From: Eduardo Habkost <ehabkost@redhat.com>
To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: "Daniel P. Berrangé" <berrange@redhat.com>,
"Juan Quintela" <quintela@redhat.com>,
qemu-devel@nongnu.org, "Markus Armbruster" <armbru@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Vitaly Kuznetsov" <vkuznets@redhat.com>
Subject: Re: [PATCH RFC] migration: warn about non-migratable configurations unless '--no-migration' was specified
Date: Mon, 19 Apr 2021 15:32:28 -0400 [thread overview]
Message-ID: <20210419193228.q5e6vdnqwygh22bq@habkost.net> (raw)
In-Reply-To: <YH3QRs7VUapXZaTj@work-vm>
On Mon, Apr 19, 2021 at 07:47:34PM +0100, Dr. David Alan Gilbert wrote:
> * Daniel P. Berrangé (berrange@redhat.com) wrote:
> > On Mon, Apr 19, 2021 at 06:15:56PM +0100, Daniel P. Berrangé wrote:
> > > On Mon, Apr 19, 2021 at 06:11:47PM +0100, Dr. David Alan Gilbert wrote:
> > > > * Eduardo Habkost (ehabkost@redhat.com) wrote:
> > > > > I would make live migration policy an enum, just to make sure
> > > > > we are explicit about the requirements:
> > > > >
> > > > > - UNKNOWN: this is the current state in QEMU 6.0, where we don't
> > > > > really know what the user expects.
> > > > > This can be the default on existing versioned machine types,
> > > > > just for compatibility.
> > > > > I suggest making this print warnings for every migration
> > > > > blocker (like this patch does).
> > > > > I suggest deprecating this behavior as soon as we can.
> > > > >
> > > > > - PREFERRED: try to make the VM migratable when possible, but
> > > > > don't print a warning or error out if migration is blocked.
> > > > > This seems to be the behavior expected by libvirt today.
> > > > >
> > > > > - NOT_NEEDED: live migration is not needed, and QEMU is free to
> > > > > enable features that block live migration or change guest ABI.
> > > > > We can probably make this the default on machine types that
> > > > > never supported live migration.
> > > >
> > > > I suggest you could do this by adding:
> > > > -warn-none-migratable
> > > > -no-warn-none-migratable
> > > >
> > > > and then argue about defaults another time.
> > >
> > > If we're going to add new args, lets at least future proof our
> > > approach with an extensible option that we can wire into QMP
> > > too later
> > >
> > > -migratable none|preferred|required
> > >
> > > and letting us add extra key/value pairs to tune it if desired.
> >
> > Having said that, we potentially don't need a dedicated arg if we
> > just make 'migratable=none|preferred|required' be a property of
> > the machine type and hook everything off that
>
> I think my only difficulty with that is that I don't find any of those
> 3 words 'obvious'.
Any suggestions of replacements for those 3 words?
Would the descriptions below be enough to clarify their meaning
in documentation?
- NONE: live migration is not needed, and device or machine code
is allowed to enable features that block live migration or
change guest ABI.
(Not implemented yet)
- PREFERRED: machine and device code should try to make the VM
migratable when possible, but won't emit a warning or error out
if migration is blocked.
(Current default behavior)
- REQUIRED: live migration support is required, and adding a
migration blocker will be an error.
(Implemented today by --only-migratable)
--
Eduardo
next prev parent reply other threads:[~2021-04-19 20:34 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-15 15:44 [PATCH RFC] migration: warn about non-migratable configurations unless '--no-migration' was specified Vitaly Kuznetsov
2021-04-15 16:04 ` Daniel P. Berrangé
2021-04-15 16:30 ` Eduardo Habkost
2021-04-15 16:40 ` Daniel P. Berrangé
2021-04-15 17:07 ` Daniel P. Berrangé
2021-04-15 17:28 ` Dr. David Alan Gilbert
2021-04-16 7:33 ` Vitaly Kuznetsov
2021-04-16 16:28 ` Eduardo Habkost
2021-04-17 9:33 ` Markus Armbruster
2021-04-19 16:42 ` Daniel P. Berrangé
2021-04-19 16:48 ` Eduardo Habkost
2021-04-19 17:11 ` Dr. David Alan Gilbert
2021-04-19 17:15 ` Daniel P. Berrangé
2021-04-19 17:17 ` Daniel P. Berrangé
2021-04-19 18:47 ` Dr. David Alan Gilbert
2021-04-19 19:32 ` Eduardo Habkost [this message]
2021-04-20 11:51 ` Dr. David Alan Gilbert
2021-04-20 13:48 ` Eduardo Habkost
2021-04-20 14:10 ` Dr. David Alan Gilbert
2021-04-20 14:15 ` Daniel P. Berrangé
2021-04-20 15:20 ` Eduardo Habkost
2021-04-17 9:35 ` Markus Armbruster
2021-04-19 7:26 ` Markus Armbruster
2021-04-19 15:46 ` Markus Armbruster
2021-04-18 15:53 ` Peter Maydell
2021-04-19 16:28 ` Eduardo Habkost
2021-04-19 16:37 ` Daniel P. Berrangé
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