[Qemu-devel] [PATCH v4 5/5] s390: doc: detailed specifications for AP virtualization

[Tony Krowiak]

This patch provides documentation describing the AP architecture and
design concepts behind the virtualization of AP devices. It also
includes an example of how to configure AP devices for exclusive
use of KVM guests.

Signed-off-by: Tony Krowiak <address@hidden>
---
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+Adjunct Processor (AP) Device
+=============================
+
+Contents:
+=========
+* Introduction
+* AP Architectural Overview
+* Start Interpretive Execution (SIE) Instruction
+* AP Matrix Configuration on Linux Host
+* AP Matrix Configuration for a Linux Guest
+* Starting a Linux Guest Configured with an AP Matrix
+* Example: Configure AP Matrices for Two Linux Guests
+
+Introduction:
+============
+The IBM Adjunct Processor (AP) Cryptographic Facility is comprised
+of three AP instructions and from 1 to 256 PCIe cryptographic adapter cards.
+These AP devices provide cryptographic functions to all CPUs assigned to a
+linux system running in an IBM Z system LPAR.
+
+On s390x, AP adapter cards are exposed via the AP bus. This document
+describes how those cards may be made available to KVM guests using the
+VFIO mediated device framework.
+
+AP Architectural Overview:
+=========================
+In order understand the terminology used in the rest of this document, let's
+start with some definitions:
+
+* AP adapter
+
+  An AP adapter is an IBM Z adapter card that can perform cryptographic
+  functions. There can be from 0 to 256 adapters assigned to an LPAR. Adapters
+  assigned to the LPAR in which a linux host is running will be available to
+  the linux host. Each adapter is identified by a number from 0 to 255. When
+  installed, an AP adapter is accessed by AP instructions executed by any CPU.
+
+* AP domain
+
+  An adapter is partitioned into domains. Each domain can be thought of as
+  a set of hardware registers for processing AP instructions. An adapter can
+  hold up to 256 domains. Each domain is identified by a number from 0 to 255.
+  Domains can be further classified into two types:
+
+    * Usage domains are domains that can be accessed directly to process AP
+      commands
+
+    * Control domains are domains that are accessed indirectly by AP
+      commands sent to a usage domain to control or change the domain, for
+      example; to set a secure private key for the domain.
+
+  The AP usage and control domains are assigned to a given LPAR via the 
system's
+  Activation Profile which can be edited via the HMC. When the system is IPL'd,
+  the AP bus module is loaded and detects the AP usage and control domains
+  assigned to the LPAR. The domain number of each usage domain will be coupled
+  with the adapter number of each AP adapter assigned to the LPAR to identify
+  the AP queues (see AP Queue section below). The domain number of each control
+  domain will be represented in a bitmask and stored in a sysfs file
+  /sys/bus/ap/ap_control_domain_mask created by the bus. The bits in the mask,
+  from most to least significant bit, correspond to domains 0-255.
+
+  A domain may be assigned to a system as both a usage and control domain, or
+  as a control domain only. Consequently, all domains assigned as both a usage
+  and control domain can both process AP commands as well as be changed by an 
AP
+  command sent to any usage domain assigned to the same system. Domains 
assigned
+  only as control domains can not process AP commands but can be changed by AP
+  commands sent to any usage domain assigned to the system.
+
+* AP Queue
+
+  An AP queue is the means by which an AP command-request message is sent to an
+  AP usage domain inside a specific AP. An AP queue is identified by a tuple
+  comprised of an AP adapter ID (APID) and an AP queue index (APQI). The
+  APQI corresponds to a given usage domain number within the adapter. This 
tuple
+  forms an AP Queue Number (APQN) uniquely identifying an AP queue. AP
+  instructions include a field containing the APQN to identify the AP queue to
+  which the AP command-request message is to be sent for processing.
+
+* AP Instructions:
+
+  There are three AP instructions:
+
+  * NQAP: to enqueue an AP command-request message to a queue
+  * DQAP: to dequeue an AP command-reply message from a queue
+  * PQAP: to administer the queues
+
+Start Interpretive Execution (SIE) Instruction
+==============================================
+A KVM guest is started by executing the Start Interpretive Execution (SIE)
+instruction. The SIE state description is a control block that contains the
+state information for a KVM guest and is supplied as input to the SIE
+instruction. The SIE state description contains a field that references
+a Crypto Control Block (CRYCB). The CRYCB contains 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 most significant to least
+  significant bit, 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 most significant to
+  least significant bit, 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 least significant to most significant bit,
+  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
+  configured for the KVM guest.
+
+If you recall from the description of an AP Queue, AP instructions include
+an APQN to identify the AP adapter and 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.
+
+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
+at most one guest or the linux host.
+
+   Example 1: Valid configuration:
+   ------------------------------
+   Guest1: adapters 1,2  domains 5,6
+   Guest2: adapter  1,2  domain 7
+
+   This is valid because both guests have a unique set of APQNs: Guest1 has
+   APQNs (1,5), (1,6), (2,5) and (2,6); Guest2 has APQNs (1,7) and (2,7).
+
+   Example 2: Invalid configuration:
+   --------------------------------
+   Guest1: adapters 1,2  domains 5,6
+   Guest2: adapter  1    domains 6,7
+
+   This is an invalid configuration because both guests have access to
+   APQN (1,6).
+
+AP device Configuration on Linux Host:
+=====================================
+A linux system is a guest of the LPAR in which it is running and has access to
+the AP resources configured for the LPAR. The LPAR's AP matrix is
+configured using the 'Customize/Delete Activation Profiles' dialog from the 
HMC.
+This dialog displays the activation profiles configured for the linux system.
+Selecting the specific activation profile to be edited and clicking the
+'Customize Profile' button will open the 'Customize Image Profiles' dialog.
+Selecting the 'Crypto' link in the tree view on the left hand side of the 
dialog
+will display the AP matrix configuration in the right hand panel. There, one 
can
+assign AP adapters - called Cryptos - and domains to the LPAR. When the linux
+system is started using this activation profile, it will have access to the
+matrix of AP adapters and domains configured via the activation profile.
+
+When the linux system is started, the AP adapter devices will be connected to
+the AP bus and the following AP matrix interfaces will be created in sysfs:
+
+/sys/bus/ap
+... [devices]
+...... xx.yyyy
+...... ...
+...... cardxx
+...... ...
+
+Where:
+    cardxx     is adapter number xx (in hex)
+    yyyy       is a usage domain number yyyy (in hex)
+....xx.yyyy    is APQN (xx,yyyy)
+
+For example, if AP adapters 5 and 6 and domains 4 and 71 (0x47) are configured
+for the LPAR, the sysfs representation on the linux system would look like 
this:
+
+/sys/bus/ap
+... [devices]
+...... 05.0004
+...... 05.0047
+...... 06.0004
+...... 06.0047
+...... card05
+...... card06
+
+There will also be AP device drivers created to control each type of AP matrix
+interface available to the IBM Z system:
+
+/sys/bus/ap
+... [drivers]
+...... [cex2acard]        for Crypto Express 2/3 accelerator cards
+...... [cex2aqueue]       for AP queues served by Crypto Express 2/3
+                          accelerator cards
+...... [cex4card]         for Crypto Express 4/5/6 accelerator and coprocessor
+                          cards
+...... [cex4queue]        for AP queues served by Crypto Express 4/5/6
+                          accelerator and coprocessor cards
+...... [pcixcccard]       for Crypto Express 2/3 coprocessor cards
+...... [pcixccqueue]      for AP queues served by Crypto Express 2/3
+                          coprocessor cards
+
+Links to the AP interfaces controlled by each AP device driver will be created
+in the device driver's sysfs directory. For example, if AP adapter 5 and 
domains
+4 and 71 (0x47) are assigned to the LPAR and adapter 5 is a CEX5 card, the
+following links will be created in the CEX5 drivers' sysfs directories:
+
+/sys/bus/ap
+... [drivers]
+...... [cex4card]
+......... [card05]
+...... [cex4queue]
+......... [05.0004]
+......... [05.0047]
+
+AP Matrix Configuration for a Linux Guest:
+=========================================
+In order to configure the AP matrix for a guest, the adapters, usage domains
+and control domains to be used by the guest must be assigned to the guest. This
+section describes how to configure a guest's AP matrix.
+
+The kernel interfaces for configuring an AP matrix for a linux guest are built
+on the VFIO mediated device framework and are provided by the vfio_ap
+kernel module. By default, the vfio_ap module is a loadable module, The
+dependency chain for the vfio_ap module is:
+* vfio
+* mdev
+* vfio_mdev
+* vfio_ap
+
+When installed, the vfio_ap module is initialized. During module 
initialization,
+a vfio_ap driver is created and registered with the AP bus creating the
+following sysfs interfaces:
+
+ /sys/bus/ap/drivers/
+...[vfio_ap]
+...... bind
+...... unbind
+
+The vfio_ap device driver will create a 'matrix' device to hold the APQNs
+reserved for exclusive use by KVM guests:
+
+/sys/devices/
+... [vfio_ap]
+......[matrix] symlink to the matrix device directory
+
+The vfio_ap device driver serves several purposes:
+1. Provides an interface for securing APQNs preventing their use by the host
+   linux system and reserving their use by one or more guests.
+2. Creates the sysfs interfaces for configuring an AP matrix for a linux guest.
+
+Securing APQNs
+--------------
+   An APQN is reserved by unbinding an AP queue device AP bus device driver and
+   binding it to the vfio_ap device driver. For example, suppose we want to
+   secure APQN (05,0004). Assuming that the AP adapter card 5 is a CEX5
+   coprocessor card:
+
+   echo 05.0004 > /sys/bus/ap/drivers/cex4queue/unbind
+   echo 05.0004 > /sys/bus/ap/drivers/vfio_ap/bind
+
+   This action will store the APQN in the /sys/devices/vfio_ap/matrix device
+   which makes it available for use by a linux guest.
+
+Configuring an AP matrix for a linux guest.
+------------------------------------------
+These sysfs interfaces are built on the VFIO mediated device framework. To
+configure an AP matrix for a guest, a mediated matrix device must first be
+created for the /sys/devices/vfio_ap/matrix device. The sysfs interfaceAPQI 
corresponding to
+for creating a mediated matrix device is in:
+
+/sys/devices
+... [vfio_ap]
+......[matrix]
+......... [mdev_supported_types]
+............ [vfio_ap-passthrough]
+............... create
+............... [devices]
+
+A mediated AP matrix device is created by writing a UUID to the attribute
+file named 'create', for example:
+
+   uuidgen > create
+
+When a mediated AP matrix device is created, a sysfs directory named after
+the UUID:
+
+/sys/devices
+... [vfio_ap]
+......[matrix]
+......... [mdev_supported_types]
+............ [vfio_ap-passthrough]
+............... create
+............... [devices]
+.................. [$uuid]
+
+There will also be three sets of attribute files created in the mediated
+matrix device's sysfs directory to configure an AP matrix for the
+KVM guest:
+
+/sys/devices
+... [vfio_ap]
+......[matrix]
+......... [mdev_supported_types]
+............ [vfio_ap-passthrough]
+............... create
+............... [devices]
+.................. [$uuid]
+..................... assign_adapter
+..................... assign_control_domain
+..................... assign_domain
+..................... matrix
+..................... unassign_adapter
+..................... unassign_control_domain
+..................... unassign_domain
+
+assign_adapter
+   To assign an AP adapter to the mediated matrix device, its APID is written
+   'assign_adapter' file. This may be done multiple times to assign more than
+   one adapter. The APID may be specified using conventional semantics
+   as a decimal, hexidecimal, or octal number. For example, to assign adapters
+   4, 5 and 16 to mediated matrix device $uuid in decimal, hexidecimal and 
octal
+   respectively:
+
+       echo 4 > assign_adapter
+       echo 0x5 > assign_adapter
+       echo 020 > assign_adapter
+
+unassign_adapter
+   To unassign an AP adapter, its APID is written to the 'unassign_adapter'
+   file. This may also be done multiple times to unassign more than one 
adapter.
