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author | Linus Torvalds <torvalds@linux-foundation.org> | 2022-08-06 17:05:21 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-08-06 17:05:21 -0700 |
commit | 24cb958695724ffb4488ef4f65892c0767bcd2f2 (patch) | |
tree | 87fdf68a4a2b37ba855c99415c890d8c6d3218ef | |
parent | d77771c926671e0362af3fe792391be66072b242 (diff) | |
parent | 953503751a426413ea8aee2299ae3ee971b70d9b (diff) | |
download | linux-24cb958695724ffb4488ef4f65892c0767bcd2f2.tar.gz linux-24cb958695724ffb4488ef4f65892c0767bcd2f2.tar.bz2 linux-24cb958695724ffb4488ef4f65892c0767bcd2f2.zip |
Merge tag 's390-5.20-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
Pull s390 updates from Alexander Gordeev:
- Rework copy_oldmem_page() callback to take an iov_iter.
This includes a few prerequisite updates and fixes to the oldmem
reading code.
- Rework cpufeature implementation to allow for various CPU feature
indications, which is not only limited to hardware capabilities, but
also allows CPU facilities.
- Use the cpufeature rework to autoload Ultravisor module when CPU
facility 158 is available.
- Add ELF note type for encrypted CPU state of a protected virtual CPU.
The zgetdump tool from s390-tools package will decrypt the CPU state
using a Customer Communication Key and overwrite respective notes to
make the data accessible for crash and other debugging tools.
- Use vzalloc() instead of vmalloc() + memset() in ChaCha20 crypto
test.
- Fix incorrect recovery of kretprobe modified return address in
stacktrace.
- Switch the NMI handler to use generic irqentry_nmi_enter() and
irqentry_nmi_exit() helper functions.
- Rework the cryptographic Adjunct Processors (AP) pass-through design
to support dynamic changes to the AP matrix of a running guest as
well as to implement more of the AP architecture.
- Minor boot code cleanups.
- Grammar and typo fixes to hmcdrv and tape drivers.
* tag 's390-5.20-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (46 commits)
Revert "s390/smp: enforce lowcore protection on CPU restart"
Revert "s390/smp: rework absolute lowcore access"
Revert "s390/smp,ptdump: add absolute lowcore markers"
s390/unwind: fix fgraph return address recovery
s390/nmi: use irqentry_nmi_enter()/irqentry_nmi_exit()
s390: add ELF note type for encrypted CPU state of a PV VCPU
s390/smp,ptdump: add absolute lowcore markers
s390/smp: rework absolute lowcore access
s390/setup: rearrange absolute lowcore initialization
s390/boot: cleanup adjust_to_uv_max() function
s390/smp: enforce lowcore protection on CPU restart
s390/tape: fix comment typo
s390/hmcdrv: fix Kconfig "its" grammar
s390/docs: fix warnings for vfio_ap driver doc
s390/docs: fix warnings for vfio_ap driver lock usage doc
s390/crash: support multi-segment iterators
s390/crash: use static swap buffer for copy_to_user_real()
s390/crash: move copy_to_user_real() to crash_dump.c
s390/zcore: fix race when reading from hardware system area
s390/crash: fix incorrect number of bytes to copy to user space
...
