- 28 Jul, 2022 8 commits
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Alexander Gordeev authored
Add "Lowcore Area Start" and "Lowcore Area End" markers that fence pages where absolute lowcore resides. Reviewed-by:
Heiko Carstens <hca@linux.ibm.com> Signed-off-by:
Alexander Gordeev <agordeev@linux.ibm.com>
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Alexander Gordeev authored
Temporary unsetting of the prefix page in memcpy_absolute() routine poses a risk of executing code path with unexpectedly disabled prefix page. This rework avoids the prefix page uninstalling and disabling of normal and machine check interrupts when accessing the absolute zero memory. Although memcpy_absolute() routine can access the whole memory, it is only used to update the absolute zero lowcore. This rework therefore introduces a new mechanism for the absolute zero lowcore access and scraps memcpy_absolute() routine for good. Instead, an area is reserved in the virtual memory that is used for the absolute lowcore access only. That area holds an array of 8KB virtual mappings - one per CPU. Whenever a CPU is brought online, the corresponding item is mapped to the real address of the previously installed prefix page. The absolute zero lowcore access works like this: a CPU calls the new primitive get_abs_lowcore() to obtain its 8KB mapping as a pointer to the struct lowcore. Virtual address references to that pointer get translated to the real addresses of the prefix page, which in turn gets swapped with the absolute zero memory addresses due to prefixing. Once the pointer is not needed it must be released with put_abs_lowcore() primitive: struct lowcore *abs_lc; unsigned long flags; abs_lc = get_abs_lowcore(&flags); abs_lc->... = ...; put_abs_lowcore(abs_lc, flags); To ensure the described mechanism works large segment- and region- table entries must be avoided for the 8KB mappings. Failure to do so results in usage of Region-Frame Absolute Address (RFAA) or Segment-Frame Absolute Address (SFAA) large page fields. In that case absolute addresses would be used to address the prefix page instead of the real ones and the prefixing would get bypassed. Reviewed-by:
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Alexander Gordeev authored
Make the absolute lowcore assignments immediately follow the boot CPU lowcore same member assignments. This way readability improves when reading from up to down, with no out of order mcck stack allocation in-between. Reviewed-by:
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Alexander Gordeev authored
Uncouple input and output arguments by making the latter the function return value. Reviewed-by:
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Alexander Gordeev authored
As result of commit 915fea04 ("s390/smp: enable DAT before CPU restart callback is called") the low-address protection bit gets mistakenly unset in control register 0 save area of the absolute zero memory. That area is used when manual PSW restart happened to hit an offline CPU. In this case the low-address protection for that CPU will be dropped. Reviewed-by:
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Jason Wang authored
Remove duplicated `that' in a comment Signed-off-by:
Jason Wang <wangborong@cdjrlc.com> Link: https://lore.kernel.org/r/20220715053838.5005-1-wangborong@cdjrlc.com [agordeev@linux.ibm.com rephrased commit message] Signed-off-by:
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Randy Dunlap authored
Use the possessive "its" instead of the contraction "it's" where appropriate. Signed-off-by:
Randy Dunlap <rdunlap@infradead.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: linux-s390@vger.kernel.org Link: https://lore.kernel.org/r/20220715020010.12678-1-rdunlap@infradead.orgSigned-off-by:
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Alexander Gordeev authored
Pull changes that finalize switching of copy_oldmem_page() callback to iov_iter interface. These changes were pulled in work.iov_iter of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.gitSigned-off-by:
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- 22 Jul, 2022 2 commits
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Alexander Gordeev authored
Fix multiple warnings produced by make htmldocs Fixes: cb269e0a ("s390/vfio-ap: update docs to include dynamic config support") Signed-off-by:
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Alexander Gordeev authored
Fix multiple warnings produced by make htmldocs Fixes: e32d3827 ("s390/Docs: new doc describing lock usage by the vfio_ap device driver") Signed-off-by:
