Re: [PATCH 05/22] hw/arm: Select VIRTIO_NET for virt machine

["Alex Bennée" <alex.bennee@linaro.org>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 5/9/23 12:00, Peter Maydell wrote:
>> On Tue, 9 May 2023 at 10:42, Paolo Bonzini <pbonzini@redhat.com> wrote:
>>>
>>> On 5/9/23 11:27, Peter Maydell wrote:
>>>> On Mon, 8 May 2023 at 23:24, Paolo Bonzini <pbonzini@redhat.com> wrote:
>>>>> --without-default-devices is not about choosing to not build
>>>>> some devices; it is about making non-selected devices opt-in
>>>>> rather than opt-out.
>>>>
>>>> Hmm, so it's basically "the person doing the configuration needs
>>>> to know what they're doing, the Kconfig system will give them
>>>> no hints about what devices might or might not be needed to
>>>> make machine type M functional" ?
>>>
>>> It depends on what you mean by functional.  I would say you do get what
>>> is needed to have a functional machine, but not what is needed to have a
>>> useful machine.
>> If you need to pass '-nodefaults' to get the thing to start up at
>> all, that seems to be stretching the definition of "functional"
>> to me.
>
> Then, an accurate description that uses "functional" in that sense
> could be as follows:
>
> The Kconfig system will include any devices and subsystems that are
> mandatory for a given machine type, and will flag any configuration
> conflicts. However, the person doing the configuration still needs to
> know which devices are needed (on top of the mandatory ones) to obtain
> a functional guest, and Kconfig will not provide any hints in this
> respect.

So I thought that was the model I was following in adding devices but it
seems I don't understand the no-defaults behaviour. What is the
difference between a device that is added in the machine.c that makes it
required or expendable with -nodefaults?

>
> Paolo


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro