From: Tony Krowiak <email@example.com> To: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Cc: email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: [PATCH v16 00/14] s390/vfio-ap: dynamic configuration support Date: Wed, 9 Jun 2021 07:36:27 -0400 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <email@example.com> PING! On 5/10/21 12:44 PM, Tony Krowiak wrote: > Note: Patch 1, "s390/vfio-ap: fix memory leak in mdev remove callback" > does not belong to this series. It is currently being reviewed > and is included here because it will be a pre-req for this series > when it is accepted and merged. > > 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 v15-v16: > ------------------ > * Added patch to reset queues after an adapter or domain is unassigned in > case of re-assignment to a different mdev (see patch description for > patch 9, "s390/vfio-ap: reset queues after adapter/domain unassignment"). > > * Fixed circular lockdep re-introduced by hot plugging of AP resources into > a KVM guest (see changes to vfio_ap_mdev_commit_apcb() function in patch > 8, "s390/vfio-ap: allow hot plug/unplug of AP resources using mdev > device"). > > > Change log v14-v15: > ------------------ > * Fixed bug: Unlink mdev from all queues when the mdev is removed. > > Change log v13-v14: > ------------------ > * Removed patch "s390/vfio-ap: clean up vfio_ap resources when KVM pointer > invalidated". The patch is not necessary because that is handled > with patch 1 of this series (currently being merged) and > commit f21916ec4826 ("s390/vfio-ap: clean up vfio_ap resources when KVM pointer invalidated") > > * Removed patch "s390/vfio-ap: No need to disable IRQ after queue reset", > that has already been merged with > commit 6c12a6384e0c ("s390/vfio-ap: No need to disable IRQ after queue reset"). > > * Initialize the vfio_ap_queue object before setting the drvdata in > the probe callback > > * Change return code from mdev assignment interfaces to -EAGAIN when > mutex_trylock fails for the mdev lock. > > * Restored missing hunk from v12 in the group notifier callback, but > had to restore it to the vfio_ap_mdev_set_kvm() function due to > changes made via merged commits noted above. > > * Reordered patch "s390/vfio-ap: sysfs attribute to display the > guest's matrix" to follow the patches that modify the shadow > APCB. > > * Remove queue from APCB before resetting it in the remove > callback. > > * Split the vfio_ap_mdev_unlink_queue() function into two > functions: one to remove the link from the matrix mdev to > the queue; and, one to remove the link from the queue to the matrix > mdev. > > * Removed the QCI call and the shadow_apcb memcpy from the > vfio_ap_mdev_filter_apcb() function. > > * Do not clear shadow_apcb when there are not adapters or domains > assigned. > > * Moved filtering code from "s390/vfio-ap: allow hot plug/unplug of > AP resources using mdev device" into its own patch. > > * Squashed the two patches comprising the handling of changes to > the AP configuration into one patch. > > * Added code to delay hot plug during probe until the AP bus scan > is complete if the APID of the queue is in the bitmap of adapters > currently being added to the AP configuration. > > 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 (14): > s390/vfio-ap: fix memory leak in mdev remove callback > s390/vfio-ap: use new AP bus interface to search for queue devices > s390/vfio-ap: move probe and remove callbacks to vfio_ap_ops.c > s390/vfio-ap: manage link between queue struct and matrix mdev > s390/vfio-ap: introduce shadow APCB > s390/vfio-ap: refresh guest's APCB by filtering APQNs assigned to mdev > s390/vfio-ap: allow assignment of unavailable AP queues to mdev device > s390/vfio-ap: allow hot plug/unplug of AP resources using mdev device > s390/vfio-ap: reset queues after adapter/domain unassignment > s390/zcrypt: driver callback to indicate resource in use > s390/vfio-ap: implement in-use callback for vfio_ap driver > s390/vfio-ap: sysfs attribute to display the guest's matrix > s390/zcrypt: notify drivers on config changed and scan complete > callbacks > s390/vfio-ap: update docs to include dynamic config support > > Documentation/s390/vfio-ap.rst | 383 +++++++--- > drivers/s390/crypto/ap_bus.c | 249 +++++- > drivers/s390/crypto/ap_bus.h | 16 + > drivers/s390/crypto/vfio_ap_drv.c | 46 +- > drivers/s390/crypto/vfio_ap_ops.c | 1008 ++++++++++++++++++------- > drivers/s390/crypto/vfio_ap_private.h | 28 +- > 6 files changed, 1322 insertions(+), 408 deletions(-) >
prev parent reply other threads:[~2021-06-09 11:36 UTC|newest] Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-10 16:44 Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 01/14] s390/vfio-ap: fix memory leak in mdev remove callback Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 02/14] s390/vfio-ap: use new AP bus interface to search for queue devices Tony Krowiak 2021-06-09 13:52 ` Jason J. Herne 2021-06-09 18:23 ` Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 03/14] s390/vfio-ap: move probe and remove callbacks to vfio_ap_ops.c Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 04/14] s390/vfio-ap: manage link between queue struct and matrix mdev Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 05/14] s390/vfio-ap: introduce shadow APCB Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 06/14] s390/vfio-ap: refresh guest's APCB by filtering APQNs assigned to mdev Tony Krowiak 2021-05-24 16:15 ` Halil Pasic 2021-06-01 11:25 ` Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 07/14] s390/vfio-ap: allow assignment of unavailable AP queues to mdev device Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 08/14] s390/vfio-ap: allow hot plug/unplug of AP resources using " Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 09/14] s390/vfio-ap: reset queues after adapter/domain unassignment Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 10/14] s390/zcrypt: driver callback to indicate resource in use Tony Krowiak 2021-05-19 11:58 ` Julian Wiedmann 2021-05-20 11:58 ` Harald Freudenberger 2021-05-20 15:28 ` Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 11/14] s390/vfio-ap: implement in-use callback for vfio_ap driver Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 12/14] s390/vfio-ap: sysfs attribute to display the guest's matrix Tony Krowiak 2021-05-10 16:44 ` [PATCH v16 13/14] s390/zcrypt: notify drivers on config changed and scan complete callbacks Tony Krowiak 2021-05-10 20:02 ` kernel test robot 2021-05-10 16:44 ` [PATCH v16 14/14] s390/vfio-ap: update docs to include dynamic config support Tony Krowiak 2021-05-18 13:26 ` [PATCH v16 00/14] s390/vfio-ap: dynamic configuration support Tony Krowiak 2021-05-18 16:54 ` Halil Pasic 2021-05-19 11:52 ` Tony Krowiak 2021-06-09 11:36 ` Tony Krowiak [this message]
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