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- 20 Jul, 2022 7 commits
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Alexander Gordeev authored
Make it possible to handle not only single-, but also multi- segment iterators in copy_oldmem_iter() callback. Change the semantics of called functions to match the iterator model - instead of an error code the exact number of bytes copied is returned. The swap page used to copy data to user space is adopted for kernel space too. That does not bring any performance impact. Suggested-by:
Matthew Wilcox <willy@infradead.org> Fixes: cc02e6e2 ("s390/crash: add missing iterator advance in copy_oldmem_page()") Acked-by:
Alexander Egorenkov <egorenar@linux.ibm.com> Link: https://lore.kernel.org/r/5af6da3a0bffe48a90b0b7139ecf6a818b2d18e8.1658206891.git.agordeev@linux.ibm.comSigned-off-by:
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Alexander Gordeev authored
Currently a temporary page-size buffer is allocated for copying oldmem to user space. That limits copy_to_user_real() operation only to stages when virtual memory is available and still makes it possible to fail while the system is being dumped. Instead of reallocating single page on each copy_oldmem_page() iteration use a statically allocated buffer. This also paves the way for a further memcpy_real() rework where no swap buffer is needed altogether. Acked-by:
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Alexander Gordeev authored
Function copy_to_user_real() does not really belong to maccess.c. It is only used for copying oldmem to user space, so let's move it to the friends. Acked-by:
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Alexander Gordeev authored
Memory buffer used for reading out data from hardware system area is not protected against concurrent access. Reported-by:
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Alexander Gordeev authored
The number of bytes in a chunk is correctly calculated, but instead the total number of bytes is passed to copy_to_user_real() function. Reported-by:
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Alexander Gordeev authored
Make save_area_alloc() return classic NULL on allocation failure. The only caller smp_save_dump_cpus() does check the return value already and panics if NULL is returned. Reviewed-by:
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Alexander Gordeev authored
Since commit 461e0da7ddbb ("s390: remove broken hibernate / power management support") there are no users of tprot() left. Remove the function itself as well. Acked-by:
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- 19 Jul, 2022 23 commits
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Steffen Eiden authored
Make sure the uvdevice driver will be automatically loaded when facility 158 is available. Signed-off-by:
Steffen Eiden <seiden@linux.ibm.com> Reviewed-by:
Claudio Imbrenda <imbrenda@linux.ibm.com> Link: https://lore.kernel.org/r/20220713125644.16121-4-seiden@linux.ibm.comSigned-off-by:
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Heiko Carstens authored
Allow for facility bits to be used in cpu features. Signed-off-by:
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Heiko Carstens authored
Rework cpufeature implementation to allow for various cpu feature indications, which is not only limited to hwcap bits. This is achieved by adding a sequential list of cpu feature numbers, where each of them is mapped to an entry which indicates what this number is about. Each entry contains a type member, which indicates what feature name space to look into (e.g. hwcap, or cpu facility). If wanted this allows also to automatically load modules only in e.g. z/VM configurations. Signed-off-by:
Hendrik Brueckner <brueckner@linux.ibm.com> Link: https://lore.kernel.org/r/20220713125644.16121-2-seiden@linux.ibm.comSigned-off-by:
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Tony Krowiak authored
A new document, Documentation/s390/vfio-ap-locking.rst was added. Make sure the new document is picked up for the VFIO AP maintainers by using a wildcard: Documentation/s390/vfio-ap*. Signed-off-by:
Tony Krowiak <akrowiak@linux.ibm.com> Signed-off-by:
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Tony Krowiak authored
Introduces a new document describing the locks used by the vfio_ap device driver and how to use them so as to avoid lockdep reports and deadlock situations. Signed-off-by:
Jason J. Herne <jjherne@linux.ibm.com> Signed-off-by:
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Tony Krowiak authored
