On 04.12.20 17:13, Dario Faggioli wrote:
> On Tue, 2020-12-01 at 10:18 +0100, Jürgen Groß wrote:
>> On 01.12.20 10:12, Jan Beulich wrote:
>>> What guarantees that you managed to find an unused ID, other
>>> than at current CPU speeds it taking too long to create 4
>>> billion pools? Since you're doing this under lock, wouldn't
>>> it help anyway to have a global helper variable pointing at
>>> the lowest pool followed by an unused ID?
>>
>> An admin doing that would be quite crazy and wouldn't deserve better.
>>
>> For being usable a cpupool needs to have a cpu assigned to it. And I
>> don't think we are coming even close to 4 billion supported cpus. :-)
>>
>> Yes, it would be possible to create 4 billion empty cpupools, but for
>> what purpose? There are simpler ways to make the system unusable with
>> dom0 root access.
>>
> Yes, I agree. I don't think it's worth going through too much effort
> for trying to deal with that.
> 
> What I'd do is:
>   - add a comment here, explaining quickly exactly this fact, i.e.,
>     that it's not that we've forgotten to deal with this and it's all
>     on purpose. Actually, it can be either a comment here or it can be
>     mentioned in the changelog. I'm fine either way
>   - if we're concerned about someone doing:
>       for i=1...N { xl cpupool-create foo bar }
>     with N ending up being some giant number, e.g., by mistake, I don't
>     think it's unreasonable to come up with an high enough (but
>     certainly not in the billions!) MAX_CPUPOOLS, and stop creating new
>     ones when we reach that level.

Do you agree that this could be another patch?

I'm not introducing that (theoretical) problem here.


Juergen