From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934296AbdKPOZv (ORCPT ); Thu, 16 Nov 2017 09:25:51 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:49524 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933953AbdKPOZn (ORCPT ); Thu, 16 Nov 2017 09:25:43 -0500 Subject: Re: [RFC 05/19] s390/zcrypt: base implementation of AP matrix device driver To: Cornelia Huck , Pierre Morel Cc: 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: Tony Krowiak Date: Thu, 16 Nov 2017 09:25:27 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20171116133531.1135a093.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 17111614-0016-0000-0000-000007D1270F X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008073; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000240; SDB=6.00946724; UDB=6.00477910; IPR=6.00727016; BA=6.00005694; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00018044; XFM=3.00000015; UTC=2017-11-16 14:25:33 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17111614-0017-0000-0000-00003C46808A 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=1011 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 11/16/2017 07:35 AM, 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). > > 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.] Is it sufficient to specify 'depends on ZCRYPT && VFIO_MDEV_DEVICE' since 'VFIO_MDEV_DEVICE depends on VFIO && VFIO_MDEV' and 'VFIO_MDEV depends on VFIO' and 'VFIO depends on IOMMU_API'? >