From mboxrd@z Thu Jan 1 00:00:00 1970 From: Halil Pasic Subject: Re: [PATCH v9 12/22] s390: vfio-ap: sysfs interfaces to configure control domains Date: Mon, 27 Aug 2018 17:39:11 +0200 Message-ID: <5269782e-d0a9-9df0-b43f-eccfde00a223@linux.ibm.com> References: <1534196899-16987-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1534196899-16987-13-git-send-email-akrowiak@linux.vnet.ibm.com> <20180820162317.08bd7d23.cohuck@redhat.com> <660de00a-c403-28c1-4df4-82a973ab3ad5@linux.ibm.com> <20180821172548.57a6c758.cohuck@redhat.com> <82a391ee-85b1-cdc7-0f9b-d37fd8ba8e47@linux.ibm.com> <20180822114250.59a250aa.cohuck@redhat.com> <8bc5f207-f913-825c-f9fc-0a2c7fd280aa@linux.ibm.com> <219b352b-d5a2-189c-e205-82e7f9ae3d64@de.ibm.com> <9ef5fcb9-02e0-88e3-007c-eedb14e6db80@linux.ibm.com> <20180823122525.02fc4af3.cohuck@redhat.com> <20180827103316.4e7fbc10.cohuck@redhat.com> <65cb82b5-85ce-1831-5b2a-719d2cf27be8@linux.ibm.com> <20180827155126.440f2170.cohuck@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Christian Borntraeger , pmorel@linux.ibm.com, Tony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, freude@de.ibm.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, kwankhede@nvidia.com, bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com, alex.williamson@redhat.com, pmorel@linux.vnet.ibm.com, alifm@linux.vnet.ibm.com, mjrosato@linux.vnet.ibm.com, jjherne@linux.vnet.ibm.com, thuth@redhat.com, pasic@linux.vnet.ibm.com, berrange@redhat.com, fiuczy@linux.vnet.ibm.com, buendgen@de.ibm.com, frankja@linux.ibm.com To: Cornelia Huck , Tony Krowiak Return-path: In-Reply-To: <20180827155126.440f2170.cohuck@redhat.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 08/27/2018 03:51 PM, Cornelia Huck wrote: > On Mon, 27 Aug 2018 09:47:58 -0400 > Tony Krowiak wrote: > >> On 08/27/2018 04:33 AM, Cornelia Huck wrote: >>> On Thu, 23 Aug 2018 10:16:59 -0400 >>> Tony Krowiak wrote: >>> >>>> On 08/23/2018 06:25 AM, Cornelia Huck wrote: >>>>> On Wed, 22 Aug 2018 15:16:19 -0400 >>>>> Tony Krowiak wrote: >>>>> >>>>>> One of the things I suggested in a private conversation with Christian >>>>>> earlier >>>>>> today was to provide an additional rw sysfs attribute - a boolean - that >>>>>> indicates >>>>>> whether all usage domains should also be control domains. The default >>>>>> could be >>>>>> true. This would allow one to configure guests with usage-only domains >>>>>> as well >>>>>> as satisfy the convention. >>>>> Would this additional attribute then control "add usage domains to the >>>>> list of control domains automatically", or "don't allow to add a usage >>>>> domain if it has not already been added as a control domain"? >>>> It was just a proposal that wasn't really discussed at all, but this >>>> attribute would add usage domains to the list of control domains >>>> automatically if set to one. That would be the default behavior which >>>> would be turned off by manually setting it to zero. >>> If we want to do something like that, having it add the usage domains >>> automatically sounds like the more workable alternative. What I like >>> about this is that we make it explicit that we change the masks beyond >>> what the admin explicitly configured, and provide a knob to turn off >>> that behaviour. >> >> So, are you saying I should go ahead and implement this? > > I'm just saying that it does not sound like a bad idea :) > > If you agree that it's a good idea and if others also like it... I'd > certainly not mind you going ahead :) > I can live with it. What I don't like about it is that it adds more context dependent semantics. The same sequence of actions results in a different result (depending on the mode of operation). Regards, Halil