+
+assign_domain
+   To assign a usage domain, the APQI corresponding to the domain number is
+   written into the 'assign_domain' file. This may be done multiple times to
+   assign more than one usage domain. The APQI may be specified using
+   conventional semantics as a decimal, hexidecimal, or octal number. For
+   example, to assign usage domains 4, 8, and 71 to mediated matrix device
+   $uuid in decimal, hexidecimal and octal respectively:
+
+      echo 4 > assign_domain
+      echo 0x8 > assign_domain
+      echo 0107 > assign_domain
+
+unassign_domain
+   To unassign a usage domain, the APQI corresponding to the domain number is
+   written into the 'unassign_domain' file. This may be done multiple times to
+   unassign more than one usage domain.
+
+assign_control_domain
+   To assign a control domain, the domain number is written into the
+   'assign_control_domain' file. This may be done multiple times to
+   assign more than one control domain. The domain number may be specified 
using
+   conventional semantics as a decimal, hexidecimal, or octal number. For
+   example, to assign  control domains 4, 8, and 71 to mediated matrix device
+   $uuid in decimal, hexidecimal and octal respectively:
+
+      echo 4 > assign_domain
+      echo 0x8 > assign_domain
+      echo 0107 > assign_domain
+
+unassign_control_domain
+   To unassign a control domain, the domain number is written into the
+   'unassign_domain' file. This may be done multiple times to unassign more 
than
+   one control domain.
+
+Notes:
+* Hot plug/unplug is not currently supported for mediated AP matrix devices,
+  so the AP matrix resulting from assignment and/or unassignment of AP
+  adapters, usage domains and control domains to a mediated AP matrix device
+  while the guest is running will not take affect until the linux guest is
+  rebooted.
+* For the initial implementation, all usage domains configured for a KVM guest
+  will also be implicitly assigned as control domains also, to there is no
+  need to assign control domains that are assigned as usage domains. This could
+  change in future releases.
+
+Starting a Linux Guest Configured with an AP Matrix:
+===================================================
+In addition to providing the sysfs interfaces for configuring the AP matrix for
+a linux guest, a mediated matrix device also acts as a communication pathway
+between QEMU and the vfio_ap device driver. To gain access to the
+device driver, the following option must be specified on the QEMU command line:
+
+   -device vfio_ap,sysfsdev=$path-to-mdev
+
+The sysfsdev parameter specifies the path to the mediated matrix device.
+There are a number of ways to specify this path:
+
+/sys/devices/vfio_ap/matrix/$uuid
+/sys/bus/mdev/devices/$uuid
+/sys/bus/mdev/drivers/vfio_mdev/$uuid
+/sys/devices/vfio_ap/matrix/mdev_supported_types/vfio_ap-passthrough/devices/$uuid
+
+When the linux guest is subsequently started, the guest will open the mediated
+matrix device's file descriptor to get information about the mediated matrix
+device. The vfio_ap device driver will update the APM, AQM, and ADM fields in 
the
+guest's CRYCB with the adapter, usage domain and control domains assigned to
+via the mediated matrix device's sysfs attribute files. Programs running on the
+linux guest will then:
+
+1. Have direct access to the APQNs derived from the intersection of the AP
+   adapter and usage domain numbers specified in the APM and AQM respectively
+
+2. Have authorization to process AP commands to change - e.g., store a new
+   secure key - a control domain identified in an AP instruction sent to a 
valid
+   APQN.
+
+CPU model features:
+
+Three CPU model features are available for controlling guest access to AP
+facilities:
+
+1. AP facilities feature
+
+   The AP facilities feature indicates that AP facilities are installed on the
+   guest. This feature will be enabled by the kernel only if the AP facilities
+   are installed on the host system. It will be turned on automatically for
+   guests started with CPU model zEC12 or newer. The feature is s390-specific
+   and is represented as a parameter of the -cpu option on the QEMU command
+   line:
+
+      qemu-system-s390x -cpu $model,ap=on|off
+
+      Where:
+
+         $model is the CPU model defined for the guest (defaults to the model 
of
+                the host system if not specified).
