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qemu-e2k/docs/vfio-ap.txt

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Adjunct Processor (AP) Device
=============================
Contents:
=========
* Introduction
* AP Architectural Overview
* Start Interpretive Execution (SIE) Instruction
* AP Matrix Configuration on Linux Host
* Starting a Linux Guest Configured with an AP Matrix
* Example: Configure AP Matrices for Three 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 depending
on the machine model. 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; however, the maximum adapter number allowed is
determined by machine model. 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; however, the maximum domain number allowed is
determined by machine model. 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.
* 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
AP instructions identify the domain that is targeted to process the AP
command; this must be one of the usage domains. An AP command may modify a
domain that is not one of the usage domains, but the modified domain
must be one of the control domains.
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 satellite control block called
the 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 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,
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, 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.
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: Valid configuration:
------------------------------
Guest1: adapters 1,2 domains 5,6
Guest2: adapters 3,4 domains 5,6
This is also valid because both guests have a unique set of APQNs:
Guest1 has APQNs (1,5), (1,6), (2,5), (2,6);
Guest2 has APQNs (3,5), (3,6), (4,5), (4,6)
Example 3: 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 Matrix 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 via its Activation Profile which can be edited on the HMC. When the
linux system is started, the AP bus will detect the AP devices assigned to the
LPAR and create the following in sysfs:
/sys/bus/ap
... [devices]
...... xx.yyyy
...... ...
...... cardxx
...... ...
Where:
cardxx is AP adapter number xx (in hex)
....xx.yyyy is an APQN with xx specifying the APID and yyyy specifying the
APQI
For example, if AP adapters 5 and 6 and domains 4, 71 (0x47), 171 (0xab) and
255 (0xff) are configured for the LPAR, the sysfs representation on the linux
host system would look like this:
/sys/bus/ap
... [devices]
...... 05.0004
...... 05.0047
...... 05.00ab
...... 05.00ff
...... 06.0004
...... 06.0047
...... 06.00ab
...... 06.00ff
...... card05
...... card06
A set of default device drivers are also created to control each type of AP
device that can be assigned to the LPAR on which a linux host is running:
/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
Binding AP devices to device drivers
------------------------------------
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 alternate device
driver(s). The sysfs locations of 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.
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
queue device drivers; otherwise, the APQI is usable by the vfio_ap device
driver.
Take, for example, the following mask:
0x7dffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
It indicates:
1, 2, 3, 4, 5, and 7-255 belong to the default drivers' pool, and 0 and 6
belong to the vfio_ap device driver's pool.
The APQN of each AP queue device assigned to the linux host is checked by the
AP bus against the set of APQNs derived from the cross product of APIDs
and APQIs marked as usable only by the default AP queue device drivers. If a
match is detected, only the default AP queue device drivers will be probed;
otherwise, the vfio_ap device driver will be probed.
By default, the two masks are set to reserve all APQNs for use by the default
AP queue device drivers. There are two ways the default masks can be changed:
1. The sysfs mask files can be edited by echoing a string into the
respective sysfs mask file in one of two formats:
* An absolute hex string starting with 0x - like "0x12345678" - sets
the mask. If the given string is shorter than the mask, it is padded
with 0s on the right; for example, specifying a mask value of 0x41 is
the same as specifying:
0x4100000000000000000000000000000000000000000000000000000000000000
Keep in mind that the mask reads from left to right (i.e., most
significant to least significant bit in big endian order), so the mask
above identifies device numbers 1 and 7 (01000001).
If the string is longer than the mask, the operation is terminated with
an error (EINVAL).
* Individual bits in the mask can be switched on and off by specifying
each bit number to be switched in a comma separated list. Each bit
number string must be prepended with a ('+') or minus ('-') to indicate
the corresponding bit is to be switched on ('+') or off ('-'). Some
valid values are:
"+0" switches bit 0 on
"-13" switches bit 13 off
"+0x41" switches bit 65 on
"-0xff" switches bit 255 off
The following example:
+0,-6,+0x47,-0xf0
Switches bits 0 and 71 (0x47) on
Switches bits 6 and 240 (0xf0) off
Note that the bits not specified in the list remain as they were before
the operation.
