From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933899AbdKPOZm (ORCPT ); Thu, 16 Nov 2017 09:25:42 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:57480 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933633AbdKPOZi (ORCPT ); Thu, 16 Nov 2017 09:25:38 -0500 Subject: Re: [RFC 05/19] s390/zcrypt: base implementation of AP matrix device driver To: Cornelia Huck Cc: 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, borntraeger@de.ibm.com, kwankhede@nvidia.com, bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com, alex.williamson@redhat.com, alifm@linux.vnet.ibm.com, mjrosato@linux.vnet.ibm.com, qemu-s390x@nongnu.org, jjherne@linux.vnet.ibm.com, thuth@redhat.com, pasic@linux.vnet.ibm.com References: <1507916344-3896-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1507916344-3896-6-git-send-email-akrowiak@linux.vnet.ibm.com> <20171114134040.3fcd6efd.cohuck@redhat.com> <06ddee4e-e1b8-ba17-5e3e-241e4dcf7cd0@linux.vnet.ibm.com> <20171116133531.1135a093.cohuck@redhat.com> From: Pierre Morel Date: Thu, 16 Nov 2017 15:25:28 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <20171116133531.1135a093.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 17111614-0020-0000-0000-000003CD1510 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17111614-0021-0000-0000-000042624F36 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-11-16_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1711160197 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/11/2017 13:35, Cornelia Huck wrote: > On Thu, 16 Nov 2017 13:02:26 +0100 > Pierre Morel wrote: > >> On 14/11/2017 17:37, Tony Krowiak wrote: >>> On 11/14/2017 07:40 AM, Cornelia Huck wrote: >>>> On Fri, 13 Oct 2017 13:38:50 -0400 >>>> Tony Krowiak wrote: > >>>>> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig >>>>> index 48af970..411c19a 100644 >>>>> --- a/arch/s390/Kconfig >>>>> +++ b/arch/s390/Kconfig >>>>> @@ -722,6 +722,19 @@ config VFIO_CCW >>>>>         To compile this driver as a module, choose M here: the >>>>>         module will be called vfio_ccw. >>>>> +config VFIO_AP_MATRIX >>>>> +    def_tristate m >>>>> +    prompt "Support for Adjunct Processor Matrix device interface" >>>>> +    depends on ZCRYPT >>>>> +    select VFIO >>>>> +    select MDEV >>>>> +    select VFIO_MDEV >>>>> +    select VFIO_MDEV_DEVICE >>>>> +    select IOMMU_API >>>> I think the more common pattern is to depend on the VFIO configs >>>> instead of selecting them. >>> It's ironic because I originally changed from using 'depends on' and >>> changed it based on review comments made >>> on our internal mailing list. I'll go with 'depends on'. >> >> Is doing like the others a sufficient good reason? >> What if the first who did this did not really think about it? >> >> When an administrator configure the kernel what does he think? >> >> - I want to have AP through AP_VFIO in my guests >> and he get implicitly VFIO >> or >> - I want to have VFIO >> and he has to explicitly add AP_VFIO too >> >> It seems to me that the first is much more user friendly. >> >> Please tell me if I missed something. dependencies? collateral damages? >> my logic is wrong? > > Using select for anything that's not a simple infrastructure dependency > may lead into trouble (we've had issues in the past where options tried > to enable other options but missed dependencies). Understood, using dependencies is safer against a third party introducing a bug that would add a dependency to a member of the list but not update our list of selections. > > If a user wants to use vfio-ap, I think it is reasonable to expect them > to figure out that they need both ap and vfio for that. > > [And config help has gotten much better than it was years ago; it's not > that hard to figure out what is actually needed.] > OK for Darwin selection for admins, (a gentle Darwin :) I acknowledge) and on our side we spare to us running after our disappeared AP VFIO. Regards, Pierre -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany