> +            for regex, machine in MACHINE_TYPES.items():
>> +                if re.match(regex, self._arch):
>> +                    machine_type = machine
>> +                    break
>> +            if machine_type is None:
>> +                raise QEMUMachineError("Can not set a machine type: no "
>> +                                       "matching machine type definition")
>>          self._machine = machine_type
>>  
>>      def set_console(self, device_type=None):
>>