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Wed, 6 Jan 2021 15:16:27 +0000 (GMT) Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 50DFCC6055; Wed, 6 Jan 2021 15:16:25 +0000 (GMT) Received: from cpe-66-24-58-13.stny.res.rr.com (unknown [9.85.193.150]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTP; Wed, 6 Jan 2021 15:16:25 +0000 (GMT) Subject: Re: [PATCH v13 00/15] s390/vfio-ap: dynamic configuration support To: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: freude@linux.ibm.com, borntraeger@de.ibm.com, cohuck@redhat.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, hca@linux.ibm.com, gor@linux.ibm.com References: <20201223011606.5265-1-akrowiak@linux.ibm.com> From: Tony Krowiak Message-ID: <3c350e32-3206-25cb-1b1e-6577e8c15ae2@linux.ibm.com> Date: Wed, 6 Jan 2021 10:16:24 -0500 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: <20201223011606.5265-1-akrowiak@linux.ibm.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=2.50.10434:6.0.343,18.0.737 definitions=2021-01-06_06:2021-01-06,2021-01-06 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 spamscore=0 malwarescore=0 mlxscore=0 lowpriorityscore=0 priorityscore=1501 mlxlogscore=999 phishscore=0 adultscore=0 bulkscore=0 impostorscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101060091 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ping On 12/22/20 8:15 PM, Tony Krowiak wrote: > Note: Patch 1, s390/vfio-ap: clean up vfio_ap resources when KVM > pointer invalidated does not belong to this series. It has been > posted as a separate patch to fix a known problem. It is included > here because it will likely pre-req for this series. > > The current design for AP pass-through does not support making dynamic > changes to the AP matrix of a running guest resulting in a few > deficiencies this patch series is intended to mitigate: > > 1. Adapters, domains and control domains can not be added to or removed > from a running guest. In order to modify a guest's AP configuration, > the guest must be terminated; only then can AP resources be assigned > to or unassigned from the guest's matrix mdev. The new AP > configuration becomes available to the guest when it is subsequently > restarted. > > 2. The AP bus's /sys/bus/ap/apmask and /sys/bus/ap/aqmask interfaces can > be modified by a root user without any restrictions. A change to > either mask can result in AP queue devices being unbound from the > vfio_ap device driver and bound to a zcrypt device driver even if a > guest is using the queues, thus giving the host access to the guest's > private crypto data and vice versa. > > 3. The APQNs derived from the Cartesian product of the APIDs of the > adapters and APQIs of the domains assigned to a matrix mdev must > reference an AP queue device bound to the vfio_ap device driver. The > AP architecture allows assignment of AP resources that are not > available to the system, so this artificial restriction is not > compliant with the architecture. > > 4. The AP configuration profile can be dynamically changed for the linux > host after a KVM guest is started. For example, a new domain can be > dynamically added to the configuration profile via the SE or an HMC > connected to a DPM enabled lpar. Likewise, AP adapters can be > dynamically configured (online state) and deconfigured (standby state) > using the SE, an SCLP command or an HMC connected to a DPM enabled > lpar. This can result in inadvertent sharing of AP queues between the > guest and host. > > 5. A root user can manually unbind an AP queue device representing a > queue in use by a KVM guest via the vfio_ap device driver's sysfs > unbind attribute. In this case, the guest will be using a queue that > is not bound to the driver which violates the device model. > > This patch series introduces the following changes to the current design > to alleviate the shortcomings described above as well as to implement > more of the AP architecture: > > 1. A root user will be prevented from making edits to the AP bus's > /sys/bus/ap/apmask or /sys/bus/ap/aqmask if the change would transfer > ownership of an APQN from the vfio_ap device driver to a zcrypt driver > while the APQN is assigned to a matrix mdev. > > 2. Allow a root user to hot plug/unplug AP adapters, domains and control > domains for a KVM guest using the matrix mdev via its sysfs > assign/unassign attributes. > > 4. Allow assignment of an AP adapter or domain to a matrix mdev even if > it results in assignment of an APQN that does not reference an AP > queue device bound to the vfio_ap device driver, as long as the APQN > is not reserved for use by the default zcrypt drivers (also known as > over-provisioning of AP resources). Allowing over-provisioning of AP > resources better models the architecture which does not preclude > assigning AP resources that are not yet available in the system. Such > APQNs, however, will not be assigned to the guest using the matrix > mdev; only APQNs referencing AP queue devices bound to the vfio_ap > device driver will actually get assigned