Update the documentation in vfio-ap.rst to include information about the AP dynamic configuration support (e.g., hot plug of adapters, domains and control domains via the matrix mediated device's sysfs assignment attributes). This patch also makes a few minor tweaks to make corrections and clarifications. Signed-off-by:
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Tony Krowiak authored
This patch implements two new AP driver callbacks: void (*on_config_changed)(struct ap_config_info *new_config_info, struct ap_config_info *old_config_info); void (*on_scan_complete)(struct ap_config_info *new_config_info, struct ap_config_info *old_config_info); The on_config_changed callback is invoked at the start of the AP bus scan function when it determines that the host AP configuration information has changed since the previous scan. The vfio_ap device driver registers a callback function for this callback that performs the following operations: 1. Unplugs the adapters, domains and control domains removed from the host's AP configuration from the guests to which they are assigned in a single operation. 2. Stores bitmaps identifying the adapters, domains and control domains added to the host's AP configuration with the structure representing the mediated device. When the vfio_ap device driver's probe callback is subsequently invoked, the probe function will recognize that the queue is being probed due to a change in the host's AP configuration and the plugging of the queue into the guest will be bypassed. The on_scan_complete callback is invoked after the ap bus scan is completed if the host AP configuration data has changed. The vfio_ap device driver registers a callback function for this callback that hot plugs each queue and control domain added to the AP configuration for each guest using them in a single hot plug operation. Signed-off-by: -
Tony Krowiak authored
The matrix of adapters and domains configured in a guest's APCB may differ from the matrix of adapters and domains assigned to the matrix mdev, so this patch introduces a sysfs attribute to display the matrix of adapters and domains that are or will be assigned to the APCB of a guest that is or will be using the matrix mdev. For a matrix mdev denoted by $uuid, the guest matrix can be displayed as follows: cat /sys/devices/vfio_ap/matrix/$uuid/guest_matrix Signed-off-by:
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Tony Krowiak authored
Let's implement the callback to indicate when an APQN is in use by the vfio_ap device driver. The callback is invoked whenever a change to the apmask or aqmask would result in one or more queue devices being removed from the driver. The vfio_ap device driver will indicate a resource is in use if the APQN of any of the queue devices to be removed are assigned to any of the matrix mdevs under the driver's control. There is potential for a deadlock condition between the matrix_dev->guests_lock used to lock the guest during assignment of adapters and domains and the ap_perms_mutex locked by the AP bus when changes are made to the sysfs apmask/aqmask attributes. The AP Perms lock controls access to the objects that store the adapter numbers (ap_perms) and domain numbers (aq_perms) for the sysfs /sys/bus/ap/apmask and /sys/bus/ap/aqmask attributes. These attributes identify which queues are reserved for the zcrypt default device drivers. Before allowing a bit to be removed from either mask, the AP bus must check with the vfio_ap device driver to verify that none of the queues are assigned to any of its mediated devices. The apmask/aqmask attributes can be written or read at any time from userspace, so care must be taken to prevent a deadlock with asynchronous operations that might be taking place in the vfio_ap device driver. For example, consider the following: 1. A system administrator assigns an adapter to a mediated device under the control of the vfio_ap device driver. The driver will need to first take the matrix_dev->guests_lock to potentially hot plug the adapter into the KVM guest. 2. At the same time, a system administrator sets a bit in the sysfs /sys/bus/ap/ap_mask attribute. To complete the operation, the AP bus must: a. Take the ap_perms_mutex lock to update the object storing the values for the /sys/bus/ap/ap_mask attribute. b. Call the vfio_ap device driver's in-use callback to verify that the queues now being reserved for the default zcrypt drivers are not assigned to a mediated device owned by the vfio_ap device driver. To do the verification, the in-use callback function takes the matrix_dev->guests_lock, but has to wait because it is already held by the operation in 1 above. 