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Re: [Qemu-devel] [PATCH] migration: Don't activate block devices if usin

From: Kevin Wolf
Subject: Re: [Qemu-devel] [PATCH] migration: Don't activate block devices if using -S
Date: Tue, 10 Apr 2018 16:47:56 +0200
User-agent: Mutt/1.9.1 (2017-09-22)

Am 10.04.2018 um 16:22 hat Dr. David Alan Gilbert geschrieben:
> * Kevin Wolf (address@hidden) wrote:
> > Am 10.04.2018 um 12:40 hat Dr. David Alan Gilbert geschrieben:
> > > Hmm; having chatted to Jiri I'm OK with reverting it, on the condition
> > > that I actually understand how this alternative would work first.
> > > 
> > > I can't currently see how a block-inactivate would be used.
> > > I also can't see how a block-activate unless it's also with the
> > > change that you're asking to revert.
> > > 
> > > Can you explain the way you see it working?
> > 
> > The key is making the delayed activation of block devices (and probably
> > delayed announcement of NICs? - you didn't answer that part) optional
> > instead of making it the default.
> NIC announcments are broken in similar but slightly different ways;  we
> did have a series on list to help a while ago but it never got merged;
> I'd like to keep that mess separate.

Okay. I just thought that it would make sense to have clear migration
phases that are the same for all external resources that the QEMU
processes use.

> > We can use Jirka's suggestion of adding a migration capability that
> > enables it, or I suppose a new option to -incoming could work, too. It
> > doesn't really matter what the syntax is, but the management tool must
> > request it explicitly.
> A new capability is easy to gate the change in behaviour that this patch
> added; I'll do that first thing for 2.13 (given today is rc3 tag it's
> too late).
> However, once we turn this on, to cope with the situation of a block user
> that must start prior to the 'cont' when this behaviour is active, we'd
> also need the 'block-activate' command.

Yes, that's right.


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