to the guest. > > 5. Handle dynamic changes to the AP device model. > > 1. Rationale for changes to AP bus's apmask/aqmask interfaces: > ---------------------------------------------------------- > Due to the extremely sensitive nature of cryptographic data, it is > imperative that great care be taken to ensure that such data is secured. > Allowing a root user, either inadvertently or maliciously, to configure > these masks such that a queue is shared between the host and a guest is > not only avoidable, it is advisable. It was suggested that this scenario > is better handled in user space with management software, but that does > not preclude a malicious administrator from using the sysfs interfaces > to gain access to a guest's crypto data. It was also suggested that this > scenario could be avoided by taking access to the adapter away from the > guest and zeroing out the queues prior to the vfio_ap driver releasing the > device; however, stealing an adapter in use from a guest as a by-product > of an operation is bad and will likely cause problems for the guest > unnecessarily. It was decided that the most effective solution with the > least number of negative side effects is to prevent the situation at the > source. > > 2. Rationale for hot plug/unplug using matrix mdev sysfs interfaces: > ---------------------------------------------------------------- > Allowing a user to hot plug/unplug AP resources using the matrix mdev > sysfs interfaces circumvents the need to terminate the guest in order to > modify its AP configuration. Allowing dynamic configuration makes > reconfiguring a guest's AP matrix much less disruptive. > > 3. Rationale for allowing over-provisioning of AP resources: > ----------------------------------------------------------- > Allowing assignment of AP resources to a matrix mdev and ultimately to a > guest better models the AP architecture. The architecture does not > preclude assignment of unavailable AP resources. If a queue subsequently > becomes available while a guest using the matrix mdev to which its APQN > is assigned, the guest will be given access to it. If an APQN > is dynamically unassigned from the underlying host system, it will > automatically become unavailable to the guest. > > Change log v12-v13: > ------------------ > * Combined patches 12/13 from previous series into one patch > > * Moved all changes for linking queues and mdevs into a single patch > > * Re-ordered some patches to aid in review > > * Using mutex_trylock() function in adapter/domain assignment functions > to avoid potential deadlock condition with in_use callback > > * Using filtering function for refreshing the guest's APCB for all events > that change the APCB: assign/unassign adapters, domains, control domains; > bind/unbind of queue devices; and, changes to the host AP configuration. > > Change log v11-v12: > ------------------ > * Moved matrix device lock to protect group notifier callback > > * Split the 'No need to disable IRQ after queue reset' patch into > multiple patches for easier review (move probe/remove callback > functions and remove disable IRQ after queue reset) > > * Added code to decrement reference count for KVM in group notifier > callback > > * Using mutex_trylock() in functions implementing the sysfs assign_adapter > and assign_domain as well as the in_use callback to avoid deadlock > between the AP bus's ap_perms mutex and the matrix device lock used by > vfio_ap driver. > > * The sysfs guest_matrix attribute of the vfio_ap mdev will now display > the shadow APCB regardless of whether a guest is using the mdev or not > > * Replaced vfio_ap mdev filtering function with a function that initializes > the guest's APCB by filtering the vfio_ap mdev by APID. > > * No longer using filtering function during adapter/domain assignment > to/from the vfio_ap mdev; replaced with new hot plug/unplug > adapter/domain functions. > > * No longer using filtering function during bind/unbind; replaced with > hot plug/unplug queue functions. > > * No longer using filtering function for bulk assignment of new adapters > and domains in on_scan_complete callback; replaced with new hot plug > functions. > > > Change log v10-v11: > ------------------ > * The matrix mdev's configuration is not filtered by APID so that if any > APQN assigned to the mdev is not bound to the vfio_ap device driver, > the adapter will not get plugged into the KVM guest on startup, or when > a new adapter is assigned to the mdev. > > * Replaced patch 8 by squashing patches 8 (filtering patch) and 15 (handle > probe/remove). > > * Added a patch 1 to remove disable IRQ after a reset because the reset > already disables a queue. > > * Now using filtering code to update the KVM guest's matrix when > notified that AP bus scan has completed. > > * Fixed issue with probe/remove not inititiated by a configuration change > occurring within a config change. > > > Change log v9-v10: > ----------------- > * Updated the documentation in vfio-ap.rst to include information about the > AP dynamic