Re: [Qemu-devel] [RFC PATCH 0/8] removal of tci (tcg interpreter)

[Thomas Huth]

On 29.06.2017 18:07, Daniel P. Berrange wrote:
> On Thu, Jun 29, 2017 at 05:46:26PM +0200, Thomas Huth wrote:
>> On 29.06.2017 17:06, Paolo Bonzini wrote:
>>>
>>>
>>> On 29/06/2017 10:46, Thomas Huth wrote:
>>>>> Patches 7,8 are the removal, marked RFC... let's debate!
>>>> ... but NACK for a direct removal. Common sense is to make obsolete
>>>> features as deprecated first and then wait for 2 public releases before
>>>> the final removal, so that users still have a chance to speak up in case
>>>> they still need the feature and are willing to maintain it.
>>>
>>> I think this is a slightly different case than what is in
>>> http://wiki.qemu.org/Features/LegacyRemoval.
>>>
>>> TCI is enabled only with a specific configure argument if your machine
>>> is not supported by TCG.  This would break _build_ configurations, not
>>> user configurations.  It's a remote possibility that users are building
>>> their own QEMU, with TCI enabled, to work around a TCG bug.  So we can
>>> be more speedy in removing the code.
>>
>> You never know ... it's unlikely, but there might be people around who
>> run configure with "--enable-tcg-interpreter" on purpose. And why the
>> hurry for removing this? It's been around in the current shape since
>> years, so waiting for two more releases does not hurt, does it?
> 
> The flipside is that even if we delete it, if someone does suddenly
> care, the code is still there in git & easy to undelete again. Given
> that we believe there are zero users, it is known broken in many
> ways, and TCG provides a working alternative, I don't see a strong
> reason to not just kill it right away. 

At least I was using TCI a couple of times during the last years (when I
was suspecting a bug in the normal TCG backend, so I could compare).
There might be other people, too, so I would not dare to say that there
are zero users!
Though I used it a couple of times in the past, I personally would not
object the removal of TCI nowadays since the normal TCG backends have
become pretty mature ... but other users of TCI might have a different
opinion here, so let's mark it as deprecated now and remove it next year
(unless somebody speaks up and explains why it should not be removed).

 Thomas