On Thu, 27 Jun 2019 11:00:31 -0400
Matthew Rosato <mjrosato@xxxxxxxxxxxxx> wrote:
> On 6/27/19 8:26 AM, Cornelia Huck wrote:
> > On Wed, 26 Jun 2019 19:53:50 -0600
> > Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:
> >
> >> On Wed, 26 Jun 2019 08:37:20 -0600
> >> Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:
> >>
> >>> On Wed, 26 Jun 2019 11:58:06 +0200
> >>> Cornelia Huck <cohuck@xxxxxxxxxx> wrote:
> >>>
> >>>> On Tue, 25 Jun 2019 16:52:51 -0600
> >>>> Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:
> >>>>
> >>>>> Hi,
> >>>>>
> >>>>> Based on the discussions we've had, I've rewritten the bulk of
> >>>>> mdevctl. I think it largely does everything we want now, modulo
> >>>>> devices that will need some sort of 1:N values per key for
> >>>>> configuration in the config file versus the 1:1 key:value setup we
> >>>>> currently have (so don't consider the format final just yet).
> >>>>
> >>>> We might want to factor out that config format handling while we're
> >>>> trying to finalize it.
> >>>>
> >>>> cc:ing Matt for his awareness. I'm currently not quite sure how to
> >>>> handle those vfio-ap "write several values to an attribute one at a
> >>>> time" requirements. Maybe 1:N key:value is the way to go; maybe we
> >>>> need/want JSON or something like that.
> >>>
> >>> Maybe we should just do JSON for future flexibility. I assume there
> >>> are lots of helpers that should make it easy even from a bash script.
> >>> I'll look at that next.
> >>
> >> Done. Throw away any old mdev config files, we use JSON now.
> >
> > The code changes look quite straightforward, thanks.
> >
> >> The per
> >> mdev config now looks like this:
> >>
> >> {
> >> "mdev_type": "i915-GVTg_V4_8",
> >> "start": "auto"
> >> }
> >>
> >> My expectation, and what I've already pre-enabled support in set_key
> >> and get_key functions, is that we'd use arrays for values, so we might
> >> have:
> >>
> >> "new_key": ["value1", "value2"]
> >>
> >> set_key will automatically convert a comma separated list of values
> >> into such an array, so I'm thinking this would be specified by the user
> >> as:
> >>
> >> # mdevctl modify -u UUID --key=new_key --value=value1,value2
> >
> > Looks sensible.
> >
> > For vfio-ap, we'd probably end up with something like the following:
> >
> > {
> > "mdev_type": "vfio_ap-passthrough",
> > "start": "auto",
> > "assign_adapter": ["5", "6"],
> > "assign_domain": ["4", "0xab"]
> > }
> >
> > (following the Guest1 example in the kernel documentation)
> >
> > <As an aside, what should happen if e.g "assign_adapter" is set to
> > ["6", "7"]? Remove 5, add 7? Remove all values, then set the new ones?
>
> IMO remove 5, add 7 would make the most sense. I'm not sure that doing
> an unassign of all adapters (effectively removing all APQNs) followed by
> an assign of the new ones would work nicely with Tony's vfio-ap dynamic
> configuration patches.
Are we conflating operating on the config file versus operating on the
device? I was thinking that setting a new key value replaces the
existing key, because anything else adds unnecessary complication to
the code and command line. So in the above example, if the user
specified:
mdevctl modify -u UUID --key=assign_adapter --value=6,7
The new value is simply ["6", "7"]. This would take effect the next
time the device is started. We haven't yet considered how to change
running devices, but I think the semantics we have since the respin of
mdevctl separate saved config vs running devices in order to generalize
the support of transient devices.
> > Similar for deleting the "assign_adapter" key. We have an
> > "unassign_adapter" attribute, but this is not something we can infer
> > automatically; we need to know that we're dealing with an vfio-ap
> > matrix device...>
> >
> >>
> >> We should think about whether ordering is important and maybe
> >> incorporate that into key naming conventions or come up with some
> >> syntax for specifying startup blocks. Thanks,
> >>
> >> Alex
> >
> > Hm...
> >
> > {
> > "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,
Alex
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