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Thu, 17 Sep 2020 13:54:08 GMT Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C664BAE05F; Thu, 17 Sep 2020 13:54:08 +0000 (GMT) Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 004FCAE05C; Thu, 17 Sep 2020 13:54:07 +0000 (GMT) Received: from localhost.localdomain (unknown [9.85.128.188]) by b01ledav005.gho.pok.ibm.com (Postfix) with ESMTP; Thu, 17 Sep 2020 13:54:07 +0000 (GMT) Subject: Re: [PATCH v10 04/16] s390/zcrypt: driver callback to indicate resource in use 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, kernel test robot References: <20200821195616.13554-1-akrowiak@linux.ibm.com> <20200821195616.13554-5-akrowiak@linux.ibm.com> <20200914172947.533ddf56.cohuck@redhat.com> <20200917141442.6e531799.cohuck@redhat.com> From: Tony Krowiak Message-ID: Date: Thu, 17 Sep 2020 09:54:07 -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: <20200917141442.6e531799.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=2020-09-17_09:2020-09-16,2020-09-17 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 mlxscore=0 suspectscore=2 bulkscore=0 mlxlogscore=999 priorityscore=1501 lowpriorityscore=0 malwarescore=0 impostorscore=0 spamscore=0 clxscore=1015 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009170104 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 9/17/20 8:14 AM, Cornelia Huck wrote: > On Tue, 15 Sep 2020 15:32:35 -0400 > Tony Krowiak wrote: > >> On 9/14/20 11:29 AM, Cornelia Huck wrote: >>> On Fri, 21 Aug 2020 15:56:04 -0400 >>> Tony Krowiak wrote: >>> >>>> Introduces a new driver callback to prevent a root user from unbinding >>>> an AP queue from its device driver if the queue is in use. The intent of >>>> this callback is to provide a driver with the means to prevent a root user >>>> from inadvertently taking a queue away from a matrix mdev and giving it to >>>> the host while it is assigned to the matrix mdev. The callback will >>>> be invoked whenever a change to the AP bus's sysfs apmask or aqmask >>>> attributes would result in one or more AP queues being removed from its >>>> driver. If the callback responds in the affirmative for any driver >>>> queried, the change to the apmask or aqmask will be rejected with a device >>>> in use error. >>>> >>>> For this patch, only non-default drivers will be queried. Currently, >>>> there is only one non-default driver, the vfio_ap device driver. The >>>> vfio_ap device driver facilitates pass-through of an AP queue to a >>>> guest. The idea here is that a guest may be administered by a different >>>> sysadmin than the host and we don't want AP resources to unexpectedly >>>> disappear from a guest's AP configuration (i.e., adapters, domains and >>>> control domains assigned to the matrix mdev). This will enforce the proper >>>> procedure for removing AP resources intended for guest usage which is to >>>> first unassign them from the matrix mdev, then unbind them from the >>>> vfio_ap device driver. >>>> >>>> Signed-off-by: Tony Krowiak >>>> Reported-by: kernel test robot >>> This looks a bit odd... >> I've removed all of those. These kernel test robot errors were flagged >> in the last series. The review comments from the robot suggested >> the reported-by, but I assume that was for patches intended to >> fix those errors, so I am removing these as per Christian's comments. > Yes, I think the Reported-by: mostly makes sense if you include a patch > to fix something on top. > >>> >>>> --- >>>> drivers/s390/crypto/ap_bus.c | 148 ++++++++++++++++++++++++++++++++--- >>>> drivers/s390/crypto/ap_bus.h | 4 + >>>> 2 files changed, 142 insertions(+), 10 deletions(-) >>>> >>> (...) >>> >>>> @@ -1107,12 +1118,70 @@ static ssize_t apmask_show(struct bus_type *bus, char *buf) >>>> return rc; >>>> } >>>> >>>> +static int __verify_card_reservations(struct device_driver *drv, void *data) >>>> +{ >>>> + int rc = 0; >>>> + struct ap_driver *ap_drv = to_ap_drv(drv); >>>> + unsigned long *newapm = (unsigned long *)data; >>>> + >>>> + /* >>>> + * No need to verify whether the driver is using the queues if it is the >>>> + * default driver. >>>> + */ >>>> + if (ap_drv->flags & AP_DRIVER_FLAG_DEFAULT) >>>> + return 0; >>>> + >>>> + /* The non-default driver's module must be loaded */ >>>> + if (!try_module_get(drv->owner)) >>>> + return 0; >>>> + >>>> + if (ap_drv->in_use) >>>> + if (ap_drv->in_use(newapm, ap_perms.aqm)) >>>> + rc = -EADDRINUSE; >>> ISTR that Christian suggested -EBUSY in a past revision of this series? >>> I think that would be more appropriate. >> I went back and looked and sure enough, he did recommend that. >> You have a great memory! I didn't respond to that comment, so I >> must have missed it at the time. >> >> I personally prefer EADDRINUSE because I think it is more indicative >> of the reason an AP resource can not be assigned back to the host >> drivers is because it is in use by a guest or, at the very least, reserved >> for use by a guest (i.e., assigned to an mdev). To say it is busy implies >> that the device is busy performing encryption services which may or >> may not be true at a given moment. Even if so, that is not the reason >> for refusing to allow reassignment of the device. > I have a different understanding of these error codes: EADDRINUSE is > something used in the networking context when an actual address is > already used elsewhere. EBUSY is more of a generic error that indicates > that a certain resource is not free to perform the requested operation; > it does not necessarily mean that the resource is currently actively > doing something. Kind of when you get EBUSY when trying to eject > something another program holds a reference on: that other program > might not actually be doing anything, but it potentially could. I'll go ahead and change it to -EBUSY. >