configuration support > > Change log v8-v9: > ---------------- > * Fixed errors flagged by the kernel test robot > > * Fixed issue with guest losing queues when a new queue is probed due to > manual bind operation. > > Change log v7-v8: > ---------------- > * Now logging a message when an attempt to reserve APQNs for the zcrypt > drivers will result in taking a queue away from a KVM guest to provide > the sysadmin a way to ascertain why the sysfs operation failed. > > * Created locked and unlocked versions of the ap_parse_mask_str() function. > > * Now using new interface provided by an AP bus patch - > s390/ap: introduce new ap function ap_get_qdev() - to retrieve > struct ap_queue representing an AP queue device. This patch is not a > part of this series but is a prerequisite for this series. > > Change log v6-v7: > ---------------- > * Added callbacks to AP bus: > - on_config_changed: Notifies implementing drivers that > the AP configuration has changed since last AP device scan. > - on_scan_complete: Notifies implementing drivers that the device scan > has completed. > - implemented on_config_changed and on_scan_complete callbacks for > vfio_ap device driver. > - updated vfio_ap device driver's probe and remove callbacks to handle > dynamic changes to the AP device model. > * Added code to filter APQNs when assigning AP resources to a KVM guest's > CRYCB > > Change log v5-v6: > ---------------- > * Fixed a bug in ap_bus.c introduced with patch 2/7 of the v5 > series. Harald Freudenberer pointed out that the mutex lock > for ap_perms_mutex in the apmask_store and aqmask_store functions > was not being freed. > > * Removed patch 6/7 which added logging to the vfio_ap driver > to expedite acceptance of this series. The logging will be introduced > with a separate patch series to allow more time to explore options > such as DBF logging vs. tracepoints. > > * Added 3 patches related to ensuring that APQNs that do not reference > AP queue devices bound to the vfio_ap device driver are not assigned > to the guest CRYCB: > > Patch 4: Filter CRYCB bits for unavailable queue devices > Patch 5: sysfs attribute to display the guest CRYCB > Patch 6: update guest CRYCB in vfio_ap probe and remove callbacks > > * Added a patch (Patch 9) to version the vfio_ap module. > > * Reshuffled patches to allow the in_use callback implementation to > invoke the vfio_ap_mdev_verify_no_sharing() function introduced in > patch 2. > > Change log v4-v5: > ---------------- > * Added a patch to provide kernel s390dbf debug logs for VFIO AP > > Change log v3->v4: > ----------------- > * Restored patches preventing root user from changing ownership of > APQNs from zcrypt drivers to the vfio_ap driver if the APQN is > assigned to an mdev. > > * No longer enforcing requirement restricting guest access to > queues represented by a queue device bound to the vfio_ap > device driver. > > * Removed shadow CRYCB and now directly updating the guest CRYCB > from the matrix mdev's matrix. > > * Rebased the patch series on top of 'vfio: ap: AP Queue Interrupt > Control' patches. > > * Disabled bind/unbind sysfs interfaces for vfio_ap driver > > Change log v2->v3: > ----------------- > * Allow guest access to an AP queue only if the queue is bound to > the vfio_ap device driver. > > * Removed the patch to test CRYCB masks before taking the vCPUs > out of SIE. Now checking the shadow CRYCB in the vfio_ap driver. > > Change log v1->v2: > ----------------- > * Removed patches preventing root user from unbinding AP queues from > the vfio_ap device driver > * Introduced a shadow CRYCB in the vfio_ap driver to manage dynamic > changes to the AP guest configuration due to root user interventions > or hardware anomalies. > > Tony Krowiak (15): > s390/vfio-ap: clean up vfio_ap resources when KVM pointer invalidated > s390/vfio-ap: No need to disable IRQ after queue reset > s390/vfio-ap: move probe and remove callbacks to vfio_ap_ops.c > s390/vfio-ap: use new AP bus interface to search for queue devices > s390/vfio-ap: manage link between queue struct and matrix mdev > s390/vfio-ap: allow assignment of unavailable AP queues to mdev device > s390/vfio-ap: introduce shadow APCB > s390/vfio-ap: sysfs attribute to display the guest's matrix > s390/vfio-ap: allow hot plug/unplug of AP resources using mdev device > s390/zcrypt: driver callback to indicate resource in use > s390/vfio-ap: implement in-use callback for vfio_ap driver > s390/zcrypt: Notify driver on config changed and scan complete > callbacks > s390/vfio-ap: handle host AP config change notification > s390/vfio-ap: handle AP bus scan completed notification > s390/vfio-ap: update docs to include dynamic config support > > Documentation/s390/vfio-ap.rst | 383 ++++++++--- > drivers/s390/crypto/ap_bus.c | 251 +++++++- > drivers/s390/crypto/ap_bus.h | 16 + > drivers/s390/crypto/vfio_ap_drv.c | 50 +- > drivers/s390/crypto/vfio_ap_ops.c | 891 +++++++++++++++++--------- > drivers/s390/crypto/vfio_ap_private.h | 29 +- > 6 files changed, 1170 insertions(+), 450 deletions(-) >