From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Krowiak Subject: Re: [RFC 05/19] s390/zcrypt: base implementation of AP matrix device driver Date: Tue, 14 Nov 2017 13:15:27 -0500 Message-ID: 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> <20171114180036.262eff80.cohuck@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20171114180036.262eff80.cohuck@redhat.com> Content-Language: en-US Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: Cornelia Huck 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, pmorel@linux.vnet.ibm.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 11/14/2017 12:00 PM, Cornelia Huck wrote: > On Tue, 14 Nov 2017 11:37:05 -0500 > 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/drivers/s390/crypto/ap_matrix_bus.c b/drivers/s390/crypto/ap_matrix_bus.c >>>> index 4eb1e3c..66bfa54 100644 >>>> --- a/drivers/s390/crypto/ap_matrix_bus.c >>>> +++ b/drivers/s390/crypto/ap_matrix_bus.c >>>> @@ -75,10 +75,18 @@ static int ap_matrix_dev_create(void) >>>> return 0; >>>> } >>>> >>>> +struct ap_matrix *ap_matrix_get_device(void) >>>> +{ >>>> + return matrix; >>> See the comments I had for the previous patch. In particular, I think >>> it is better to retrieve a pointer to the matrix device via driver core >>> methods. >> I got some objections to creating a new bus and since there will only ever >> be a single AP matrix device, I decided there really wasn't a need for an >> AP matrix bus and got rid of it. I opted instead to create the matrix >> device >> in the init function of the vfio_ap_matrix driver. Rather than passing >> around a >> pointer, I put the following in vfio_ap_matrix_private.h: >> >> struct ap_matrix { >> struct device device; >> spinlock_t qlock; >> struct list_head queues; >> }; >> >> extern struct ap_matrix ap_matrix; >> >> ... and declared the ap_matrix in the driver (vfio_ap_matrix_drv.c) >> file as: >> >> struct ap_matrix ap_matrix; >> >> Does this seem like a reasonable approach? > Getting rid of the bus as overhead is not unreasonable. > > I'm feeling a bit queasy about the extern, however. I'd prefer a getter > function (that also makes sure refcounting rules are followed). I now think I can avoid having to reference the ap_matrix device from multiple places. The reason the device is referenced in vfio_ap_matrix_ops.c is because there is a need for information about the AP queues that have been bound to the vfio_ap_matrix device driver. If interfaces are provided by the vfio_ap_matrix device driver to access the needed information, it won't be necessary to reference the ap_matrix device directly in vfio_ap_matrix_ops. I think this would be a better solution, don't you? > > We can't get around referencing this device from multiple files, can we? The only way would be to roll up vfio_ap_matrix_ops.c into vfio_ap_matrix_drv.c. I followed the pattern established by the vfio_ccw >