system/linux
system/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux synced 2024-09-16 09:05:45 +00:00
Code Issues Packages Projects Releases Wiki Activity

s390/vfio-ap: update docs to include dynamic config support

Browse source 
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: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Jason J. Herne <jjherne@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Tony Krowiak 2020-08-17 15:19:44 -04:00 committed by Alexander Gordeev
parent eeb386aeb5
commit cb269e0aba
1 changed files with 347 additions and 147 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

494
Documentation/s390/vfio-ap.rst
View file

@ -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:
unregisters the VFIO_GROUP_NOTIFY_SET_KVM notifier callback function for the
mdev matrix device and deconfigures the guest's AP matrix.
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.
Configure the APM, AQM and ADM in the CRYCB
-------------------------------------------
Configuring the AP matrix for a KVM guest will be performed when the
close_device:
unregisters the VFIO_GROUP_NOTIFY_SET_KVM notifier callback function for the
matrix mdev device and deconfigures the guest's AP matrix.
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
queue device drivers; otherwise, the APQI is usable by the vfio_ap device
driver.
(APQI). Each bit in the mask, from left to right, corresponds to an APQI from
0-255. If a bit is set, the APQI belongs to the subset of APQNs marked as
available only to the default AP queue device drivers.
Take, for example, the following mask::
The Cartesian product of the APIDs corresponding to the bits set in the
apmask and the APQIs corresponding to the bits set in the aqmask comprise
the subset of APQNs that can be used only by the host default device drivers.
All other APQNs are available to the non-default device drivers such as the
vfio_ap driver.
0x7dffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
Take, for example, the following masks::
It indicates:
apmask:
0x7d00000000000000000000000000000000000000000000000000000000000000
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.
aqmask:
0x8000000000000000000000000000000000000000000000000000000000000000
The masks indicate:
* Adapters 1, 2, 3, 4, 5, and 7 are available for use by the host default
device drivers.
* Domain 0 is available for use by the host default device drivers
* The subset of APQNs available for use only by the default host device
drivers are:
(1,0), (2,0), (3,0), (4.0), (5,0) and (7,0)
* All other APQNs are available for use by the non-default device drivers.
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
AP bus against the set of APQNs derived from the Cartesian product of APIDs
and APQIs marked as available to 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.
@ -579,8 +635,7 @@ These are the steps:
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
Keep in mind that the mask reads from left to right, so the mask
above identifies device numbers 1 and 7 (01000001).
If the string is longer than the mask, the operation is terminated with
@ -626,11 +681,22 @@ These are the steps:
default drivers pool: adapter 0-15, domain 1
alternate drivers pool: adapter 16-255, domains 0, 2-255
Note ***:
Changing a mask such that one or more APQNs will be taken from a vfio_ap
mediated device (see below) will fail with an error (EBUSY). A message
is logged to the kernel ring buffer which can be viewed with the 'dmesg'
command. The output identifies each APQN flagged as 'in use' and identifies
the vfio_ap mediated device to which it is assigned; for example:
Userspace may not re-assign queue 05.0054 already assigned to 62177883-f1bb-47f0-914d-32a22e3a8804
Userspace may not re-assign queue 04.0054 already assigned to cef03c3c-903d-4ecc-9a83-40694cb8aee4
Securing the APQNs for our example
----------------------------------
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 can either be removed from the default masks::
APQNs can be removed from the default masks using either of the following
commands::
echo -5,-6 > /sys/bus/ap/apmask
@ -683,7 +749,7 @@ Securing the APQNs for our example
/sys/devices/vfio_ap/matrix/
--- [mdev_supported_types]
------ [vfio_ap-passthrough] (passthrough mediated matrix device type)
------ [vfio_ap-passthrough] (passthrough vfio_ap mediated device type)
--------- create
--------- [devices]
@ -734,6 +800,9 @@ Securing the APQNs for our example
----------------unassign_control_domain
----------------unassign_domain
Note *****: The vfio_ap mdevs do not persist across reboots unless the
mdevctl tool is used to create and persist them.
4. The administrator now needs to configure the matrixes for the mediated
devices $uuid1 (for Guest1), $uuid2 (for Guest2) and $uuid3 (for Guest3).