+
+         ap=on|off indicates whether AP facilities are installed (on) or not
+                   (off). The default for CPU models zEC12 or newer
+                   is ap=on. AP facilities must be installed a vfio-ap device
+                   (-device vfio-ap,sysfsdev=$path) is configured for the
+                   guest or the guest will fail to start.
+
+2. Query Configuration Information (QCI) facility
+
+   The QCI facility is used by the AP bus running on the guest to query the
+   configuration of the AP facilities. This facility will be enabled by
+   the kernel only if the QCI facility is installed on the host system. It will
+   be turned on automatically for guests started with CPU model zEC12 or newer.
+   The feature is s390-specific and is represented as a parameter of the -cpu
+   option on the QEMU command line:
+
+      qemu-system-s390x -cpu $model,apqci=on|off
+
+      Where:
+
+         $model is the CPU model defined for the guest
+
+         apqci=on|off indicates whether the QCI facility is installed (on) or
+                      not (off). The default for CPU models zEC12 or newer
+                      is apqci=on; for older models, QCI will not be installed.
+
+                      If QCI is installed (apqci=on) but AP facilities are not
+                      (ap=off), an error message will be logged, but the guest
+                      will be allowed to start. It makes no sense to have QCI
+                      installed if the AP facilities are not; this is 
considered
+                      an invalid configuration.
+
+                      If the QCI facility is not installed, APQNs with an APQI
+                      greater than 15 will not be detected by the AP bus
+                      running on the guest.
+
+3. Adjunct Process Facility Test (APFT) facility
+
+   The APFT facility is used by the AP bus running on the guest to test the
+   AP facilities available for a given AP queue. This facility will be enabled
+   by the kernel only if the APFT facility is installed on the host system. It
+   will be turned on automatically for guests started with CPU model zEC12 or
+   newer. The feature is s390-specific and is represented as a parameter of the
+   -cpu option on the QEMU command line:
+
+      qemu-system-s390x -cpu $model,apft=on|off
+
+      Where:
+
+         $model is the CPU model defined for the guest (defaults to the model 
of
+                the host system if not specified).
+
+         apft=on|off indicates whether the APFT facility is installed (on) or
+                     not (off). The default for CPU models zEC12 and
+                     newer is apft=on for older models, APFT will not be
+                     installed.
+
+                     If APFT is installed (apft=on) but AP facilities are not
+                     (ap=off), an error message will be logged, but the guest
+                     will be allowed to start. It makes no sense to have APFT
+                     installed if the AP facilities are not; this is considered
+                     an invalid configuration.
+
+                     It also makes no sense to turn APFT off because the AP bus
+                     running on the guest will not detect CEX4 and newer 
devices
+                     without it. Since only CEX4 and newer devices are 
supported
+                     for guest usage, no AP devices can be made accessible to a
+                     guest started without APFT installed.
+
+Example: Configure AP Matrixes for Two Linux Guests:
+===================================================
+Let's now provide an example to illustrate how KVM guests may be given
+access to AP facilities. For this example, we will show how to configure
+two guests such that executing the lszcrypt command on the guests would
+look like this:
+
+Guest1
+------
+CARD.DOMAIN TYPE  MODE
+------------------------------
+05          CEX5C CCA-Coproc
+05.0004     CEX5C CCA-Coproc
+05.00ab     CEX5C CCA-Coproc
+06          CEX5A Accelerator
+06.0004     CEX5A Accelerator
+06.00ab     CEX5C CCA-Coproc
+
+Guest2
+------
+CARD.DOMAIN TYPE  MODE
+------------------------------
+05          CEX5A Accelerator
+05.0047     CEX5A Accelerator
+05.00ff     CEX5A Accelerator
+
+These are the steps for configuring the Guest1 and Guest2:
+
+1. The first thing that needs to be done is to secure the AP queues to be
+   used by the two guests so that the host can not access them. This is done
+   by unbinding each AP Queue device from its respective AP driver. In our
+   example, these queues are bound to the cex4queue driver. This would be
+   the sysfs location of these devices:
+
+   /sys/bus/ap
+   --- [drivers]
+   ------ [cex4queue]
+   --------- [05.0004]
+   --------- [05.0047]
+   --------------------- control_domains
+   --------------------- domains
+   --------- [05.00ab]
+   --------- [05.00ff]
+   --------- [06.0004]
+   --------- [06.00ab]
+   --------- unbind
+
+   To unbind AP queue 05.0004 from the cex4queue device driver:
+
+    echo 05.0004 > unbind
+
+   This must also be done for AP queues 05.00ab, 05.0047, 05.00ff, 06.0004,
+   and 06.00ab.
