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Wed, 26 Aug 2020 14:49:49 +0000 (GMT) Received: from b03ledav001.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AEEAC6E050; Wed, 26 Aug 2020 14:49:47 +0000 (GMT) Received: from cpe-172-100-175-116.stny.res.rr.com (unknown [9.85.170.64]) by b03ledav001.gho.boulder.ibm.com (Postfix) with ESMTP; Wed, 26 Aug 2020 14:49:47 +0000 (GMT) Subject: Re: [PATCH v10 01/16] s390/vfio-ap: add version vfio_ap module To: Cornelia Huck Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, freude@linux.ibm.com, borntraeger@de.ibm.com, mjrosato@linux.ibm.com, pasic@linux.ibm.com, alex.williamson@redhat.com, kwankhede@nvidia.com, fiuczy@linux.ibm.com, frankja@linux.ibm.com, david@redhat.com, imbrenda@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com References: <20200821195616.13554-1-akrowiak@linux.ibm.com> <20200821195616.13554-2-akrowiak@linux.ibm.com> <20200825120432.13a1b444.cohuck@redhat.com> From: Tony Krowiak Message-ID: Date: Wed, 26 Aug 2020 10:49:47 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200825120432.13a1b444.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-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-08-26_09:2020-08-26,2020-08-26 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 lowpriorityscore=0 phishscore=0 mlxlogscore=999 priorityscore=1501 bulkscore=0 impostorscore=0 clxscore=1015 adultscore=0 suspectscore=3 mlxscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008260110 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 8/25/20 6:04 AM, Cornelia Huck wrote: > On Fri, 21 Aug 2020 15:56:01 -0400 > Tony Krowiak wrote: > >> Let's set a version for the vfio_ap module so that automated regression >> tests can determine whether dynamic configuration tests can be run or >> not. >> >> Signed-off-by: Tony Krowiak >> --- >> drivers/s390/crypto/vfio_ap_drv.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c >> index be2520cc010b..f4ceb380dd61 100644 >> --- a/drivers/s390/crypto/vfio_ap_drv.c >> +++ b/drivers/s390/crypto/vfio_ap_drv.c >> @@ -17,10 +17,12 @@ >> >> #define VFIO_AP_ROOT_NAME "vfio_ap" >> #define VFIO_AP_DEV_NAME "matrix" >> +#define VFIO_AP_MODULE_VERSION "1.2.0" >> >> MODULE_AUTHOR("IBM Corporation"); >> MODULE_DESCRIPTION("VFIO AP device driver, Copyright IBM Corp. 2018"); >> MODULE_LICENSE("GPL v2"); >> +MODULE_VERSION(VFIO_AP_MODULE_VERSION); >> >> static struct ap_driver vfio_ap_drv; >> > Setting a version manually has some drawbacks: > - tools wanting to check for capabilities need to keep track which > versions support which features > - you need to remember to actually bump the version when adding a new, > visible feature > (- selective downstream backports may get into a pickle, but that's > arguably not your problem) > > Is there no way for a tool to figure out whether this is supported? > E.g., via existence of a sysfs file, or via a known error that will > occur. If not, it's maybe better to expose known capabilities via a > generic interface. This patch series introduces a new mediated device sysfs attribute, guest_matrix, so the automated tests could check for the existence of that interface. The problem I have with that is it will work for this version of the vfio_ap device driver - which may be all that is ever needed - but does not account for future enhancements which may need to be detected by tooling or automated tests. It seems to me that regardless of how a tool detects whether a feature is supported or not, it will have to keep track of that somehow. Can you provide more details about this generic interface of which you speak? >