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Re: [Qemu-arm] [Qemu-devel] [PATCH v7 01/16] hw/cpu: introduce CPU clust

From: Luc Michel
Subject: Re: [Qemu-arm] [Qemu-devel] [PATCH v7 01/16] hw/cpu: introduce CPU clusters
Date: Mon, 3 Dec 2018 15:09:14 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.1

On 12/3/18 12:23 PM, Peter Maydell wrote:
> On Mon, 3 Dec 2018 at 11:21, Luc Michel <address@hidden> wrote:
>> On 11/30/18 5:52 PM, Peter Maydell wrote:
>>> Luc: what are the requirements on boards using CPU cluster
>>> objects? I assume these are both OK:
>>>  * does not use cluster objects at all
>>>    (the gdbstub puts all the CPUs in one process?)
>> Yes, when no clusters are found, a process with PID 1 is created and
>> used for all CPUs.
>>>  * all CPUs created are in some CPU cluster
>>>    (the gdbstub uses one process per CPU cluster)
>>> but what about
>>>  * some CPUs are created in a CPU cluster, but some
>>>    are "loose", not in any cluster at all> ?
>>> Is that just invalid, or do the "loose" CPUs end up in
>>> a default cluster (gdbstub process), or do they get
>>> one cluster each?
>> Currently this is valid and the "loose" CPUs end up in the first
>> available process (which will be PID 1 if we are in your first case,
>> i.e. no clusters in the machine).
> So if there are some defined clusters 1 and 2, and some
> loose CPUs, the clusters get PID 1 and PID 2, and the
> loose CPUs end up in PID 3? That seems reasonable.
No sorry I was not clear, the loose CPUs would end up on PID 1 in that case.

The current behaviour is as follows:
During gdb stub initialization:
  - A process is created per cluster.
  - If no cluster are found, an unique process is created with PID 1

When trying to find a CPU PID:
  - If it is attached to a cluster, return the associated process,
  - If it is loose, return the first available process.


> thanks
> -- PMM

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