Re: [PATCH RFC v2 07/12] vfio/ccw: vfio based subchannel passthrough driver

Dong Jia Shi
2017-01-18T03:22:23Z

* Alex Williamson <alex.williamson@redhat.com> [2017-01-17 15:49:28 -0700]:

> On Thu, 12 Jan 2017 08:25:08 +0100
> Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:
>
> > From: Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> >
> > We use the IOMMU_TYPE1 of VFIO to realize the subchannels
> > passthrough, implement a vfio based subchannels passthrough
> > driver called "vfio-ccw".
> >
> > Support qemu parameters in the style of:
> > "-device vfio-ccw,id=xx,hostid=xx(,guestid=xx),mdevid=xx"
>
> Why not adopt the same syntax as vfio-pci with mdev devices,
> sysfsdev=%s where %s is a path to the mdev device in sysfs, which can
> be /sys/bus/mdev/devices/$UUID or as you create from the hostid
> below /sys/bus/css/devices/%x.%x.%04x/$UUID.
Ok. This is a good point.

I will change the cmdline interface to:
-device vfio-ccw,id=xx,sysfsdev=xx(,devno=xx)

Since "hostid" is removed, I will also rename "guestid" to "devno" to
make it looking consistent with the virtio-ccw devices.

> It seems if we know where
> to find the mdev device then we can determine the parent information on
> our own through sysfs.
>
This is true.

> > Signed-off-by: Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
[...]

--
Dong Jia