43 files changed, 1842 insertions, 821 deletions
diff --git a/Documentation/s390/index.rst b/Documentation/s390/index.rst index b10ca9192557..73c79bf586fd 100644 --- a/Documentation/s390/index.rst +++ b/Documentation/s390/index.rst @@ -12,6 +12,7 @@ s390 Architecture qeth s390dbf vfio-ap + vfio-ap-locking vfio-ccw zfcpdump common_io diff --git a/Documentation/s390/vfio-ap-locking.rst b/Documentation/s390/vfio-ap-locking.rst new file mode 100644 index 000000000000..0dfcdb562e21 --- /dev/null +++ b/Documentation/s390/vfio-ap-locking.rst @@ -0,0 +1,115 @@ +.. SPDX-License-Identifier: GPL-2.0 + +====================== +VFIO AP Locks Overview +====================== +This document describes the locks that are pertinent to the secure operation +of the vfio_ap device driver. Throughout this document, the following variables +will be used to denote instances of the structures herein described: + +.. code-block:: c + + struct ap_matrix_dev *matrix_dev; + struct ap_matrix_mdev *matrix_mdev; + struct kvm *kvm; + +The Matrix Devices Lock (drivers/s390/crypto/vfio_ap_private.h) +--------------------------------------------------------------- + +.. code-block:: c + + struct ap_matrix_dev { + ... + struct list_head mdev_list; + struct mutex mdevs_lock; + ... + } + +The Matrix Devices Lock (matrix_dev->mdevs_lock) is implemented as a global +mutex contained within the single object of struct ap_matrix_dev. This lock +controls access to all fields contained within each matrix_mdev +(matrix_dev->mdev_list). This lock must be held while reading from, writing to +or using the data from a field contained within a matrix_mdev instance +representing one of the vfio_ap device driver's mediated devices. + +The KVM Lock (include/linux/kvm_host.h) +--------------------------------------- + +.. code-block:: c + + struct kvm { + ... + struct mutex lock; + ... + } + +The KVM Lock (kvm->lock) controls access to the state data for a KVM guest. This +lock must be held by the vfio_ap device driver while one or more AP adapters, +domains or control domains are being plugged into or unplugged from the guest. + +The KVM pointer is stored in the in the matrix_mdev instance +(matrix_mdev->kvm = kvm) containing the state of the mediated device that has +been attached to the KVM guest. + +The Guests Lock (drivers/s390/crypto/vfio_ap_private.h) +----------------------------------------------------------- + +.. code-block:: c + + struct ap_matrix_dev { + ... + struct list_head mdev_list; + struct mutex guests_lock; + ... + } + +The Guests Lock (matrix_dev->guests_lock) controls access to the +matrix_mdev instances (matrix_dev->mdev_list) that represent mediated devices +that hold the state for the mediated devices that have been attached to a +KVM guest. This lock must be held: + +1. 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. + +2. To add matrix_mdev instances to or remove them from matrix_dev->mdev_list. + This is necessary to ensure the proper locking order when the list is perused + to find an ap_matrix_mdev instance for the purpose of plugging/unplugging + AP devices passed through to a KVM guest. + + For example, when a queue device is removed from the vfio_ap device driver, + if the adapter is passed through to a KVM guest, it will have to be + unplugged. In order to figure out whether the adapter is passed through, + the matrix_mdev object to which the queue is assigned will have to be + found. The KVM pointer (matrix_mdev->kvm) can then be used to determine if + the mediated device is passed through (matrix_mdev->kvm != NULL) and if so, + to unplug the adapter. + +It is not necessary to take the Guests Lock to access the KVM pointer if the +pointer is not used to plug/unplug devices passed through to the KVM guest; +however, in this case, the Matrix Devices Lock (matrix_dev->mdevs_lock) must be +held in order to access the KVM pointer since it is set and cleared under the +protection of the Matrix Devices Lock. A case in point is the function that +handles interception of the PQAP(AQIC) instruction sub-function. This handler +needs to access the KVM pointer only for the purposes of setting or clearing IRQ +resources, so only the matrix_dev->mdevs_lock needs to be held. + +The PQAP Hook Lock (arch/s390/include/asm/kvm_host.h) +----------------------------------------------------- + +.. code-block:: c + + typedef int (*crypto_hook)(struct kvm_vcpu *vcpu); + + struct kvm_s390_crypto { + ... + struct rw_semaphore pqap_hook_rwsem; + crypto_hook *pqap_hook; + ... + }; + +The PQAP Hook Lock is a r/w semaphore that controls access to the function +pointer of the handler ``(*kvm->arch.crypto.pqap_hook)`` to invoke when the +PQAP(AQIC) instruction sub-function is intercepted by the host. The lock must be +held in write mode when pqap_hook value is set, and in read mode when the +pqap_hook function is called. diff --git a/Documentation/s390/vfio-ap.rst b/Documentation/s390/vfio-ap.rst