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Date: Mon, 14 Jan 2019 12:52:05 +0100
From: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20190114115205.GD6837@linux.fritz.box>
References: <e5021228-184b-cc1b-7aba-3bba795127a6@msgid.tls.msk.ru>
	<20190114105132.GA2524@work-vm>
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Subject: Re: [Qemu-devel] 3.1: second invocation of migrate crashes qemu
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To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Michael Tokarev <mjt@tls.msk.ru>, quintela@redhat.com, qemu-devel <qemu-devel@nongnu.org>

Am 14.01.2019 um 11:51 hat Dr. David Alan Gilbert geschrieben:
> * Michael Tokarev (mjt@tls.msk.ru) wrote:
> > $ qemu-system-x86_64 -monitor stdio -hda foo.img
> > QEMU 3.1.0 monitor - type 'help' for more information
> > (qemu) stop
> > (qemu) migrate "exec:cat >/dev/null"
> > (qemu) migrate "exec:cat >/dev/null"
> > qemu-system-x86_64: /build/qemu/qemu-3.1/block.c:4647: bdrv_inactivate_recurse: Assertion `!(bs->open_flags & BDRV_O_INACTIVE)' failed.
> > Aborted
> 
> And on head as well;  it only happens if the 1st migrate is succesful;
> if it got cancelled the 2nd one works, so it's not too bad.
> 
> I suspect the problem here is all around locking/ownership - the block
> devices get shutdown at the end of migration since the assumption is
> that the other end has them open now and we had better release them.

Yes, only "cont" gets control back to the source VM.

I think we really should limit the possible monitor commands in the
postmigrate status, and possibly provide a way to get back to the
regular paused state (which means getting back control of the resources)
without resuming the VM first.

Kevin