+
+2. The next step is to reserve the queues for use by the two KVM guests.
+   This is accomplished by binding them to the VFIO AP device driver.
+   This is the sysfs location of the VFIO AP device driver:
+
+   /sys/bus/ap
+   ---[drivers]
+   ------ [vfio_ap]
+   ---------- bind
+
+   To bind queue 05.0004 to the vfio_ap driver:
+
+    echo 05.0004 > bind
+
+   This must also be done for AP queues 05.00ab, 05.0047, 05.00ff, 06.0004,
+   and 06.00ab.
+
+3. Create the mediated devices needed to configure the AP matrixes for the
+   two guests and to provide an interface to the vfio_ap driver for
+   use by the guests:
+
+   /sys/devices/
+   --- [vfio_ap]
+   ------ [matrix] (this is the matrix device)
+   --------- [mdev_supported_types]
+   ------------ [vfio_ap-passthrough] (passthrough mediated matrix device type)
+   --------------- create
+   --------------- [devices]
+
+   To create the mediated devices for the two guests:
+
+    uuidgen > create
+    uuidgen > create
+
+   This will create two mediated devices in the [devices] subdirectory named
+   with the UUID written to the create attribute file. We call them $uuid1
+   and $uuid2:
+
+   /sys/devices/
+   --- [vfio_ap]
+   ------ [matrix]
+   --------- [mdev_supported_types]
+   ------------ [vfio_ap-passthrough]
+   --------------- [devices]
+   ------------------ [$uuid1]
+   --------------------- assign_adapter
+   --------------------- assign_control_domain
+   --------------------- assign_domain
+   --------------------- matrix
+   --------------------- unassign_adapter
+   --------------------- unassign_control_domain
+   --------------------- unassign_domain
+
+   ------------------ [$uuid2]
+   --------------------- assign_adapter
+   --------------------- assign_control_domain
+   --------------------- assign_domain
+   --------------------- matrix
+   --------------------- unassign_adapter
+   --------------------- unassign_control_domain
+   --------------------- unassign_domain
+
+4. The administrator now needs to configure the matrixes for mediated
+   devices $uuid1 (for Guest1) and $uuid2 (for Guest2).
+
+   This is how the matrix is configured for Guest1:
+
+   cd $uuid1
+   echo 5 > assign_adapter
+   echo 6 > assign_adapter
+   echo 4 > assign_domain
+   echo 0xab > assign_domain
+
+   For this implementation, all usage domains - i.e., domains assigned
+   via the assign_domain attribute file - will also be configured in the ADM
+   field of the KVM guest's CRYCB, so there is no need to assign control
+   domains here unless you want to assign control domains that are not
+   assigned as usage domains.
+
+   If a mistake is made configuring an adapter, domain or control domain,
+   you can use the unassign_xxx files to unassign the adapter, domain or
+   control domain.
+
+   To display the matrix configuration for Guest1:
+
+   cat matrix
+
+   This is how the matrix is configured for Guest2:
+
+   cd $uuid2
+   echo 5 > assign_adapter
+   echo 0x47 > assign_domain
+   echo 0xff > assign_domain
+
+5. Start Guest1
+
+   /usr/bin/qemu-system-s390x ... -device 
vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid1 ...
+
+6. Start Guest2
+
+   /usr/bin/qemu-system-s390x ... -device 
vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid2 ...
-- 
1.7.1