@ -755,6 +824,10 @@ Securing the APQNs for our example
cat matrix
To display the matrix that is or will be assigned to Guest1::
cat guest_matrix
This is how the matrix is configured for Guest2::
echo 5 > assign_adapter
@ -774,17 +847,24 @@ Securing the APQNs for our example
higher than the maximum is specified, the operation will terminate with
an error (ENODEV).
* All APQNs that can be derived from the adapter ID 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).
Note: The maximum adapter number can be obtained via the sysfs
/sys/bus/ap/ap_max_adapter_id attribute file.
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).
* Each APQN derived from the Cartesian product of the APID of the adapter
being assigned and the APQIs of the domains previously assigned:
- Must only be available to the vfio_ap device driver as specified in the
sysfs /sys/bus/ap/apmask and /sys/bus/ap/aqmask attribute files. If even
one APQN is reserved for use by the host device driver, the operation
will terminate with an error (EADDRNOTAVAIL).
- Must NOT be assigned to another vfio_ap mediated device. If even one APQN
is assigned to another vfio_ap mediated device, the operation will
terminate with an error (EBUSY).
- Must NOT be assigned while the sysfs /sys/bus/ap/apmask and
sys/bus/ap/aqmask attribute files are being edited or the operation may
terminate with an error (EBUSY).
In order to successfully assign a domain:
@ -793,41 +873,50 @@ Securing the APQNs for our example
higher than the maximum is specified, the operation will terminate with
an error (ENODEV).
* All APQNs that can be derived from the domain ID 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).
Note: The maximum domain number can be obtained via the sysfs
/sys/bus/ap/ap_max_domain_id attribute file.
No APQN that can be derived from the domain ID 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).
* Each APQN derived from the Cartesian product of the APQI of the domain
being assigned and the APIDs of the adapters previously assigned:
In order to successfully assign a control domain, the domain number
specified must represent a value from 0 up to the maximum domain number
configured for the system. If a control domain number higher than the maximum
is specified, the operation will terminate with an error (ENODEV).
- Must only be available to the vfio_ap device driver as specified in the
sysfs /sys/bus/ap/apmask and /sys/bus/ap/aqmask attribute files. If even
one APQN is reserved for use by the host device driver, the operation
will terminate with an error (EADDRNOTAVAIL).
- Must NOT be assigned to another vfio_ap mediated device. If even one APQN
is assigned to another vfio_ap mediated device, the operation will
terminate with an error (EBUSY).
- Must NOT be assigned while the sysfs /sys/bus/ap/apmask and
sys/bus/ap/aqmask attribute files are being edited or the operation may
terminate with an error (EBUSY).
In order to successfully assign a control domain:
* The domain number specified must represent a value from 0 up to the maximum
domain number configured for the system. If a control domain number higher
than the maximum is specified, the operation will terminate with an
error (ENODEV).
5. Start Guest1::
/usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on \
/usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on,apqi=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 \
/usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on,apqi=on \
-device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid2 ...
7. Start Guest3::
/usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on \
/usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on,apqi=on \
-device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid3 ...
When the guest is shut down, the mediated matrix devices may be removed.
When the guest is shut down, the vfio_ap mediated devices may be removed.
Using our example again, to remove the mediated matrix device $uuid1::
Using our example again, to remove the vfio_ap mediated device $uuid1::
/sys/devices/vfio_ap/matrix/
--- [mdev_supported_types]
@ -840,26 +929,137 @@ Using our example again, to remove the mediated matrix device $uuid1::
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,
This will remove all of the matrix mdev device's sysfs structures including
the mdev device itself. To recreate and reconfigure the matrix mdev 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.
that the remove will fail if a guest using the vfio_ap mdev is still running.
It is not necessary to remove an mdev matrix device, but one may want to
It is not necessary to remove a vfio_ap mdev, 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
host. If the vfio_ap mdev is removed, one may want to also reconfigure
the pool of adapters and queues reserved for use by the default drivers.
Hot plug/unplug support:
================
An adapter, domain or control domain may be hot plugged into a running KVM
guest by assigning it to the vfio_ap mediated device being used by the guest if
the following conditions are met:
* The adapter, domain or control domain must also be assigned to the host's
AP configuration.
* Each APQN derived from the Cartesian product comprised of the APID of the
adapter being assigned and the APQIs of the domains assigned must reference a
queue device bound to the vfio_ap device driver.
