[libvirt PATCH v4 1/3] add QEMU_CAPS_TCG_DISABLED and probe conditionally

[Michal Privoznik]

On 4/28/20 1:19 PM, Peter Krempa wrote:
> On Tue, Apr 28, 2020 at 13:13:32 +0200, Ján Tomko wrote:
>> On a Tuesday in 2020, Michal Privoznik wrote:
>>> On 4/27/20 10:22 PM, tobin wrote:
>>>
>>>> Yeah fine with me. Thank You.
>>>>
>>>> When it's a positive capability, you don't even need
>>>> virQEMUCapsProbeQMPTCGState,
>>>> you can just add the capability to virQEMUCapsObjectTypes.
>>>>
>>>
>>> Yep. I've went with that. This is now pushed.
>>>
>>
>> Umm, how do you know then if the capability is not missing because the
>> QEMU is too old to support it?
> 
> Yeah, when inverting it, the capability should be assumed by a version
> check (yuck) with old qemu.
> 

Yeah, the qemu commit in question is v2.10.0-rc0~93^2~18 and before that 
it wasn't possible to compile out TCG. And what do you mean "too old to 
support TCG"? Isn't TCG how QEMU started (with adaptation to KVM 
happening later)? The oldest mention of TCG that I bothered to find is 
in v0.14.0-rc0-936-g303d4e865b which is way older than current minimal 
1.5.0 so I think we are safe, aren't we? Or is there something that I am 
missing?

Michal