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From: Cornelia Huck <cohuck@redhat.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: "Matthew Rosato" <mjrosato@linux.ibm.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"Libvirt Devel" <libvir-list@redhat.com>,
	"Kirti Wankhede" <kwankhede@nvidia.com>,
	"Erik Skultety" <eskultet@redhat.com>,
	"Pavel Hrdina" <phrdina@redhat.com>,
	"Daniel P. Berrangé" <berrange@redhat.com>,
	"Sylvain Bauza" <sbauza@redhat.com>,
	"Christophe de Dinechin" <dinechin@redhat.com>,
	"Tony Krowiak" <akrowiak@linux.ibm.com>
Subject: Re: mdevctl: A shoestring mediated device management and persistence utility
Date: Fri, 28 Jun 2019 11:06:48 +0200
Message-ID: <20190628110648.40e0607d.cohuck@redhat.com> (raw)
In-Reply-To: <20190627195704.66be88c8@x1.home>

On Thu, 27 Jun 2019 19:57:04 -0600
Alex Williamson <alex.williamson@redhat.com> wrote:

> On Thu, 27 Jun 2019 15:15:02 -0600
> Alex Williamson <alex.williamson@redhat.com> wrote:
> 
> > On Thu, 27 Jun 2019 09:38:32 -0600
> > Alex Williamson <alex.williamson@redhat.com> 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


  reply index

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-23 23:20 Alex Williamson
2019-05-24 10:11 ` Cornelia Huck
2019-05-24 14:43   ` Alex Williamson
2019-06-07 16:06   ` Halil Pasic
2019-06-11 19:45     ` Cornelia Huck
2019-06-11 20:28       ` Alex Williamson
2019-06-12  7:14         ` Cornelia Huck
2019-06-12 15:54           ` Halil Pasic
2019-06-13 10:02             ` Cornelia Huck
2019-06-12 15:07       ` Halil Pasic
2019-06-13 16:17 ` Christophe de Dinechin
2019-06-13 16:35   ` Alex Williamson
2019-06-14  9:54     ` [libvirt] " Christophe de Dinechin
2019-06-14 14:23       ` Alex Williamson
2019-06-14 15:06         ` Christophe de Dinechin
2019-06-14 16:04           ` Alex Williamson
2019-06-17 16:03             ` Cornelia Huck
2019-06-17 14:00 ` Daniel P. Berrangé
2019-06-17 14:54   ` Alex Williamson
2019-06-17 15:10     ` Daniel P. Berrangé
2019-06-17 17:05       ` Alex Williamson
2019-06-18  8:44         ` Daniel P. Berrangé
2019-06-18 11:01         ` Cornelia Huck
     [not found]           ` <CALOCmukPWiXiM+mN0hCTvSwfdHy5UdERU8WnvOXiBrMQ9tH3VA@mail.gmail.com>
2019-06-18 22:12             ` Alex Williamson
2019-06-19  7:28               ` Daniel P. Berrangé
2019-06-19  9:46                 ` Cornelia Huck
2019-06-19 18:46                   ` Alex Williamson
2019-06-20  8:24                     ` Daniel P. Berrangé
     [not found]               ` <CALOCmu=6Xmw-_-SVXujCEcgPY2CQiBQKgfUMJ45WnZ_9XORyUw@mail.gmail.com>
2019-06-19  9:57                 ` Cornelia Huck
2019-06-19 19:53                 ` Alex Williamson
2019-06-25 22:52 ` Alex Williamson
2019-06-26  9:58   ` Cornelia Huck
2019-06-26 14:37     ` Alex Williamson
2019-06-27  1:53       ` Alex Williamson
2019-06-27 12:26         ` Cornelia Huck
2019-06-27 15:00           ` Matthew Rosato
2019-06-27 15:38             ` Alex Williamson
2019-06-27 16:13               ` Matthew Rosato
2019-06-27 21:15               ` Alex Williamson
2019-06-28  1:57                 ` Alex Williamson
2019-06-28  9:06                   ` Cornelia Huck [this message]
2019-06-28 14:01                     ` Matthew Rosato
2019-06-28 17:05                     ` Alex Williamson
2019-07-01  8:20                       ` Cornelia Huck
2019-07-01 14:40                         ` Alex Williamson
2019-07-01 17:13                           ` Cornelia Huck

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