[PATCH v4 7/7] s390: vfio-ap: update documentation

Tony Krowiak
2019-06-13T19:40:26Z

This patch updates the vfio-ap documentation to include the information
below.

Changes made to the mdev matrix assignment interfaces:

* Allow assignment of APQNs that are not bound to the vfio-ap device
driver as long as they are not owned by a zcrypt driver as identified
in the AP bus sysfs apmask and aqmask interfaces.

* Allow assignment of an AP resource to a mediated device which is in use
by a guest to hot plug an adapter, domain and control domain into a
running guest.

* Allow unassignment of an AP resource from a mediated device which is in
use by a guest to hot unplug an adapter, domain and control domain from
a running guest.

This patch also:

* Clarifies the section on configuring the AP bus's apmask and aqmask.

* Adds sections on dynamic configuration using the SE or SCLP command.

Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
---
Documentation/s390/vfio-ap.txt | 292 ++++++++++++++++++++++++++++++-----------
1 file changed, 213 insertions(+), 79 deletions(-)

diff --git a/Documentation/s390/vfio-ap.txt b/Documentation/s390/vfio-ap.txt
index 65167cfe4485..9372a6570ce1 100644
--- a/Documentation/s390/vfio-ap.txt
+++ b/Documentation/s390/vfio-ap.txt
@@ -81,10 +81,19 @@ definitions:
which the AP command is to be sent for processing.

The AP bus will create a sysfs device for each APQN that can be derived from
- the cross product of the AP adapter and usage domain numbers detected when the
- AP bus module is loaded. For example, if adapters 4 and 10 (0x0a) and usage
- domains 6 and 71 (0x47) are assigned to the LPAR, the AP bus will create the
- following sysfs entries:
+ the Cartesian product of the AP adapter and usage domain numbers detected when
+ the AP bus module is loaded. For example, if adapters 4 and 10 (0x0a) and
+ usage domains 6 and 71 (0x47) are assigned to the LPAR, the Cartesian product
+ would be defined by the following table:
+
+ 06 71
+ +-----------+-----------+
+ 04 | (04,06) | (04,47) |
+ +-----------|-----------+
+ 10 | (0a,06) | (0a,47) |
+ +-----------|-----------+
+
+ The AP bus will create the following sysfs entries:

/sys/devices/ap/card04/04.0006
/sys/devices/ap/card04/04.0047
@@ -146,10 +155,20 @@ 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:
+
+
+ 05 06
+ +-----------+-----------+
+ 01 | (01,05) | (01,06) |
+ +-----------|-----------+
+ 02 | (02,05) | (02,06) |
+ +-----------|-----------+
+
+
+APQNs (01,05), (01,06), (02,05) and (02,06) 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
@@ -349,8 +368,9 @@ matrix device.
number of the the usage domain is echoed to 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 Caresian
+ product of the adapter and domain numbers assigned to the mediated matrix
+ device.
* assign_control_domain:
* unassign_control_domain:
Write-only attributes for assigning/unassigning an AP control domain
@@ -438,9 +458,10 @@ guest use.
Example:
=======
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:
+access to AP facilities. For this example, we will assume that adapters 4, 5
+and 6 and domains 4, 71 (0x47), 171 (0xab) and 255 (0xff) are assigned to the
+LPAR and are online. We will show how to configure three guests such that
+executing the lszcrypt command on the guests would look like this:

Guest1
------
@@ -466,7 +487,7 @@ Guest2
CARD.DOMAIN TYPE MODE
------------------------------
06 CEX5A Accelerator
-06.0047 CEX5A Accelerator
+06.0047 CEX5A AcceleratorNote that this directory may contain additional bindings depending upon what
06.00ff CEX5A Accelerator

These are the steps:
@@ -513,35 +534,44 @@ These are the steps:
/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.