* To hot plug a domain, each APQN derived from the Cartesian product
comprised of the APQI of the domain being assigned and the APIDs of the
adapters assigned must reference a queue device bound to the vfio_ap device
driver.
An adapter, domain or control domain may be hot unplugged from a running KVM
guest by unassigning it from the vfio_ap mediated device being used by the
guest.
Over-provisioning of AP queues for a KVM guest:
==============================================
Over-provisioning is defined herein as the assignment of adapters or domains to
a vfio_ap mediated device that do not reference AP devices in the host's AP
configuration. The idea here is that when the adapter or domain becomes
available, it will be automatically hot-plugged into the KVM guest using
the vfio_ap mediated device to which it is assigned as long as each new APQN
resulting from plugging it in references a queue device bound to the vfio_ap
device driver.
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.
Live guest migration is not supported for guests using AP devices without
intervention by a system administrator. Before a KVM guest can be migrated,
the vfio_ap mediated device must be removed. Unfortunately, it can not be
removed manually (i.e., echo 1 > /sys/devices/vfio_ap/matrix/$UUID/remove) while
the mdev is in use by a KVM guest. If the guest is being emulated by QEMU,
its mdev can be hot unplugged from the guest in one of two ways:
* 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
1. If the KVM guest was started with libvirt, you can hot unplug the mdev via
the following commands:
* Live guest migration is not supported for guests using AP devices.
virsh detach-device <guestname> <path-to-device-xml>
For example, to hot unplug mdev 62177883-f1bb-47f0-914d-32a22e3a8804 from
the guest named 'my-guest':
virsh detach-device my-guest ~/config/my-guest-hostdev.xml
The contents of my-guest-hostdev.xml:
<hostdev mode='subsystem' type='mdev' managed='no' model='vfio-ap'>
<source>
<address uuid='62177883-f1bb-47f0-914d-32a22e3a8804'/>
</source>
</hostdev>
virsh qemu-monitor-command <guest-name> --hmp "device-del <device-id>"
For example, to hot unplug the vfio_ap mediated device identified on the
qemu command line with 'id=hostdev0' from the guest named 'my-guest':
virsh qemu-monitor-command my-guest --hmp "device_del hostdev0"
2. A vfio_ap mediated device can be hot unplugged by attaching the qemu monitor
to the guest and using the following qemu monitor command:
(QEMU) device-del id=<device-id>
For example, to hot unplug the vfio_ap mediated device that was specified
on the qemu command line with 'id=hostdev0' when the guest was started:
(QEMU) device-del id=hostdev0
After live migration of the KVM guest completes, an AP configuration can be
restored to the KVM guest by hot plugging a vfio_ap mediated device on the target
system into the guest in one of two ways:
1. If the KVM guest was started with libvirt, you can hot plug a matrix mediated
device into the guest via the following virsh commands:
virsh attach-device <guestname> <path-to-device-xml>
For example, to hot plug mdev 62177883-f1bb-47f0-914d-32a22e3a8804 into
the guest named 'my-guest':
virsh attach-device my-guest ~/config/my-guest-hostdev.xml
The contents of my-guest-hostdev.xml:
<hostdev mode='subsystem' type='mdev' managed='no' model='vfio-ap'>
<source>
<address uuid='62177883-f1bb-47f0-914d-32a22e3a8804'/>
</source>
</hostdev>
virsh qemu-monitor-command <guest-name> --hmp \
"device_add vfio-ap,sysfsdev=<path-to-mdev>,id=<device-id>"
For example, to hot plug the vfio_ap mediated device
62177883-f1bb-47f0-914d-32a22e3a8804 into the guest named 'my-guest' with
device-id hostdev0:
virsh qemu-monitor-command my-guest --hmp \
"device_add vfio-ap,\
sysfsdev=/sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804,\
id=hostdev0"
2. A vfio_ap mediated device can be hot plugged by attaching the qemu monitor
to the guest and using the following qemu monitor command:
(qemu) device_add "vfio-ap,sysfsdev=<path-to-mdev>,id=<device-id>"
For example, to plug the vfio_ap mediated device
62177883-f1bb-47f0-914d-32a22e3a8804 into the guest with the device-id
hostdev0:
(QEMU) device-add "vfio-ap,\
sysfsdev=/sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804,\
id=hostdev0"