3. The vfio_ap device driver calls an AP bus function to verify that the new queues resulting from the assignment of the adapter in step 1 are not reserved for the default zcrypt device driver. This AP bus function tries to take the ap_perms_mutex lock but gets stuck waiting for the waiting for the lock due to step 2a above. Consequently, we have the following deadlock situation: matrix_dev->guests_lock locked (1) ap_perms_mutex lock locked (2a) Waiting for matrix_dev->gusts_lock (2b) which is currently held (1) Waiting for ap_perms_mutex lock (3) which is currently held (2a) To prevent this deadlock scenario, the function called in step 3 will no longer take the ap_perms_mutex lock and require the caller to take the lock. The lock will be the first taken by the adapter/domain assignment functions in the vfio_ap device driver to maintain the proper locking order. Signed-off-by: -
Tony Krowiak authored
When an adapter or domain is unassigned from an mdev attached to a KVM guest, one or more of the guest's queues may get dynamically removed. Since the removed queues could get re-assigned to another mdev, they need to be reset. So, when an adapter or domain is unassigned from the mdev, the queues that are removed from the guest's AP configuration (APCB) will be reset. Signed-off-by:
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Tony Krowiak authored
When an AP queue device is probed or removed, if the mediated device is attached to a KVM guest, the mediated device's adapter, domain and control domain bitmaps must be filtered to update the guest's APCB and if any changes are detected, the guest's APCB must then be hot plugged into the guest to reflect those changes to the guest. Signed-off-by:
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Tony Krowiak authored
Let's hot plug an adapter, domain or control domain into the guest when it is assigned to a matrix mdev that is attached to a KVM guest. Likewise, let's hot unplug an adapter, domain or control domain from the guest when it is unassigned from a matrix_mdev that is attached to a KVM guest. Whenever an assignment or unassignment of an adapter, domain or control domain is performed, the APQNs and control domains assigned to the matrix mdev will be filtered and assigned to the AP control block (APCB) that supplies the AP configuration to the guest so that no adapter, domain or control domain that is not in the host's AP configuration nor any APQN that does not reference a queue device bound to the vfio_ap device driver is assigned. After updating the APCB, if the mdev is in use by a KVM guest, it is hot plugged into the guest to dynamically provide access to the adapters, domains and control domains provided via the newly refreshed APCB. Signed-off-by:
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Tony Krowiak authored
The callback functions for probing and removing a queue device must take and release the locks required to perform a dynamic update of a guest's APCB in the proper order. The proper order for taking the locks is: matrix_dev->guests_lock => kvm->lock => matrix_dev->mdevs_lock The proper order for releasing the locks is: matrix_dev->mdevs_lock => kvm->lock => matrix_dev->guests_lock A new helper function is introduced to be used by the probe callback to acquire the required locks. Since the probe callback only has access to a queue device when it is called, the helper function will find the ap_matrix_mdev object to which the queue device's APQN is assigned and return it so the KVM guest to which the mdev is attached can be dynamically updated. Note that in order to find the ap_matrix_mdev (matrix_mdev) object, it is necessary to search the matrix_dev->mdev_list. This presents a locking order dilemma because the matrix_dev->mdevs_lock can't be taken to protect against changes to the list while searching for the matrix_mdev to which a queue device's APQN is assigned. This is due to the fact that the proper locking order requires that the matrix_dev->mdevs_lock be taken after both the matrix_mdev->kvm->lock and the matrix_dev->mdevs_lock. Consequently, the matrix_dev->guests_lock will be used to protect against removal of a matrix_mdev object from the list while a queue device is being probed. This necessitates changes to the mdev probe/remove callback functions to take the matrix_dev->guests_lock prior to removing a matrix_mdev object from the list. A new macro is also introduced to acquire the locks required to dynamically update the guest's APCB in the proper order when a queue device is removed. Signed-off-by: -
Tony Krowiak authored