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.
+
+ The Cartesian product of the APIDs set in the apmask and the APQIs set in
+ the aqmask identify the APQNs of AP queue devices owned by the zcrypt
+ device drivers.
+
+ Take, for example, the following masks:

- Take, for example, the following mask:
+ apmask: 0x7000000000000000000000000000000000000000000000000000000000000000

- 0x7dffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+ aqmask: 0x0180000000000000000000000000000000000000000000000000000000000000

- It indicates:
+ The bits set in apmask are bits 1, 2 and 3. The bits set in aqmask are bits
+ 7 and 8. The Cartesian product of the bits set in the two masks is:

- 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.
+ 07 08
+ +-----------+-----------+
+ 01 | (01,07) | (01,08) |
+ +-----------|-----------+
+ 02 | (02,07) | (02,08) |
+ +-----------|-----------+
+ 03 | (03,07) | (03,08) |
+ +-----------|-----------+

- 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.
+ The masks indicate that the queues with APQNs (01,07), (01,08), (02,07),
+ (02,08), (03,07) and (03,08) are owned by the zcrypt drivers. When the AP bus
+ detects an AP queue device, its APQN is checked against the set of APQNs
+ derived from the apmask and aqmask. If a match is detected, the zcrypt
+ device driver registered for the device type of the queue will be probed. If
+ a match is not detected and the device type of the queue is CEX4 or newer,
+ the vfio_ap device driver will be probed.

- By default, the two masks are set to reserve all APQNs for use by the default
+ By default, the two masks are set to reserve all APQNs for use by the zcrypt
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
@@ -554,8 +584,7 @@ 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
@@ -563,7 +592,7 @@ These are the steps:

* 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
+ number string must be prefixed with a ('+') or minus ('-') to indicate
the corresponding bit is to be switched on ('+') or off ('-'). Some
valid values are:

@@ -594,19 +623,26 @@ These are the steps:
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
+Recall that the Cartesian product of the APIDs set in the apmask and the APQIs
+set in the aqmask identify the APQNs of AP queue devices owned by the zcrypt
+device drivers. If an attempt is made to modify the apmask or aqmask such that
+one or more APQNs changes ownership from a the vfio_ap device driver to a zcrypt
+device driver and the APQN is assigned to a mediated device (see step 3 below),
+the operation will fail with an error ('Address already in use').

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:
+ There is no way to secure the specific 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, so we are left with either securing all queues on adapters 05 and
+ 06, or queues 0004, 0047, 00ab and 00ff can be secured on all adapters.
+
+ To secure all queues on adapters 05 and 05:

echo -5,-6 > /sys/bus/ap/apmask

+ To secure queues 0004, 0047, 00ab, and 00ff on all adapters:
+
echo -4,-0x47,-0xab,-0xff > /sys/bus/ap/aqmask

Or the masks can be set as follows:
@@ -617,14 +653,20 @@ These are the steps:
echo 0xf7fffffffffffffffeffffffffffffffffffffffffeffffffffffffffffffffe \
> 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:
+ For this example, we will choose to secure queues 0004, 0047, 00ab, and 00ff
+ on all adapters. This will result in AP queues 04.0004, 04.0047, 04.00ab,
+ 04.00ff, 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]
+ ......... [04.0004]
+ ......... [04.0047]
+ ......... [04.00ab]
+ ......... [04.00ff]
......... [05.0004]
......... [05.0047]
......... [05.00ab]
@@ -641,11 +683,12 @@ These are the steps:
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:
+ can be bound to the vfio_ap device driver, or those queues will not get bound
+ to any 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
+ 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.
@@ -747,37 +790,48 @@ These are the steps:
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).
+ * Each APQN that can be derived from the adapter ID and the IDs of
+ the previously assigned domains must not be reserved for use by the
+ zcrypt device drivers as specified by the /sys/bus/ap/apmask and
+ /sys/bus/ap/aqmask syfs interfaces. If any APQN is reserved, the operation
+ will terminate with an error (EADDRNOTAVAIL).

- No APQN that can be derived from the adapter ID and the IDs of the
+ * 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).

+ Note that adapters that are currently not available to the host may be
+ assigned to the mediated device. If the adapter subsequently becomes
+ available while a guest is using the mediated device, it will automatically
+ become available to the guest.
+
In order to successfully assign a domain:

* The domain number specified must represent a value from 0 up to the
maximum domain number configured for the system. If a domain number
higher than the maximum is specified, the operation will terminate with
- an error (ENODEV).
+ an error (ENODEV). The maximum domain number can be determined by
+ printing the sysfs /sys/bus/ap/ap_max_domain_id attribute:

- * 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).
+ cat /sys/bus/ap/ap_max_domain_id

- No APQN that can be derived from the domain ID and the IDs of the
+ * Each APQN that can be derived from the domain ID and the IDs of
+ the previously assigned adapters must not be reserved for use by the
+ zcrypt device drivers as specified by the /sys/bus/ap/apmask and
+ /sys/bus/ap/aqmask syfs interfaces. If any APQN is reserved, the operation
+ will terminate with an error (EADDRNOTAVAIL).
+
+ * 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).

