[libvirt] [PATCH 0/2] qemu: Enable -blockdev support (blockdev-add saga)

[Kevin Wolf]

Am 16.09.2019 um 11:32 hat Peter Krempa geschrieben:
> (ccing Kevin)
> 
> On Mon, Sep 16, 2019 at 10:14:44 +0100, Daniel Berrange wrote:
> > On Fri, Sep 13, 2019 at 02:43:53PM +0200, Peter Krempa wrote:
> > > To my knowledge, everything in libvirt is now prepared to fully use
> > > -blockdev way to configure disks in qemu.
> > > 
> > > There is one known qemu bug though: Internal snapshots don't work with
> > > -blockdev:
> > > 
> > > https://bugzilla.redhat.com/show_bug.cgi?id=1658981
> > 
> > What are the chances of that bug actually getting fixed any time in the
> > forseeable future ?
> > 
> > savevm has been a pain for a long time since it blocks QEMU and we've
> > been waiting for it to be fixedd by QEMU devs for at least 7-8 years
> > now, and I don't see anyone from QEMU block maintainers commenting on
> > this new BZ to indicate they're going to fix this latest problem.
> > 
> > > Since I can't in good faith ask for merging this patchset yet I'd like
> > > to give it some more testing I'm suggesting that we push it and revert
> > > it during freeze or add a capability check once qemu is fixed.
> > 
> > I'd only be in favour of enabling it if there is some clear time frame
> > on whicht hat bug above is likely to be fixed. I'm guesing it is pretty
> > unlikely to be fixed before our freeze, so I thinking speculatively
> > enabling it is premature.
> 
> I'm not sure. Kevin, any idea when we can expect the fix?
> 
> Otherwise the only option to enable blockdev would be to just enable it
> and blame qemu for internal snapshots not working.

The main problem with implementing a fix was that it's unclear what the
desired result even is. After some discussion with Max, I think we'll
try it with restricting snapshotting to everything that is directly
attached to a BlockBackend and monitor-owned nodes that don't have any
parents.

Kevin
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