From: "Daniel P. Berrangé" <berrange@redhat.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Cornelia Huck <cohuck@redhat.com>,
Sylvain Bauza <sbauza@redhat.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>
Subject: Re: mdevctl: A shoestring mediated device management and persistence utility
Date: Thu, 20 Jun 2019 09:24:25 +0100 [thread overview]
Message-ID: <20190620082425.GB25448@redhat.com> (raw)
In-Reply-To: <20190619124633.1c573484@x1.home>
On Wed, Jun 19, 2019 at 12:46:33PM -0600, Alex Williamson wrote:
> On Wed, 19 Jun 2019 11:46:59 +0200
> Cornelia Huck <cohuck@redhat.com> wrote:
>
> > On Wed, 19 Jun 2019 08:28:02 +0100
> > Daniel P. Berrangé <berrange@redhat.com> wrote:
> >
> > > On Tue, Jun 18, 2019 at 04:12:10PM -0600, Alex Williamson wrote:
> > > > On Tue, 18 Jun 2019 14:48:11 +0200
> > > > Sylvain Bauza <sbauza@redhat.com> wrote:
> > > >
> > > > > On Tue, Jun 18, 2019 at 1:01 PM Cornelia Huck <cohuck@redhat.com> wrote:
> >
> > > > > > I think we need to reach consensus about the actual scope of the
> > > > > > mdevctl tool.
> > > > > >
> > > > > >
> > > > > Thanks Cornelia, my thoughts:
> > > > >
> > > > > - Is it supposed to be responsible for managing *all* mdev devices in
> > > > > > the system, or is it more supposed to be a convenience helper for
> > > > > > users/software wanting to manage mdevs?
> > > > > >
> > > > >
> > > > > The latter. If an operator (or some software) wants to create mdevs by not
> > > > > using mdevctl (and rather directly calling the sysfs), I think it's OK.
> > > > > That said, mdevs created by mdevctl would be supported by systemctl, while
> > > > > the others not but I think it's okay.
> > > >
> > > > I agree (sort of), and I'm hearing that we should drop any sort of
> > > > automatic persistence of mdevs created outside of mdevctl. The problem
> > > > comes when we try to draw the line between unmanaged and manged
> > > > devices. For instance, if we have a command to list mdevs it would
> > > > feel incomplete if it didn't list all mdevs both those managed by
> > > > mdevctl and those created elsewhere. For managed devices, I expect
> > > > we'll also have commands that allow the mode of the device to be
> > > > switched between transient, saved, and persistent. Should a user then
> >
> > Hm, what's the difference between 'saved' and 'persistent'? That
> > 'saved' devices are not necessarily present?
>
> It seems like we're coming up with the following classes:
>
> 1) transient
> a) mdevctl created
> b) foreign
> 2) defined
> a) automatic start-up
> b) manual start-up
>
> I was using persistent for 2b), but that's probably not a good name
> because devices can still be stopped, so they're not really
> persistently available even in this class.
NB, for terminology when libvirt calls something "persistent" it just
means that there's a configuration file recorded on disk, thus when you
stop the thing, you can still query its config & restart it from that
same config later.
The best solution for libvirt would be to cope with all 4 of those
classes. 1b is the least important for us, so not the end of the
world if it was missing.
> > > To my mind there shouldn't really need to be a difference between
> > > transient mdevs created by mdevctrl and mdevs created by an user
> > > directly using sysfs. Both are mdevs on the running system with
> > > no config file that you have to enumerate by looking at sysfs.
> > > This ties back to my belief that we shouldn't need to have any
> > > config on disk for a transient mdev, just discover them all
> > > dynamically when required.
> >
> > So mdevctl can potentially interact with any mdev device on the system,
> > it just has to be instructed by a user or software to do so? I think we
> > can work with that.
>
> Some TBDs around systemd/init support for transient devices and how
> transient devices can be promoted to defined. For instance if a
> vfio-ap device requires matrix programming after instantiation, can we
> glean that programming from sysfs or is there metadata irrecoverably
> lost if no config file is created for a transient device? This would
> also imply that a 1b) foreign device could not be promoted to 2x)
> defined device.
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
next prev parent reply other threads:[~2019-06-20 8:24 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-23 23:20 mdevctl: A shoestring mediated device management and persistence utility 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 [this message]
[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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190620082425.GB25448@redhat.com \
--to=berrange@redhat.com \
--cc=alex.williamson@redhat.com \
--cc=cohuck@redhat.com \
--cc=eskultet@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=kwankhede@nvidia.com \
--cc=libvir-list@redhat.com \
--cc=phrdina@redhat.com \
--cc=sbauza@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).