Re: [Qemu-devel] [PATCH 01/15] configure: add the disable-tcg option

[Thomas Huth]

On 22.06.2017 11:26, Paolo Bonzini wrote:
> 
> 
> On 22/06/2017 08:33, Thomas Huth wrote:
>> On 22.06.2017 08:22, Paolo Bonzini wrote:
>>>
>>>> On 21.06.2017 12:19, Yang Zhong wrote:
>>>>> Add the disable-tcg option into configure and echo CONFIG_TCG=y into
>>>>> $config_target_mak. The default tcg is enabled for all build. If tcg
>>>>> is disabled in the build, only i386|x86_64 softmmu option can be disabled,
>>>>> other softmmu of tagets and users build defaultly enabled the tcg.
>>>> Why do you want to limit this disablement to x86 only? There are also
>>>> other architectures that support KVM (ARM, PPC, MIPS), so disabling TCG
>>>> might be possible there, too. So I think it might be better to check
>>>> whether KVM is possible instead.
>>>
>>> You need to be careful and not use any helper from e.g. KVM or migration
>>> code.  So I would be very surprised if any other architecture compiles
>>> with --disable-tcg.
>>
>> OK, fair, but we finally might want to get there, so I think we should
>> allow the parameter in the configure script for other architectures,
>> too, and then fix the bugs once we can try it out.
> 
> I think it's the other way round---when someone wants to fix it, they
> should add their architecture to the list of targets that support
> --disable-tcg.  "./configure <anything>", as a goal, should fail
> immediately if make won't succeed; compilation errors are always a worse
> experience.

Fine for me, too, but then the configure script should exit with a
proper error message when the user tried to specify --disable-tcg on a
non-x86 architecture. If I get the current patch right, it silently
falls back to CONFIG_TCG=y instead, which is IMHO also a bad experience.

 Thomas