+ Note that domains that are currently not available to the host may be
+ assigned to the mediated device. If the domain subsequently becomes
+ available while a guest is using the mediated device, it will automatically
+ become available to the guest.
+
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
@@ -822,16 +876,96 @@ Using our example again, to remove the mediated matrix device $uuid1:
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.
+Hot plug/unplug via mdev matrix device sysfs interfaces:
+=======================================================
+If an mdev matrix device is in use by a running guest, AP resources can be
+plugged into or unplugged from the guest via the mdev device's sysfs
+assignment interfaces. Below are some examples.
+
+ To plug adapter 10 into a running guest:
+
+ echo 0xa > assign_adapter
+
+ To unplug domain 5 from a running guest:
+
+ echo 5 > unassign_domain
+
+To display the matrix of a guest using the mdev matrix device:
+
+ cat guest_matrix
+
+If you attempt to display the guest matrix when a guest is not using the
+mdev matrix device, an error will be displayed (ENODEV). Note that adapters and
+domains that are not yet available or not yet assigned to the LPAR can be
+assigned and will become available to the guest as soon as they become available
+to the host.
+
+Dynamic Changes to AP Configuration using the Support Element (SE):
+==================================================================
+The SE can be used to dynamically make the following changes to the AP
+configuration for an LPAR in which a linux host is running:
+
+ * Configure one or more adapters on
+
+ Configuring an adapter on sets its state to online, thus making it
+ available to the LPAR to which it is assigned. When an adapter is
+ configured on, it immediately becomes available to the LPAR as well as to
+ any guests using a mediated device to which the adapter is assigned.
+
+ * Configure one or more adapters off
+
+ Configuring an adapter off sets its state to standby, thus making it
+ unavailable to the LPAR to which it is assigned. When an adapter is
+ configured off, it immediately becomes unavailable to the LPAR as well as
+ to any guests using a mediated device to which the adapter is assigned.
+
+ * Add adapters or domains to the LPAR configuration
+
+ Adapters and/or domains can be assigned to an LPAR using the Change LPAR
+ Cryptographic Controls task. To make dynamic changes to the AP
+ configuration for an LPAR Running a linux guest, the online adapters
+ assigned to the LPAR must first be configured off. After performing the
+ adapter and/or domain assignments, the AP resources will automatically
+ become available to the linux host running in the LPAR as well as any
+ guests using a mediated device to which the adpaters and/or domains are
+ assigned.
+
+ * Remove adapters or domains from the LPAR configuration
+
+ Adapters and/or domains can be unassigned from an LPAR using the Change
+ LPAR Cryptographic Controls task. To make dynamic changes to the AP
+ configuration for an LPAR Running a linux guest, the online adapters
+ assigned to the LPAR must first be configured off. After performing the
+ adapter and/or domain unassignments, the AP resources will automatically
+ become unavailable to the linux host running in the LPAR as well as any
+ guests using a mediated device to which the adpaters and/or domains are
+ assigned.
+
+Dynamic Changes to the AP Configuration using the SCLP command:
+==============================================================
+The following SCLP commands may be used to dynamically configure AP adapters on
+and off:
+
+* Configure Adjunct Processor
+
+ The 'Configure Adjunct Processor' command sets an AP adapter's state to
+ online, thus making it available to the LPARs to which it is assigned. It will
+ likewise become available to any linux guest using a mediated device to which
+ the adapter is assigned.
+
+* Deconfigure Adjunct Processor
+
+ The 'Deconfigure Adjunct Processor' command sets an AP adapter's state to
+ standby, thus making it unavailable to the LPARs to which it is assigned. It
+ will likewise become unavailable to any linux guest using a mediated device to
+ which the adapter is assigned.

-* 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 migration:
+==============
+Live guest migration is not supported for guests using AP devices. All AP
+devices in use by the guest must be unplugged prior to initiating live
+migration (see "Hot plug/unplug via mdev matrix device sysfs interfaces" section
+above). If you are using QEMU to run your guest and it supports hot plug/unplug
+of the vfio-ap device, this would be another option (consult the QEMU
+documentation for details).

-* Live guest migration is not supported for guests using AP devices.
--
2.7.4