Re: [Qemu-devel] [RFC PATCH v0 0/9] Generic cpu-core device

From: "Andreas Färber" <afaerber@suse.de>
To: Zhu Guihua <zhugh.fnst@cn.fujitsu.com>,
	bharata@linux.vnet.ibm.com, Igor Mammedov <imammedo@redhat.com>
Cc: mjrosato@linux.vnet.ibm.com, peter.maydell@linaro.org,
	ehabkost@redhat.com, qemu-devel@nongnu.org, agraf@suse.de,
	borntraeger@de.ibm.com, pbonzini@redhat.com,
	izumi.taku@jp.fujitsu.com, david@gibson.dropbear.id.au
Subject: Re: [Qemu-devel] [RFC PATCH v0 0/9] Generic cpu-core device
Date: Wed, 16 Dec 2015 16:16:58 +0100	[thread overview]
Message-ID: <5671806A.5040002@suse.de> (raw)
In-Reply-To: <566FA4BF.6080709@cn.fujitsu.com>

Am 15.12.2015 um 06:27 schrieb Zhu Guihua:
> <snip>
>>> and allow individual targets to use its own way to build CPUs?
>>>
>>> For initial conversion of x86-cpus to device-add we could do pretty
>>> much the same like we do now, where cpu devices will appear under:
>>> /machine (pc-i440fx-2.5-machine)
>>>    /unattached (container)
>>>      /device[x] (qemu64-x86_64-cpu)
>>>
>>> since we don't have to maintain/model dummy socket/core objects.
>>>
>>> PowerPC could do the similar only at core level since it has
>>> need for modeling core objects.
>>>
>>> It doesn't change anything wrt current introspection state, since
>>> cpus could be still found by mgmt tools that parse QOM tree.
>>>
>>> We probably should split 2 conflicting goals we are trying to meet here,
>>>
>>>   1. make device-add/dell work with cpus /
>>>       drop support for cpu-add in favor of device_add
>>>
>>>   2. how to model QOM tree view for CPUs in arch independent manner
>>>      to make mgmt layer life easier.
>>>
>>> and work on them independently instead of arguing for years,
>>> that would allow us to make progress in #1 while still thinking about
>>> how to do #2 the right way if we really need it.
>> Makes sense, s390 developer also recommends the same. Given that we have
>> CPU hotplug patchsets from x86, PowerPC and s390 all implementing
>> device_add
>> semantics pending on the list, can we hope to get them merged for
>> QEMU-2.6 ?
>>
>> So as seen below, the device is either "cpu_model-cpu_type" or just
>> "cpu_type".
>>
>> -device POWER8-powerpc64-cpu (pseries)
>> -device qemu64-x86_64-cpu (pc)
>> -device s390-cpu (s390)
>>
>> Is this going to be the final acceptable semantics ? Would libvirt be
>> able
>> to work with this different CPU device names for different guests ?
> 
> Is operating on core level not final decision ?

No, it is absolutely _not_ the conclusion from Seattle.

Andreas

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