2. The masks can also be changed at boot time via parameters on the kernel
command line like this:
ap.apmask=0xffff ap.aqmask=0x40
This would create the following masks:
apmask:
0xffff000000000000000000000000000000000000000000000000000000000000
aqmask:
0x4000000000000000000000000000000000000000000000000000000000000000
Resulting in these two pools:
default drivers pool: adapter 0-15, domain 1
alternate drivers pool: adapter 16-255, domains 0, 2-255
Configuring an AP matrix for a linux guest.
------------------------------------------
The sysfs interfaces for configuring an AP matrix for a guest 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. When the vfio_ap device driver is loaded, it registers with the VFIO
mediated device framework. When the driver registers, the sysfs interfaces for
creating mediated matrix devices is created:
/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
or
echo $uuid > create
When a mediated AP matrix device is created, a sysfs directory named after
the UUID is created in the 'devices' subdirectory:
/sys/devices
... [vfio_ap]
......[matrix]
......... [mdev_supported_types]
............ [vfio_ap-passthrough]
............... create
............... [devices]
.................. [$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
to the '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, hexadecimal, or octal number. For example, to assign adapters
4, 5 and 16 to a mediated matrix device in decimal, hexadecimal and octal
respectively:
echo 4 > assign_adapter
echo 0x5 > assign_adapter
echo 020 > assign_adapter
In order to successfully assign an adapter:
* The adapter number specified must represent a value from 0 up to the
maximum adapter number allowed by the machine model. If an adapter number
higher than the maximum is specified, the operation will terminate with
an error (ENODEV).
* All APQNs that can be derived from the adapter ID being assigned and the
IDs of the previously assigned domains must be bound to the vfio_ap device
driver. If no domains have yet been assigned, then there must be at least
one APQN with the specified APID bound to the vfio_ap driver. If no such
APQNs are bound to the driver, the operation will terminate with an
error (EADDRNOTAVAIL).
No APQN that can be derived from the adapter ID and the IDs of the
previously assigned domains can be assigned to another mediated matrix
device. If an APQN is assigned to another mediated matrix device, the
operation will terminate with an error (EADDRINUSE).
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 domain number is written into the
'assign_domain' file. This may be done multiple times to assign more than one
usage domain. The domain number is specified using conventional semantics as
a decimal, hexadecimal, or octal number. For example, to assign usage domains
4, 8, and 71 to a mediated matrix device in decimal, hexadecimal and octal
respectively:
echo 4 > assign_domain
echo 0x8 > assign_domain
echo 0107 > assign_domain
In order to successfully assign a domain:
* The domain number specified must represent a value from 0 up to the
maximum domain number allowed by the machine model. If a domain number
higher than the maximum is specified, the operation will terminate with
an error (ENODEV).
* All APQNs that can be derived from the domain ID being assigned and the IDs
of the previously assigned adapters must be bound to the vfio_ap device
driver. If no domains have yet been assigned, then there must be at least
one APQN with the specified APQI bound to the vfio_ap driver. If no such
APQNs are bound to the driver, the operation will terminate with an
error (EADDRNOTAVAIL).
No APQN that can be derived from the domain ID being assigned and the IDs
of the previously assigned adapters can be assigned to another mediated
matrix device. If an APQN is assigned to another mediated matrix device,
the operation will terminate with an error (EADDRINUSE).
unassign_domain
To unassign a usage domain, 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, hexadecimal, or octal number. For
example, to assign control domains 4, 8, and 71 to a mediated matrix device
in decimal, hexadecimal and octal respectively:
echo 4 > assign_domain
echo 0x8 > assign_domain
echo 0107 > assign_domain
In order to successfully assign a control domain, the domain number
specified must represent a value from 0 up to the maximum domain number
allowed by the machine model. If a control domain number higher than the
maximum is specified, the operation will terminate with an error (ENODEV).
