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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/system/s390x/vfio-ccw.rst | 77 | ||||
| -rw-r--r-- | docs/system/target-s390x.rst | 1 |
2 files changed, 78 insertions, 0 deletions
diff --git a/docs/system/s390x/vfio-ccw.rst b/docs/system/s390x/vfio-ccw.rst new file mode 100644 index 0000000000..8f65442c0f --- /dev/null +++ b/docs/system/s390x/vfio-ccw.rst @@ -0,0 +1,77 @@ +Subchannel passthrough via vfio-ccw +=================================== + +vfio-ccw (based upon the mediated vfio device infrastructure) allows to +make certain I/O subchannels and their devices available to a guest. The +host will not interact with those subchannels/devices any more. + +Note that while vfio-ccw should work with most non-QDIO devices, only ECKD +DASDs have really been tested. + +Example configuration +--------------------- + +Step 1: configure the host device +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +As every mdev is identified by a uuid, the first step is to obtain one:: + + [root@host ~]# uuidgen + 7e270a25-e163-4922-af60-757fc8ed48c6 + +Note: it is recommended to use the ``mdevctl`` tool for actually configuring +the host device. + +To define the same device as configured below to be started +automatically, use + +:: + + [root@host ~]# driverctl -b css set-override 0.0.0313 vfio_ccw + [root@host ~]# mdevctl define -u 7e270a25-e163-4922-af60-757fc8ed48c6 \ + -p 0.0.0313 -t vfio-ccw_io -a + +If using ``mdevctl`` is not possible or wanted, follow the manual procedure +below. + +* Locate the subchannel for the device (in this example, ``0.0.2b09``):: + + [root@host ~]# lscss | grep 0.0.2b09 | awk '{print $2}' + 0.0.0313 + +* Unbind the subchannel (in this example, ``0.0.0313``) from the standard + I/O subchannel driver and bind it to the vfio-ccw driver:: + + [root@host ~]# echo 0.0.0313 > /sys/bus/css/devices/0.0.0313/driver/unbind + [root@host ~]# echo 0.0.0313 > /sys/bus/css/drivers/vfio_ccw/bind + +* Create the mediated device (identified by the uuid):: + + [root@host ~]# echo "7e270a25-e163-4922-af60-757fc8ed48c6" > \ + /sys/bus/css/devices/0.0.0313/mdev_supported_types/vfio_ccw-io/create + +Step 2: configure QEMU +~~~~~~~~~~~~~~~~~~~~~~ + +* Reference the created mediated device and (optionally) pick a device id to + be presented in the guest (here, ``fe.0.1234``, which will end up visible + in the guest as ``0.0.1234``:: + + -device vfio-ccw,devno=fe.0.1234,sysfsdev=\ + /sys/bus/mdev/devices/7e270a25-e163-4922-af60-757fc8ed48c6 + +* Start the guest. The device (here, ``0.0.1234``) should now be usable:: + + [root@guest ~]# lscss -d 0.0.1234 + Device Subchan. DevType CU Type Use PIM PAM POM CHPID + ---------------------------------------------------------------------- + 0.0.1234 0.0.0007 3390/0e 3990/e9 f0 f0 ff 1a2a3a0a 00000000 + [root@guest ~]# chccwdev -e 0.0.1234 + Setting device 0.0.1234 online + Done + [root@guest ~]# dmesg -t + (...) + dasd-eckd 0.0.1234: A channel path to the device has become operational + dasd-eckd 0.0.1234: New DASD 3390/0E (CU 3990/01) with 10017 cylinders, 15 heads, 224 sectors + dasd-eckd 0.0.1234: DASD with 4 KB/block, 7212240 KB total size, 48 KB/track, compatible disk layout + dasda:VOL1/ 0X2B09: dasda1 diff --git a/docs/system/target-s390x.rst b/docs/system/target-s390x.rst index 2592a05303..644e404ef9 100644 --- a/docs/system/target-s390x.rst +++ b/docs/system/target-s390x.rst @@ -25,6 +25,7 @@ or vfio-ap is also available. s390x/vfio-ap s390x/css s390x/3270 + s390x/vfio-ccw Architectural features ====================== |