The functions backing the matrix mdev's sysfs attribute interfaces to assign/unassign adapters, domains and control domains must take and release the locks required to perform a dynamic update of a guest's APCB in the proper order. The proper order for taking the locks is: matrix_dev->guests_lock => kvm->lock => matrix_dev->mdevs_lock The proper order for releasing the locks is: matrix_dev->mdevs_lock => kvm->lock => matrix_dev->guests_lock Two new macros are introduced for this purpose: One to take the locks and the other to release the locks. These macros will be used by the assignment/unassignment functions to prepare for dynamic update of the KVM guest's APCB. Signed-off-by:
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Tony Krowiak authored
The group notifier that handles the VFIO_GROUP_NOTIFY_SET_KVM event must use the required locks in proper locking order to dynamically update the guest's APCB. The proper locking order is: 1. matrix_dev->guests_lock: required to use the KVM pointer to update a KVM guest's APCB. 2. matrix_mdev->kvm->lock: required to update a KVM guest's APCB. 3. matrix_dev->mdevs_lock: required to store or access the data stored in a struct ap_matrix_mdev instance. Two macros are introduced to acquire and release the locks in the proper order. These macros are now used by the group notifier functions. Signed-off-by: -
Tony Krowiak authored
The vfio_ap device driver registers for notification when the pointer to the KVM object for a guest is set. Recall that the KVM lock (kvm->lock) mutex must be taken outside of the matrix_dev->lock mutex to prevent the reporting by lockdep of a circular locking dependency (a.k.a., a lockdep splat): * see commit 0cc00c8d ("Fix circular lockdep when setting/clearing crypto masks") * see commit 86956e70 ("replace open coded locks for VFIO_GROUP_NOTIFY_SET_KVM notification") With the introduction of support for hot plugging/unplugging AP devices passed through to a KVM guest, a new guests_lock mutex is introduced to ensure the proper locking order is maintained: struct ap_matrix_dev { ... struct mutex guests_lock; ... } The matrix_dev->guests_lock controls access to the matrix_mdev instances that hold the state for AP devices that have been passed through to a KVM guest. This lock must be held to control access to the KVM pointer (matrix_mdev->kvm) while the vfio_ap device driver is using it to plug/unplug AP devices passed through to the KVM guest. Keep in mind, the proper locking order must be maintained whenever dynamically updating a KVM guest's APCB to plug/unplug adapters, domains and control domains: 1. matrix_dev->guests_lock: required to use the KVM pointer - stored in a struct ap_matrix_mdev instance - to update a KVM guest's APCB 2. matrix_mdev->kvm->lock: required to update a guest's APCB 3. matrix_dev->mdevs_lock: required to access data stored in a struct ap_matrix_mdev instance. Signed-off-by:
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Tony Krowiak authored
The matrix_dev->lock mutex is being renamed to matrix_dev->mdevs_lock to better reflect its purpose, which is to control access to the state of the mediated devices under the control of the vfio_ap device driver. Signed-off-by:
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Tony Krowiak authored
The current implementation does not allow assignment of an AP adapter or domain to an mdev device if each APQN resulting from the assignment does not reference an AP queue device that is bound to the vfio_ap device driver. This patch allows assignment of AP resources to the matrix mdev as long as the APQNs resulting from the assignment: 1. Are not reserved by the AP BUS for use by the zcrypt device drivers. 2. Are not assigned to another matrix mdev. The rationale behind this is that the AP architecture does not preclude assignment of APQNs to an AP configuration profile that are not available to the system. Signed-off-by:
Halil Pasic <pasic@linux.ibm.com> Signed-off-by:
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Tony Krowiak authored
Refresh the guest's APCB by filtering the APQNs and control domain numbers assigned to the matrix mdev. Filtering of APQNs: ----------------- APQNs that do not reference an AP queue device bound to the vfio_ap device driver must be filtered from the APQNs assigned to the matrix mdev before they can be assigned to the guest's APCB. Given that the APQNs are configured in the guest's APCB as a matrix of APIDs (adapters) and APQIs (domains), it is not possible to filter an individual APQN. For example, suppose the matrix of APQNs is structured as follows: APIDs 3 4 5 0 (3,0) (4,0) (5,0) APQIs 1 (3,1) (4,1) (5,1) 2 (3,2) (4,2) (5,2) Now suppose APQN (4,1) does not reference a queue device bound to the vfio_ap device