> From: Zhenyu Wang
> Sent: Thursday, March 26, 2020 4:22 PM
>
> On 2020.03.26 08:17:20 +0000, Tian, Kevin wrote:
> > > From: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
> > > Sent: Thursday, March 26, 2020 1:42 PM
> > >
> > > Update doc for mdev aggregation support. Describe mdev generic
> > > parameter directory under mdev device directory.
> > >
> > > Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
> > > Cc: "Jiang, Dave" <dave.jiang@xxxxxxxxx>
> > > Signed-off-by: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
> > > ---
> > > .../driver-api/vfio-mediated-device.rst | 19 +++++++++++++++++++
> > > 1 file changed, 19 insertions(+)
> > >
> > > diff --git a/Documentation/driver-api/vfio-mediated-device.rst
> > > b/Documentation/driver-api/vfio-mediated-device.rst
> > > index 25eb7d5b834b..29c29432a847 100644
> > > --- a/Documentation/driver-api/vfio-mediated-device.rst
> > > +++ b/Documentation/driver-api/vfio-mediated-device.rst
> > > @@ -269,6 +269,9 @@ Directories and Files Under the sysfs for Each
> mdev
> > > Device
> > > |--- [$MDEV_UUID]
> > > |--- remove
> > > |--- mdev_type {link to its type}
> > > + |--- mdev [optional]
> > > + |--- aggregated_instances [optional]
> > > + |--- max_aggregation [optional]
> > > |--- vendor-specific-attributes [optional]
> > >
> > > * remove (write only)
> > > @@ -281,6 +284,22 @@ Example::
> > >
> > > # echo 1 > /sys/bus/mdev/devices/$mdev_UUID/remove
> > >
> > > +* mdev directory (optional)
> >
> > It sounds confusing to me when seeing a 'mdev' directory under a
> > mdev instance. How could one tell which attribute should put inside
> > or outside of 'mdev'?
> >
>
> After mdev create you get uuid directory under normal device path, so
> from that point a 'mdev' directory can just tell this is a mdev
> device. And it's proposed by Alex before.
I didn't quite get. Isn't $MDEV_UUID plus mdev_type already tell this is
a mdev device? If it is insufficient, then we're broken already since there
is no such 'mdev' sub-directory before.
Alex?
>
> Currently only mdev core could create attribute e.g 'remove' under
> device dir, vendor specific attrs need to be in attrs group. So 'mdev'
> directory here tries to be optional generic interface.
I'm a bit confused. Then why cannot the new nodes exposed through
vendor specific attributes? I may overlook previous discussion why using
attrs group doesn't work here. 😊
>
> > > +
> > > +Vendor driver could create mdev directory to specify extra generic
> > > parameters
> > > +on mdev device by its type. Currently aggregation parameters are
> defined.
> > > +Vendor driver should provide both items to support.
> > > +
> > > +1) aggregated_instances (read/write)
> > > +
> > > +Set target aggregated instances for device. Reading will show current
> > > +count of aggregated instances. Writing value larger than
> max_aggregation
> > > +would fail and return error.
> >
> > Can one write a value multiple-times and at any time?
> >
>
> yeah, of coz multiple times, but normally won't succeed after open.
>
> > > +
> > > +2) max_aggregation (read only)
> > > +
> > > +Show maxium instances for aggregation.
> > > +
> >
> > "show maximum-allowed instances which can be aggregated for this
> device". is
> > this value static or dynamic? if dynamic then the user is expected to read
> this
> > field before every write. worthy of some clarification here.
>
> yeah, user needs to read this before setting actual number, either static or
> dynamic
> depends on vendor resource type.
Then adding above information might make the description clearer.
Thanks
Kevin
>
> Thanks
>
> >
> > > Mediated device Hot plug
> > > ------------------------
> > >
> > > --
> > > 2.25.1
> >
>
> --
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>
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