linux-kernel - Re: [Qemu-devel] [RFC PATCH v2 04/15] cpu-model/s390: Introduce S390 CPU models

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Date:	Fri, 20 Feb 2015 20:55:11 +0100
From:	Alexander Graf <agraf@...e.de>
To:	Michael Mueller <mimu@...ux.vnet.ibm.com>
CC:	"qemu-devel@...gnu.org" <qemu-devel@...gnu.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Gleb Natapov <gleb@...nel.org>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	"Jason J. Herne" <jjherne@...ux.vnet.ibm.com>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Andreas Faerber <afaerber@...e.de>,
	Richard Henderson <rth@...ddle.net>
Subject: Re: [Qemu-devel] [RFC PATCH v2 04/15] cpu-model/s390: Introduce S390
 CPU models



On 20.02.15 20:43, Michael Mueller wrote:
> On Fri, 20 Feb 2015 18:50:20 +0100
> Alexander Graf <agraf@...e.de> wrote:
> 
>>
>>
>>
>>> Am 20.02.2015 um 18:37 schrieb Michael Mueller <mimu@...ux.vnet.ibm.com>:
>>>
>>> On Fri, 20 Feb 2015 17:57:52 +0100
>>> Alexander Graf <agraf@...e.de> wrote:
>>>
>>>> Because all CPUs we have in our list only expose 128 bits?
>>>
>>> Here a STFLE result on a EC12 GA2, already more than 128 bits... Is that model on the list?
>>
>> If that model has 3 elements, yes, the array should span 3.
>>
>> I hope it's in the list. Every model wecare about should be, no?
>>
> 
> On my list? Yes!
> 
>>>
>>> [mimu@...lp59 s390xfac]$ ./s390xfac -b
>>> fac[0] = 0xfbfffffbfcfff840
>>> fac[1] = 0xffde000000000000
>>> fac[2] = 0x1800000000000000
>>>>
>>>>> I want to have this independent from a future machine of the z/Arch. The kernel stores the
>>>>> full facility set, KVM does and there is no good reason for QEMU not to do. If other
>>>>> accelerators decide to just implement 64 or 128 bits of facilities that's ok...  
>>>>
>>>> So you want to support CPUs that are not part of the list?
>>>
>>> The architecture at least defines more than 2 or 3. Do you want me to limit it to an arbitrary
>>> size?. Only in QEMU or also in the KVM interface?
>>
>> Only internally in QEMU. The kvm interface should definitely be as big as the spec allows!
> 
> Right, now we're on the same page again. That can be taken in consideration. ... Although it's
> just and optimization. :-)

Yeah. You could also consider using the QEMU built-in bitmap type and
functions and just convert from there. That would give you native
support for bit values > 64.


Alex
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