On 05/05/2020 15.50, Cornelia Huck wrote:
> Add a basic example for passing a dasd via vfio-ccw.
>
> Signed-off-by: Cornelia Huck <coh...@redhat.com>
> ---
> docs/system/s390x/vfio-ccw.rst | 58 ++++++++++++++++++++++++++++++++++
> docs/system/target-s390x.rst | 1 +
> 2 files changed, 59 insertions(+)
> create mode 100644 docs/system/s390x/vfio-ccw.rst
>
> diff --git a/docs/system/s390x/vfio-ccw.rst b/docs/system/s390x/vfio-ccw.rst
> new file mode 100644
> index 000000000000..3b465578971f
> --- /dev/null
> +++ b/docs/system/s390x/vfio-ccw.rst
> @@ -0,0 +1,58 @@
> +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
> +DASD have really been tested.
s/DASD/DASDs/ ?
> +Example configuration
> +---------------------
> +
> +Step 1: configure the host device
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +Note: it is recommended to use the ``mdevctl`` tool for this step.
Can you also give an example on how to use it?
> If this
> +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
I'd remove the "[root@host ~]" part from all examples.
> +* 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 a uuid)::
> +
> + [root@host ~]# uuidgen
> + 7e270a25-e163-4922-af60-757fc8ed48c6
> + [root@host ~]# echo "7e270a25-e163-4922-af60-757fc8ed48c6" >
> /sys/bus/css/devices/0.0.0313/mdev_supported_types/vfio_ccw-io/create
Maybe break the long line with a backslash?
> +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 CHPIDs
> + ----------------------------------------------------------------------
> + 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
Here I'd add a sentence saying that you could run "dmesg -t" now to
check the kernel log. Then omit the timestamp in the example output
below, that will shorten the lines quite a bit.
> + [ 197.011652] dasd-eckd 0.0.1234: A channel path to the device has
> become operational
> + [ 197.014468] dasd-eckd 0.0.1234: New DASD 3390/0E (CU 3990/01) with
> 10017 cylinders, 15 heads, 224 sectors
> + [ 197.045606] dasd-eckd 0.0.1234: DASD with 4 KB/block, 7212240 KB
> total size, 48 KB/track, compatible disk layout
> + [ 197.049034] dasda:VOL1/ 0X2B09: dasda1
Thomas