index f57ae621f33e..61a0a3c6c7b4 100644 --- a/Documentation/s390/vfio-ap.rst +++ b/Documentation/s390/vfio-ap.rst @@ -123,27 +123,24 @@ Let's now take a look at how AP instructions executed on a guest are interpreted by the hardware. A satellite control block called the Crypto Control Block (CRYCB) is attached to -our main hardware virtualization control block. The CRYCB contains three fields -to identify the adapters, usage domains and control domains assigned to the KVM -guest: +our main hardware virtualization control block. The CRYCB contains an AP Control +Block (APCB) that has three fields to identify the adapters, usage domains and +control domains assigned to the KVM guest: * The AP Mask (APM) field is a bit mask that identifies the AP adapters assigned - to the KVM guest. Each bit in the mask, from left to right (i.e. from most - significant to least significant bit in big endian order), corresponds to + to the KVM guest. Each bit in the mask, from left to right, corresponds to an APID from 0-255. If a bit is set, the corresponding adapter is valid for use by the KVM guest. * The AP Queue Mask (AQM) field is a bit mask identifying the AP usage domains - assigned to the KVM guest. Each bit in the mask, from left to right (i.e. from - most significant to least significant bit in big endian order), corresponds to - an AP queue index (APQI) from 0-255. If a bit is set, the corresponding queue - is valid for use by the KVM guest. + assigned to the KVM guest. Each bit in the mask, from left to right, + corresponds to an AP queue index (APQI) from 0-255. If a bit is set, the + corresponding queue is valid for use by the KVM guest. * The AP Domain Mask field is a bit mask that identifies the AP control domains assigned to the KVM guest. The ADM bit mask controls which domains can be changed by an AP command-request message sent to a usage domain from the - guest. Each bit in the mask, from left to right (i.e. from most significant to - least significant bit in big endian order), corresponds to a domain from + guest. Each bit in the mask, from left to right, corresponds to a domain from 0-255. If a bit is set, the corresponding domain can be modified by an AP command-request message sent to a usage domain. @@ -151,10 +148,10 @@ If you recall from the description of an AP Queue, AP instructions include an APQN to identify the AP queue to which an AP command-request message is to be sent (NQAP and PQAP instructions), or from which a command-reply message is to be received (DQAP instruction). The validity of an APQN is defined by the matrix -calculated from the APM and AQM; it is the cross product of all assigned adapter -numbers (APM) with all assigned queue indexes (AQM). For example, if adapters 1 -and 2 and usage domains 5 and 6 are assigned to a guest, the APQNs (1,5), (1,6), -(2,5) and (2,6) will be valid for the guest. +calculated from the APM and AQM; it is the Cartesian product of all assigned +adapter numbers (APM) with all assigned queue indexes (AQM). For example, if +adapters 1 and 2 and usage domains 5 and 6 are assigned to a guest, the APQNs +(1,5), (1,6), (2,5) and (2,6) will be valid for the guest. The APQNs can provide secure key functionality - i.e., a private key is stored on the adapter card for each of its domains - so each APQN must be assigned to @@ -192,7 +189,7 @@ The design introduces three new objects: 1. AP matrix device 2. VFIO AP device driver (vfio_ap.ko) -3. VFIO AP mediated matrix pass-through device +3. VFIO AP mediated pass-through device The VFIO AP device driver ------------------------- @@ -200,12 +197,13 @@ The VFIO AP (vfio_ap) device driver serves the following purposes: 1. Provides the interfaces to secure APQNs for exclusive use of KVM guests. -2. Sets up the VFIO mediated device interfaces to manage a mediated matrix +2. Sets up the VFIO mediated device interfaces to manage a vfio_ap mediated device and creates the sysfs interfaces for assigning adapters, usage domains, and control domains comprising the matrix for a KVM guest. -3. Configures the APM, AQM and ADM in the CRYCB referenced by a KVM guest's - SIE state description to grant the guest access to a matrix of AP devices +3. Configures the APM, AQM and ADM in the APCB contained in the CRYCB referenced + by a KVM guest's SIE state description to grant the guest access to a matrix + of AP devices Reserve APQNs for exclusive use of KVM guests --------------------------------------------- @@ -235,10 +233,10 @@ reserved:: | | 8 probe | | +--------^---------+ +--^--^------------+ 6 edit | | | - apmask | +-----------------------------+ | 9 mdev create + apmask | +-----------------------------+ | 11 mdev create aqmask | | 1 modprobe | +--------+-----+---+ +----------------+-+ +----------------+ - | | | |8 create | mediated | + | | | |10 create| mediated | | admin | | VFIO device core |---------> matrix | | + | | | device | +------+-+---------+ +--------^---------+ +--------^-------+ @@ -246,14 +244,14 @@ reserved:: | | 9 create vfio_ap-passthrough | | | +------------------------------+ | +-------------------------------------------------------------+ - 10 assign adapter/domain/control domain + 12 assign adapter/domain/control domain The process for reserving an AP queue for use by a KVM guest is: 1. The administrator loads the vfio_ap device driver 2. The vfio-ap driver during its initialization will register a single 'matrix' device with the device core. This will serve as the parent device for - all mediated matrix devices used to configure an AP matrix for a guest. + all vfio_ap mediated devices used to configure an AP matrix for a guest. 