linux-imx

s390: vfio-ap: sysfs interfaces to configure domains

Introduces two new sysfs attributes for the VFIO mediated
matrix device for assigning AP domains to and unassigning
AP domains from a mediated matrix device. The IDs of the
AP domains assigned to the mediated matrix device will be
stored in an AP queue mask (AQM).

The bits in the AQM, from most significant to least
significant bit, correspond to AP queue index (APQI) 0 to
255 (note that an APQI is synonymous with with a domain ID).
On some systems, the maximum allowable domain number may be
less than 255 - depending upon the host's AP configuration -
and assignment may be rejected if the input domain ID exceeds
the limit.

When a domain is assigned, the bit corresponding to the APQI
will be set in the AQM. Likewise, when a domain is unassigned,
the bit corresponding to the APQI will be cleared from the AQM.

In order to successfully assign a domain, the APQNs derived from
the domain ID being assigned and the adapter numbers of all
adapters previously assigned:

1. Must be bound to the vfio_ap device driver.

2. Must not be assigned to any other mediated matrix device.

If there are no adapters assigned to the mdev, then there must
be an AP queue bound to the vfio_ap device driver with an
APQN containing the domain ID (i.e., APQI), otherwise all
adapters subsequently assigned will fail because there will be no
AP queues bound with an APQN containing the APQI.

Assigning or un-assigning an AP domain will also be rejected if
a guest using the mediated matrix device is running.

The relevant sysfs structures are:

/sys/devices/vfio_ap/matrix/
...... [mdev_supported_types]
......... [vfio_ap-passthrough]
............ [devices]
...............[$uuid]
.................. assign_domain
.................. unassign_domain

To assign a domain to the $uuid mediated matrix device,
write the domain's ID to the assign_domain file. To
unassign a domain, write the domain's ID to the
unassign_domain file. The ID is specified using
conventional semantics: If it begins with 0x, the number
will be parsed as a hexadecimal (case insensitive) number;
if it begins with 0, it will be parsed as an octal number;
otherwise, it will be parsed as a decimal number.

For example, to assign domain 173 (0xad) to the mediated matrix
device $uuid:

	echo 173 > assign_domain

	or

	echo 0255 > assign_domain

	or

	echo 0xad > assign_domain

To unassign domain 173 (0xad):

	echo 173 > unassign_domain

	or

	echo 0255 > unassign_domain

	or

	echo 0xad > unassign_domain

Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Tested-by: Michael Mueller <mimu@linux.ibm.com>
Tested-by: Farhan Ali <alifm@linux.ibm.com>
Tested-by: Pierre Morel <pmorel@linux.ibm.com>
Message-Id: <20180925231641.4954-8-akrowiak@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>