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Re: [PATCH v3 4/6] xen/cpupool: Create different cpupools at boot time
- To: Julien Grall <julien@xxxxxxx>
- From: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
- Date: Tue, 22 Mar 2022 08:35:08 +0000
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- Cc: Luca Fancellu <Luca.Fancellu@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Wei Chen <Wei.Chen@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Wei Liu <wl@xxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Dario Faggioli <dfaggioli@xxxxxxxx>
- Delivery-date: Tue, 22 Mar 2022 08:35:29 +0000
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- Thread-topic: [PATCH v3 4/6] xen/cpupool: Create different cpupools at boot time
Hi Julien,
> On 21 Mar 2022, at 18:44, Julien Grall <julien@xxxxxxx> wrote:
>
> Hi Bertrand,
>
> On 21/03/2022 17:19, Bertrand Marquis wrote:
>>> On 21 Mar 2022, at 17:36, Julien Grall <julien@xxxxxxx> 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
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