3. The /sys/devices/vfio_ap/matrix device is created by the device core 4. The vfio_ap device driver will register with the AP bus for AP queue devices of type 10 and higher (CEX4 and newer). The driver will provide the vfio_ap @@ -269,24 +267,24 @@ The process for reserving an AP queue for use by a KVM guest is: default zcrypt cex4queue driver. 8. The AP bus probes the vfio_ap device driver to bind the queues reserved for it. -9. The administrator creates a passthrough type mediated matrix device to be +9. The administrator creates a passthrough type vfio_ap mediated device to be used by a guest 10. The administrator assigns the adapters, usage domains and control domains to be exclusively used by a guest. Set up the VFIO mediated device interfaces ------------------------------------------ -The VFIO AP device driver utilizes the common interface of the VFIO mediated +The VFIO AP device driver utilizes the common interfaces of the VFIO mediated device core driver to: -* Register an AP mediated bus driver to add a mediated matrix device to and +* Register an AP mediated bus driver to add a vfio_ap mediated device to and remove it from a VFIO group. -* Create and destroy a mediated matrix device -* Add a mediated matrix device to and remove it from the AP mediated bus driver -* Add a mediated matrix device to and remove it from an IOMMU group +* Create and destroy a vfio_ap mediated device +* Add a vfio_ap mediated device to and remove it from the AP mediated bus driver +* Add a vfio_ap mediated device to and remove it from an IOMMU group The following high-level block diagram shows the main components and interfaces -of the VFIO AP mediated matrix device driver:: +of the VFIO AP mediated device driver:: +-------------+ | | @@ -343,7 +341,7 @@ matrix device. * device_api: the mediated device type's API * available_instances: - the number of mediated matrix passthrough devices + the number of vfio_ap mediated passthrough devices that can be created * device_api: specifies the VFIO API @@ -351,29 +349,37 @@ matrix device. This attribute group identifies the user-defined sysfs attributes of the mediated device. When a device is registered with the VFIO mediated device framework, the sysfs attribute files identified in the 'mdev_attr_groups' - structure will be created in the mediated matrix device's directory. The - sysfs attributes for a mediated matrix device are: + structure will be created in the vfio_ap mediated device's directory. The + sysfs attributes for a vfio_ap mediated device are: assign_adapter / unassign_adapter: Write-only attributes for assigning/unassigning an AP adapter to/from the - mediated matrix device. To assign/unassign an adapter, the APID of the - adapter is echoed to the respective attribute file. + vfio_ap mediated device. To assign/unassign an adapter, the APID of the + adapter is echoed into the respective attribute file. assign_domain / unassign_domain: Write-only attributes for assigning/unassigning an AP usage domain to/from - the mediated matrix device. To assign/unassign a domain, the domain - number of the usage domain is echoed to the respective attribute + the vfio_ap mediated device. To assign/unassign a domain, the domain + number of the usage domain is echoed into the respective attribute file. matrix: - A read-only file for displaying the APQNs derived from the cross product - of the adapter and domain numbers assigned to the mediated matrix device. + A read-only file for displaying the APQNs derived from the Cartesian + product of the adapter and domain numbers assigned to the vfio_ap mediated + device. + guest_matrix: + A read-only file for displaying the APQNs derived from the Cartesian + product of the adapter and domain numbers assigned to the APM and AQM + fields respectively of the KVM guest's CRYCB. This may differ from the + the APQNs assigned to the vfio_ap mediated device if any APQN does not + reference a queue device bound to the vfio_ap device driver (i.e., the + queue is not in the host's AP configuration). assign_control_domain / unassign_control_domain: Write-only attributes for assigning/unassigning an AP control domain - to/from the mediated matrix device. To assign/unassign a control domain, - the ID of the domain to