From mboxrd@z Thu Jan 1 00:00:00 1970 From: Halil Pasic Subject: Re: [PATCH v6 21/21] s390: doc: detailed specifications for AP virtualization Date: Mon, 9 Jul 2018 11:50:00 -0400 Message-ID: <2e30976a-a2d0-c407-c491-acde565b63f1@linux.ibm.com> References: <1530306683-7270-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1530306683-7270-22-git-send-email-akrowiak@linux.vnet.ibm.com> <753c5e17-c241-580d-6e3a-a3c3159d44a8@linux.ibm.com> <0580735b-8813-f860-a2ac-654d82203b35@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <0580735b-8813-f860-a2ac-654d82203b35@linux.ibm.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: pmorel@linux.ibm.com, Tony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: freude@de.ibm.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, borntraeger@de.ibm.com, cohuck@redhat.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, Tony Krowiak List-ID: 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 >> >> 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