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List: linux-s390
Subject: Re: [PATCH v8 00/13] basic channel IO passthrough infrastructure based on vfio
From: Cornelia Huck <cornelia.huck () de ! ibm ! com>
Date: 2017-05-18 13:13:56
Message-ID: 20170518151356.3dfc4207.cornelia.huck () de ! ibm ! com
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On Wed, 17 May 2017 02:48:00 +0200
Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:
> The patch series introduce a basic channel I/O passthrough
> infrastructure based on vfio.
> - Focus on supporting dasd-eckd(cu_type/dev_type = 0x3990/0x3390) as
> the target device.
> - Support new qemu parameters in the style of:
> -machine s390-ccw-virtio(,s390-squash-mcss=on|off) \
> -device vfio-ccw,sysfsdev=$MDEV_PATH
> We want to support real (i.e. not virtual) channel devices even for
> guests that do not support MCSS-E (where guests may see devices from
> any channel subsystem image at once). As all virtio-ccw devices are in
> css 0xfe (and show up in the default css 0 for guests not activating
> MCSS-E), we need an option to squash e.g. passed-through channel devices
> from their real css (0-3, or 0 for hosts not activating MCSS-E) into
> the default css, that is what the new machine option s390-squash-css is
> added.
Patches queued, with minor changes (see my comments).
I'll push out to s390-next once this passes some of my tests.
>
> Build and install:
> 1. kernel configuration
> CONFIG_S390_CCW_IOMMU=m
> CONFIG_VFIO=m
> CONFIG_VFIO_MDEV=m
> CONFIG_VFIO_MDEV_DEVICE=m
> CONFIG_VFIO_CCW=m
> 2. modules required
> modprobe vfio.ko
> modprobe mdev.ko
> modprobe vfio_mdev.ko
> modprobe vfio_iommu_type1.ko
> modprobe vfio_ccw.ko
> 3. find a subchannel(0.0."%schid") of a DASD-ECKD device and bind it to
> vfio_ccw driver
> #find the dasd you can use with lsdasd on your host. e.g.:
> devno="7e52"
> schid="16ca"
> #unbind the ccw device from the subchannel
> echo 0.0."$devno" > /sys/bus/ccw/devices/0.0."$devno"/driver/unbind
> #unbind the subchannel from io_subchannel driver
> echo 0.0."$schid" > /sys/bus/css/devices/0.0."$schid"/driver/unbind
> #bind the subchannel with vfio_ccw driver
> echo 0.0."$schid" > /sys/bus/css/drivers/vfio_ccw/bind
> 4. create a mediated device
> #generate a uuid with uuidgen. e.g.:
> uuid="6dfd3ec5-e8b3-4e18-a6fe-57bc9eceb920"
> echo "$uuid" > \
> /sys/bus/css/devices/0.0."$schid"/mdev_supported_types/vfio_ccw-io/create
> 5. pass-through this device to a vm
> -M s390-ccw-virtio,s390-squash-css=on \
> -device vfio-ccw,sysfsdev=/sys/bus/mdev/devices/$uuid \
> ... ...
These instructions would be helpful to preserve in the qemu wiki and
could even be expanded upon. Ping me if you need an account (hint,
hint ;)
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