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 no changes to the AP matrix will be allowed while a guest using
the mediated matrix device is running. Attempts to assign an adapter,
domain or control domain will be rejected and an error (EBUSY) returned.
Starting a Linux Guest Configured with an AP Matrix:
===================================================
To provide a mediated matrix device for use by a guest, 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 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
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 cross product of the AP
adapter numbers (APID) and queue indexes (APQI) specified in the APM and AQM
fields of the guests's CRYCB respectively. These APQNs identify the AP queues
that are valid for use by the guest; meaning, AP commands can be sent by the
guest to any of these queues for processing.
2. Have authorization to process AP commands to change a control domain
identified in the ADM field of the guest's CRYCB. The AP command must be sent
to a valid APQN (see 1 above).
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 exposed for use only if the AP facilities
are installed on the host system. 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:
$model is the CPU model defined for the guest (defaults to the model of
the host system if not specified).
ap=on|off indicates whether AP facilities are installed (on) or not
(off). The default for CPU models zEC12 or newer
is ap=on. AP facilities must be installed on the guest if a
vfio-ap device (-device vfio-ap,sysfsdev=$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 available
only if the QCI facility is installed on the host system. 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 available
only if the APFT facility is installed on the host system. 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 Three 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
three 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 (5,4), (5,171), (6,4), (6,171),
Guest3
------
CARD.DOMAIN TYPE MODE
------------------------------
06 CEX5A Accelerator
06.0047 CEX5A Accelerator
06.00ff CEX5A Accelerator
These are the steps:
1. Install the vfio_ap module on the linux host. The dependency chain for the
vfio_ap module is:
* iommu
* s390
* zcrypt
* vfio
* vfio_mdev
* vfio_mdev_device
* KVM
To build the vfio_ap module, the kernel build must be configured with the
following Kconfig elements selected:
* IOMMU_SUPPORT
* S390
* ZCRYPT
* S390_AP_IOMMU
* VFIO
* VFIO_MDEV
* VFIO_MDEV_DEVICE
* KVM
If using make menuconfig select the following to build the vfio_ap module:
-> Device Drivers
-> IOMMU Hardware Support
select S390 AP IOMMU Support
-> VFIO Non-Privileged userspace driver framework
-> Mediated device driver frramework
-> VFIO driver for Mediated devices
-> I/O subsystem
-> VFIO support for AP devices
2. Secure the AP queues to be used by the three guests so that the host can not
access them. To secure the AP queues 05.0004, 05.0047, 05.00ab, 05.00ff,
06.0004, 06.0047, 06.00ab, and 06.00ff for use by the vfio_ap device driver,
the corresponding APQNs must be removed from the default queue drivers pool
as follows:
echo -5,-6 > /sys/bus/ap/apmask
echo -4,-0x47,-0xab,-0xff > /sys/bus/ap/aqmask
This will result in AP queues 05.0004, 05.0047, 05.00ab, 05.00ff, 06.0004,
06.0047, 06.00ab, and 06.00ff getting bound to the vfio_ap device driver. The
sysfs directory for the vfio_ap device driver will now contain symbolic links
to the AP queue devices bound to it:
/sys/bus/ap
... [drivers]
...... [vfio_ap]
......... [05.0004]
......... [05.0047]
......... [05.00ab]
......... [05.00ff]
......... [06.0004]
......... [06.0047]
......... [06.00ab]
......... [06.00ff]
Keep in mind that only type 10 and newer adapters (i.e., CEX4 and later)
can be bound to the vfio_ap device driver. The reason for this is to
simplify the implementation by not needlessly complicating the design by
supporting older devices that will go out of service in the relatively near
future, and for which there are few older systems on which to test.
The administrator, therefore, must take care to secure only AP queues that
can be bound to the vfio_ap device driver. The device type for a given AP
queue device can be read from the parent card's sysfs directory. For example,
to see the hardware type of the queue 05.0004:
cat /sys/bus/ap/devices/card05/hwtype
The hwtype must be 10 or higher (CEX4 or newer) in order to be bound to the
vfio_ap device driver.
