From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cornelia Huck Subject: Re: [RFC 05/19] s390/zcrypt: base implementation of AP matrix device driver Date: Thu, 16 Nov 2017 13:35:31 +0100 Message-ID: <20171116133531.1135a093.cohuck@redhat.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> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: Pierre Morel 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 List-ID: 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.]