driver. If we filter APID 4, the APQNs (4,0), (4,1) and (4,2) will be removed. Similarly, if we filter domain 1, APQNs (3,1), (4,1) and (5,1) will be removed. To resolve this dilemma, the choice was made to filter the APID - in this case 4 - from the guest's APCB. The reason for this design decision is because the APID references an AP adapter which is a real hardware device that can be physically installed, removed, enabled or disabled; whereas, a domain is a partition within the adapter. It therefore better reflects reality to remove the APID from the guest's APCB. Filtering of control domains: ---------------------------- Any control domains that are not assigned to the host's AP configuration will be filtered from those assigned to the matrix mdev before assigning them to the guest's APCB. Signed-off-by: -
Tony Krowiak authored
The APCB is a field within the CRYCB that provides the AP configuration to a KVM guest. Let's introduce a shadow copy of the KVM guest's APCB and maintain it for the lifespan of the guest. The shadow APCB serves the following purposes: 1. The shadow APCB can be maintained even when the mediated device is not currently in use by a KVM guest. Since the mediated device's AP configuration is filtered to ensure that no AP queues are passed through to the KVM guest that are not bound to the vfio_ap device driver or available to the host, the mediated device's AP configuration may differ from the guest's. Having a shadow of a guest's APCB allows us to provide a sysfs interface to view the guest's APCB even if the mediated device is not currently passed through to a KVM guest. This can aid in problem determination when the guest is unexpectedly missing AP resources. 2. If filtering was done in-place for the real APCB, the guest could pick up a transient state. Doing the filtering on a shadow and transferring the AP configuration to the real APCB after the guest is started or when AP resources are assigned to or unassigned from the mediated device, or when the host configuration changes, the guest's AP configuration will never be in a transient state. Signed-off-by:
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Tony Krowiak authored
Let's create links between each queue device bound to the vfio_ap device driver and the matrix mdev to which the queue's APQN is assigned. The idea is to facilitate efficient retrieval of the objects representing the queue devices and matrix mdevs as well as to verify that a queue assigned to a matrix mdev is bound to the driver. The links will be created as follows: * When the queue device is probed, if its APQN is assigned to a matrix mdev, the structures representing the queue device and the matrix mdev will be linked. * When an adapter or domain is assigned to a matrix mdev, for each new APQN assigned that references a queue device bound to the vfio_ap device driver, the structures representing the queue device and the matrix mdev will be linked. The links will be removed as follows: * When the queue device is removed, if its APQN is assigned to a matrix mdev, the link from the structure representing the matrix mdev to the structure representing the queue will be removed. Since the storage allocated for the vfio_ap_queue will be freed, there is no need to remove the link to the matrix_mdev to which the queue's APQN is assigned. * When an adapter or domain is unassigned from a matrix mdev, for each APQN unassigned that references a queue device bound to the vfio_ap device driver, the structures representing the queue device and the matrix mdev will be unlinked. * When an mdev is removed, the link from any queues assigned to the mdev to the mdev will be removed. Signed-off-by:
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Tony Krowiak authored
Let's move the probe and remove callbacks into the vfio_ap_ops.c file to keep all code related to managing queues in a single file. This way, all functions related to queue management can be removed from the vfio_ap_private.h header file defining the public interfaces for the vfio_ap device driver. Signed-off-by:
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Tony Krowiak authored
This patch refactors the vfio_ap device driver to use the AP bus's ap_get_qdev() function to retrieve the vfio_ap_queue struct containing information about a queue that is bound to the vfio_ap device driver. The bus's ap_get_qdev() function retrieves the queue device from a hashtable keyed by APQN. This is much more efficient than looping over the list of devices attached to the AP bus by several orders of magnitude. Signed-off-by:
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