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Message-Id: <2e30976a-a2d0-c407-c491-acde565b63f1@linux.ibm.com>
Date: Mon, 9 Jul 2018 11:50:00 -0400
From: Halil Pasic <pasic@...ux.ibm.com>
To: pmorel@...ux.ibm.com, Tony Krowiak <akrowiak@...ux.vnet.ibm.com>,
linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org
Cc: freude@...ibm.com, schwidefsky@...ibm.com,
heiko.carstens@...ibm.com, borntraeger@...ibm.com,
cohuck@...hat.com, kwankhede@...dia.com,
bjsdjshi@...ux.vnet.ibm.com, pbonzini@...hat.com,
alex.williamson@...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,
Tony Krowiak <akrowiak@...ux.ibm.com>
Subject: Re: [PATCH v6 21/21] s390: doc: detailed specifications for AP
virtualization
On 07/09/2018 05:21 AM, Pierre Morel wrote:
> On 03/07/2018 01:10, Halil Pasic wrote:
>>
>>
>> On 06/29/2018 11:11 PM, Tony Krowiak wrote:
>>> This patch provides documentation describing the AP architecture and
>>> design concepts behind the virtualization of AP devices. It also
>>> includes an example of how to configure AP devices for exclusive
>>> use of KVM guests.
>>>
>>> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>>
>> I don't like the design of external interfaces except for:
>> * cpu model features, and
>> * reset handling.
>>
>> In particular:
>>
>>
> ...snip...
>
>> 4) If I were to act out the role of the administrator, I would prefer to think of
>> specifying or changing the access controls of a guest in respect to AP (that is
>> setting the AP matrix) as a single atomic operation -- which either succeeds or fails.
>>
>> The operation should succeed for any valid configuration, and fail for any invalid
>> on.
>>
>> The current piecemeal approach seems even less fitting if we consider changing the
>> access controls of a running guest. AFAIK changing access controls for a running
>> guest is possible, and I don't see a reason why should we artificially prohibit this.
>>
>> I think the current sysfs interface for manipulating the matrix is good for
>> manual playing around, but I would prefer having an interface that is better
>> suited for programs (e.g. ioctl).
>
> I disagree with using ioctl.
Why? What speaks against ioctl?
> I agree that the current implementation is not right.
> The configuration of APM and AQM should always be guarantied as coherent
> within the host but it can be done doing the right checks when using the sysfs.
>
I'm glad we agree on this one at least.
Regards,
Halil
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