linux-kernel - Re: [PATCH v11 26/26] s390: doc: detailed specifications for AP virtualization

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Date:   Thu, 27 Sep 2018 09:12:39 -0400
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Christian Borntraeger <borntraeger@...ibm.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Halil Pasic <pasic@...ux.ibm.com>
Cc:     Alex Williamson <alex.williamson@...hat.com>,
        Tony Krowiak <akrowiak@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, kwankhede@...dia.com,
        bjsdjshi@...ux.vnet.ibm.com, pbonzini@...hat.com,
        pmorel@...ux.vnet.ibm.com, alifm@...ux.vnet.ibm.com,
        mjrosato@...ux.vnet.ibm.com, jjherne@...ux.vnet.ibm.com,
        thuth@...hat.com, pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com,
        frankja@...ux.ibm.com
Subject: Re: [PATCH v11 26/26] s390: doc: detailed specifications for AP
 virtualization

On 09/27/2018 07:59 AM, Christian Borntraeger wrote:
> 
> 
> On 09/27/2018 01:51 PM, Cornelia Huck wrote:
>> On Thu, 27 Sep 2018 13:29:43 +0200
>> Halil Pasic <pasic@...ux.ibm.com> wrote:
>>
>>> On 09/27/2018 12:42 AM, Alex Williamson wrote:
>>>> On Tue, 25 Sep 2018 19:16:41 -0400
>>>> Tony Krowiak <akrowiak@...ux.vnet.ibm.com> wrote:
>>>>> +   This is how the matrix is configured for Guest2:
>>>>> +
>>>>> +      echo 5 > assign_adapter
>>>>> +      echo 0x47 > assign_domain
>>>>> +      echo 0xff > assign_domain
>>>>> +
>>>>> +   This is how the matrix is configured for Guest3:
>>>>> +
>>>>> +      echo 6 > assign_adapter
>>>>> +      echo 0x47 > assign_domain
>>>>> +      echo 0xff > assign_domain
>>>>> +
>>>>
>>>> I'm curious why this interface didn't adopt the +/- notation invented
>>>> above for consistency.  Too difficult to do rollbacks with a string on
>>>> entries?
>>>>    
>>>
>>> I remember that we did discuss that possibility around v9, but I can't
>>> tell why did we decide to not implement it. Maybe Tony has an answer.
>>
>> IIRC, that was a discussion on the base ap driver interfaces rather
>> than vfio-ap.
>>
>>>
>>> Anyway, if we were to do that, we would use different attribute names
>>> (e.g. just domain_mask, or something similar instead of
>>> (assign|unassign)_xxx). So I think such an interface can still be added
>>> on top of the existing one. Having that said having multiple interfaces
>>> for the very same thing is usually not so nice IMHO.
>>
>> Nod to all of your points.
>>
>> As we do the configuration while the guest is not running anyway, the
>> different interfaces probably do not make that much difference in
>> practice. It should be fine to stick to the current interface for now
>> and only add a new one if we really think it is significantly better.
> 
> Tony, can you maybe provide a quick on-top patch that clarifies Alex
> comments regarding the documentation? (State that is is big endian,
> fixup the small things etc).
> I can then either fold it in or provide it as an on top patch depending
> on how much has changed.

Will do.

>