On Thu, 27 Jun 2019 19:57:04 -0600
Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:
> On Thu, 27 Jun 2019 15:15:02 -0600
> Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:
>
> > On Thu, 27 Jun 2019 09:38:32 -0600
> > Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:
> > > > On 6/27/19 8:26 AM, Cornelia Huck wrote:
> > > > >
> > > > > {
> > > > > "foo": "1",
> > > > > "bar": "42",
> > > > > "baz": {
> > > > > "depends": ["foo", "bar"],
> > > > > "value": "plahh"
> > > > > }
> > > > > }
> > > > >
> > > > > Something like that?
> > >
> > > I'm not sure yet. I think we need to look at what's feasible (and
> > > easy) with jq. Thanks,
> >
> > I think it's not too much trouble to remove and insert into arrays, so
> > what if we were to define the config as:
> >
> > {
> > "mdev_type":"vendor-type",
> > "start":"auto",
> > "attrs": [
> > {"attrX":["Xvalue1","Xvalue2"]},
> > {"dir/attrY": "Yvalue1"},
> > {"attrX": "Xvalue3"}
> > ]
> > }
> >
> > "attr" here would define sysfs attributes under the device. The array
> > would be processed in order, so in the above example we'd do the
> > following:
> >
> > 1. echo Xvalue1 > attrX
> > 2. echo Xvalue2 > attrX
> > 3. echo Yvalue1 > dir/attrY
> > 4. echo Xvalue3 > attrX
> >
> > When starting the device mdevctl would simply walk the array, if the
> > attribute key exists write the value(s). If a write fails or the
> > attribute doesn't exist, remove the device and report error.
Yes, I think it makes sense to fail the startup of a device where we
cannot set all attributes to the requested values.
> >
> > I think it's easiest with jq to manipulate arrays by removing and
> > inserting by index. Also if we end up with something like above, it's
> > ambiguous if we reference the "attrX" key. So perhaps we add the
> > following options to the modify command:
> >
> > --addattr=ATTRIBUTE --delattr --index=INDEX --value=VALUE1[,VALUE2]
> >
> > We could handle it like a stack, so if --index is not supplied, add to
> > the end or remove from the end. If --index is provided, delete that
> > index or add the attribute at that index. So if you had the above and
> > wanted to remove Xvalue1 but keep the ordering, you'd do:
> >
> > --delattr --index=0
> > --addattr --index=0 --value=Xvalue2
> >
> > Which should results in:
> >
> > "attrs": [
> > {"attrX": "Xvalue2"},
> > {"dir/attrY": "Yvalue1"},
> > {"attrX": "Xvalue3"}
> > ]
Modifying by index looks reasonable; I just sent a pull request to
print the index of an attribute out as well, so it is easier to specify
the right attribute to modify.
> >
> > If we want to modify a running device, I'm thinking we probably want a
> > new command and options --attr=ATTRIBUTE --value=VALUE might suffice.
> >
> > Do we need to support something like this for the 'start' command or
> > should we leave that for simple devices and require a sequence of:
> >
> > # mdevctl define ...
> > # mdevctl modify --addattr...
> > ...
> > # mdevctl start
> > # mdevctl undefine
> >
> > This is effectively the long way to get a transient device. Otherwise
> > we'd need to figure out how to have --attr --value appear multiple
> > times on the start command line. Thanks,
What do you think of a way to specify JSON for the attributes directly
on the command line? Or would it be better to just edit the config
files directly?
>
> This is now implemented, and yes you can specify '--addattr remove
> --value 1' and mdevctl will immediately remove the device after it's
> created (more power to the admin). Listing defined devices also lists
Fun ;)
> any attributes defined for easy inspection. It is also possible to
> override the conversion of comma separated values into an array by
> encoding and escaping the comma. It's a little cumbersome, but
> possible in case a driver isn't fully on board with the one attribute,
> one value rule of sysfs. Does this work for vfio-ap? I also still
I do not have ap devices to actually test this with; but defining a
device and adding attributes seems to work.
> need to check if this allows an NVIDIA vGPU mdev to be configured such
> that the framerate limiter can be automatically controlled. Thanks,
>
> Alex
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