Re: [PATCH v3 4/6] xen/cpupool: Create different cpupools at boot time

[Bertrand Marquis <Bertrand.Marquis@arm.com>]

Hi Julien,

> On 21 Mar 2022, at 18:44, Julien Grall <julien@xen.org> wrote:
> 
> Hi Bertrand,
> 
> On 21/03/2022 17:19, Bertrand Marquis wrote:
>>> On 21 Mar 2022, at 17:36, Julien Grall <julien@xen.org> wrote:
>>>> So I don’t know why on x86 we must have cpu0 in cpupool0, maybe x86 maintainer have more knowledge about that and
>>>> I can put a comment here.
>>> 
>>> On Arm, we are not yet supporting all the CPU features that x86 supports (e.g. CPU hotplug, suspend/resume...). So I a am bit concerned that the restriction is just not there yet (or possibly hidden).
>>> 
>>> Therefore, before lifting the restriction on Arm (and other arch), I would like us to understand why it is necessary on x86.
>>> 
>>> We may not have the answer quickly, so is it going to be a problem to keep the restriction on Arm?
>> I am ok to keep the limitation to have dom0 always running on cpu0.
>> Only limitation I can see is that on a big little system, dom0 needs to stay on the type of core of the first booted core.
> 
> Where does this limitation come from?

If dom0 must run on core0 and core0 is Little then you cannot build a system where dom0 is running on big cores.
If the limitation is not there, you can build such a configuration without any dependency to the boot core type.

Cheers
Bertrand

> 
> Cheers,
> 
> -- 
> Julien Grall