be assigned/unassigned is echoed to the respective - attribute file. + to/from the vfio_ap mediated device. To assign/unassign a control domain, + the ID of the domain to be assigned/unassigned is echoed into the + respective attribute file. control_domains: A read-only file for displaying the control domain numbers assigned to the - mediated matrix device. + vfio_ap mediated device. * functions: @@ -383,45 +389,75 @@ matrix device. * Store the reference to the KVM structure for the guest using the mdev * Store the AP matrix configuration for the adapters, domains, and control domains assigned via the corresponding sysfs attributes files + * Store the AP matrix configuration for the adapters, domains and control + domains available to a guest. A guest may not be provided access to APQNs + referencing queue devices that do not exist, or are not bound to the + vfio_ap device driver. remove: - deallocates the mediated matrix device's ap_matrix_mdev structure. This will - be allowed only if a running guest is not using the mdev. + deallocates the vfio_ap mediated device's ap_matrix_mdev structure. + This will be allowed only if a running guest is not using the mdev. * callback interfaces - open: + open_device: The vfio_ap driver uses this callback to register a - VFIO_GROUP_NOTIFY_SET_KVM notifier callback function for the mdev matrix - device. The open is invoked when QEMU connects the VFIO iommu group - for the mdev matrix device to the MDEV bus. Access to the KVM structure used - to configure the KVM guest is provided via this callback. The KVM structure, - is used to configure the guest's access to the AP matrix defined via the - mediated matrix device's sysfs attribute files. - release: + VFIO_GROUP_NOTIFY_SET_KVM notifier callback function for the matrix mdev + devices. The open_device callback is invoked by userspace to connect the + VFIO iommu group for the matrix mdev device to the MDEV bus. Access to the + KVM structure used to configure the KVM guest is provided via this callback. + The KVM structure, is used to configure the guest's access to the AP matrix + defined via the vfio_ap mediated device's sysfs attribute files. + + close_device: unregisters the VFIO_GROUP_NOTIFY_SET_KVM notifier callback function for the - mdev matrix device and deconfigures the guest's AP matrix. + matrix mdev device and deconfigures the guest's AP matrix. -Configure the APM, AQM and ADM in the CRYCB -------------------------------------------- -Configuring the AP matrix for a KVM guest will be performed when the + ioctl: + this callback handles the VFIO_DEVICE_GET_INFO and VFIO_DEVICE_RESET ioctls + defined by the vfio framework. + +Configure the guest's AP resources +---------------------------------- +Configuring the AP resources for a KVM guest will be performed when the VFIO_GROUP_NOTIFY_SET_KVM notifier callback is invoked. The notifier -function is called when QEMU connects to KVM. The guest's AP matrix is -configured via it's CRYCB by: +function is called when userspace connects to KVM. The guest's AP resources are +configured via it's APCB by: * Setting the bits in the APM corresponding to the APIDs assigned to the - mediated matrix device via its 'assign_adapter' interface. + vfio_ap mediated device via its 'assign_adapter' interface. * Setting the bits in the AQM corresponding to the domains assigned to the - mediated matrix device via its 'assign_domain' interface. + vfio_ap mediated device via its 'assign_domain' interface. * Setting the bits in the ADM corresponding to the domain dIDs assigned to the - mediated matrix device via its 'assign_control_domains' interface. + vfio_ap mediated device via its 'assign_control_domains' interface. + +The linux device model precludes passing a device through to a KVM guest that +is not bound to the device driver facilitating its pass-through. Consequently, +an APQN that does not reference a queue device bound to the vfio_ap device +driver will not be assigned to a KVM guest's matrix. The AP architecture, +however, does not provide a means to filter individual APQNs from the guest's +matrix, so the adapters, domains and control domains assigned to vfio_ap +mediated device via its sysfs 'assign_adapter', 'assign_domain' and +'assign_control_domain' interfaces will be filtered before providing the AP +configuration to a guest: + +* The APIDs of the adapters, the APQIs of the domains and the domain numbers of + the control domains assigned to the matrix mdev that are not also assigned to + the host's AP configuration will be filtered. + +* Each APQN derived from the Cartesian product of the APIDs and APQIs assigned + to the vfio_ap mdev is examined and if any one of them does not reference a + queue device bound to the vfio_ap device driver, the adapter will not be + plugged into the guest (i.e., the bit corresponding to its APID will not be + set in the APM of the guest's APCB). The CPU model features for AP ----------------------------- -The AP stack relies on the presence of the AP instructions as well as two -facilities: The AP Facilities Test (APFT) facility; and the AP Query -Configuration Information (QCI) facility. These features/facilities are made -available to a KVM guest via the following CPU model features: +The AP stack relies on the presence of the AP instructions as well as three +facilities: The AP Facilities Test (APFT) facility; the AP Query +Configuration Information (QCI) facility; and the AP Queue Interruption Control +facility. These features/facilities are made available to a KVM guest via the +following CPU model features: 1. ap: Indicates whether the AP instructions are installed on the guest. This feature will be enabled by KVM only if the AP instructions are installed @@ -435,24 +471,28 @@ available to a KVM guest via the following CPU model features: can be made available to the guest only if it is available on the host (i.e., facility bit 12 is set). +4. apqi: Indicates AP Queue Interruption Control faclity is available on the + guest. This facility can be made available to the guest only if it is + available on the host (i.e., facility bit 65 is set). + Note: If the user chooses to specify a CPU model different than the 'host' model to QEMU, the CPU model features and facilities need to be turned on explicitly; for example:: - /usr/bin/qemu-system-s390x ... -cpu z13,ap=on,apqci=on,apft=on + /usr/bin/qemu-system-s390x ... -cpu z13,ap=on,apqci=on,apft=on,apqi=on A guest can be precluded from using AP features/facilities by turning them off explicitly; for example:: - /usr/bin/qemu-system-s390x ... -cpu host,ap=off,apqci=off,apft=off + /usr/bin/qemu-system-s390x ... -cpu host,ap=off,apqci=off,apft=off,apqi=off Note: If the APFT facility is turned off (apft=off) for the guest, the guest -will not see any AP devices. The zcrypt device drivers that register for type 10 -and newer AP devices - i.e., the cex4card and cex4queue device drivers - need -the APFT facility to ascertain the facilities installed on a given AP device. If -the APFT facility is not installed on the guest, then the probe of device -drivers will fail since only type 10 and newer devices can be configured for -guest use. +will not see any AP devices. The zcrypt device drivers on the guest that +register for type 10 and newer AP devices - i.e., the cex4card and cex4queue +device drivers - need the APFT facility to ascertain the facilities installed on +a given AP device. If the APFT facility is not installed on the guest, then no +adapter or domain devices will get created by the AP bus running on the +guest because only type 10 and newer devices can be configured for guest use. Example ======= @@ -471,7 +511,7 @@ CARD.DOMAIN TYPE MODE 05.00ab CEX5C CCA-Coproc 06 CEX5A Accelerator 06.0004 CEX5A Accelerator -06.00ab CEX5C CCA-Coproc +06.00ab CEX5A Accelerator =========== ===== ============ Guest2 @@ -479,9 +519,9 @@ Guest2 =========== ===== ============ CARD.DOMAIN TYPE MODE =========== ===== ============ -05 CEX5A Accelerator -05.0047 CEX5A Accelerator -05.00ff CEX5A Accelerator +05 CEX5C CCA-Coproc +05.0047 CEX5C CCA-Coproc +05.00ff CEX5C CCA-Coproc =========== ===== ============ Guest3 @@ -529,40 +569,56 @@ These are the steps: 2. Secure the AP queues to be used by the three guests so that the host can not access them. To secure them, there are two sysfs files that specify - bitmasks marking a subset of the APQN range as 'usable by the default AP - queue device drivers' or 'not usable by the default device drivers' and thus - available for use by the vfio_ap device driver'. The location of the sysfs - files containing the masks are:: + bitmasks marking a subset of the APQN range as usable only by the default AP + queue device drivers. All remaining APQNs are available for use by + any other device driver. The vfio_ap device driver is currently the only + non-default device driver. The location of the sysfs files containing the + masks are:: /sys/bus/ap/apmask /sys/bus/ap/aqmask The 'apmask' is a 256-bit mask that identifies a set of AP adapter IDs - (APID). Each bit in the mask, from left to right (i.e., from most significant - to least significant bit in big endian order), corresponds to an APID from - 0-255. If a bit is set, the APID is marked as usable only by the default AP - queue device drivers; otherwise, the APID is usable by the vfio_ap - device driver. + (APID). Each bit in the mask, from left to right, corresponds to an APID from + 0-255. If a bit is set, the APID belongs to the subset of APQNs marked as + available only to the default AP queue device drivers. The 'aqmask' is a 256-bit mask that identifies a set of AP queue indexes - (APQI). Each bit in the mask, from left to right (i.e., from most significant - to least significant bit in big endian order), corresponds to an APQI from - 0-255. If a bit is set, the APQI is marked as usable only by the default AP |