3. Create the mediated devices needed to configure the AP matrixes for the
three guests and to provide an interface to the vfio_ap driver for
use by the guests:
/sys/devices/vfio_ap/matrix/
--- [mdev_supported_types]
------ [vfio_ap-passthrough] (passthrough mediated matrix device type)
--------- create
--------- [devices]
To create the mediated devices for the three guests:
uuidgen > create
uuidgen > create
uuidgen > create
or
echo $uuid1 > create
echo $uuid2 > create
echo $uuid3 > create
This will create three mediated devices in the [devices] subdirectory named
after the UUID used to create the mediated device. We'll call them $uuid1,
$uuid2 and $uuid3 and this is the sysfs directory structure after creation:
/sys/devices/vfio_ap/matrix/
--- [mdev_supported_types]
------ [vfio_ap-passthrough]
--------- [devices]
------------ [$uuid1]
--------------- assign_adapter
--------------- assign_control_domain
--------------- assign_domain
--------------- matrix
--------------- unassign_adapter
--------------- unassign_control_domain
--------------- unassign_domain
------------ [$uuid2]
--------------- assign_adapter
--------------- assign_control_domain
--------------- assign_domain
--------------- matrix
--------------- unassign_adapter
----------------unassign_control_domain
----------------unassign_domain
------------ [$uuid3]
--------------- 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 the mediated
devices $uuid1 (for Guest1), $uuid2 (for Guest2) and $uuid3 (for Guest3).
This is how the matrix is configured for Guest1:
echo 5 > assign_adapter
echo 6 > assign_adapter
echo 4 > assign_domain
echo 0xab > assign_domain
Control domains can similarly be assigned using the assign_control_domain
sysfs file.
If a mistake is made configuring an adapter, domain or control domain,
you can use the unassign_xxx interfaces to unassign the adapter, domain or
control domain.
To display the matrix configuration for Guest1:
cat matrix
The output will display the APQNs in the format xx.yyyy, where xx is
the adapter number and yyyy is the domain number. The output for Guest1
will look like this:
05.0004
05.00ab
06.0004
06.00ab
This is how the matrix is configured for Guest2:
echo 5 > assign_adapter
echo 0x47 > assign_domain
echo 0xff > assign_domain
This is how the matrix is configured for Guest3:
echo 6 > assign_adapter
echo 0x47 > assign_domain
echo 0xff > assign_domain
5. Start Guest1:
/usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on \
-device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid1 ...
7. Start Guest2:
/usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on \
-device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid2 ...
7. Start Guest3:
/usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on \
-device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid3 ...
When the guest is shut down, the mediated matrix devices may be removed.
Using our example again, to remove the mediated matrix device $uuid1:
/sys/devices/vfio_ap/matrix/
--- [mdev_supported_types]
------ [vfio_ap-passthrough]
--------- [devices]
------------ [$uuid1]
--------------- remove
echo 1 > remove
This will remove all of the mdev matrix device's sysfs structures including
the mdev device itself. To recreate and reconfigure the mdev matrix device,
all of the steps starting with step 3 will have to be performed again. Note
that the remove will fail if a guest using the mdev is still running.
It is not necessary to remove an mdev matrix device, but one may want to
remove it if no guest will use it during the remaining lifetime of the linux
host. If the mdev matrix device is removed, one may want to also reconfigure
the pool of adapters and queues reserved for use by the default drivers.
Limitations
===========
* The KVM/kernel interfaces do not provide a way to prevent restoring an APQN
to the default drivers pool of a queue that is still assigned to a mediated
device in use by a guest. It is incumbent upon the administrator to
ensure there is no mediated device in use by a guest to which the APQN is
assigned lest the host be given access to the private data of the AP queue
device, such as a private key configured specifically for the guest.
* Dynamically modifying the AP matrix for a running guest (which would amount to
hot(un)plug of AP devices for the guest) is currently not supported
* Live guest migration is not supported for guests using AP devices.
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