Re: [PATCH] qemu: fix command line building for iommu devices

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On Mon, Oct 03, 2016 at 02:32:01PM +0100, Daniel P. Berrange wrote:
On Mon, Oct 03, 2016 at 02:23:38PM +0100, Daniel P. Berrange wrote:
On Mon, Oct 03, 2016 at 03:11:37PM +0200, Martin Kletzander wrote:
> On Mon, Oct 03, 2016 at 03:02:38PM +0200, Peter Krempa wrote:
> > On Mon, Oct 03, 2016 at 13:41:13 +0100, Daniel Berrange wrote:
> > > The intel-iommu device has existed since QEMU 2.2.0, but
> > > it was only possible to create it with -device since
> > > QEMU 2.7.0, thanks to:
> > >
> > >   commit 621d983a1f9051f4cfc3f402569b46b77d8449fc
> > >   Author: Marcel Apfelbaum <marcel@xxxxxxxxxx>
> > >   Date:   Mon Jun 27 18:38:34 2016 +0300
> > >
> > >     hw/iommu: enable iommu with -device
> > >
> > >     Use the standard '-device intel-iommu' to create the IOMMU device.
> > >     The legacy '-machine,iommu=on' can still be used.
> > >
> > > The libvirt capability check & command line formatting code
> > > is thus broken for all QEMU versions 2.2.0 -> 2.6.0 inclusive.
> > >
> > > This fixes it to use iommu=on instead.
> > >
> > > Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>
> > > ---
> >
> > Is there any value to make it work with older versions rather than just
> > clearing it completely on the versions that don't support it with
> > -device?
> >
>
> I had one question as well.  Are those invocations migration-compatible?
> I can't try it right now, so I figured asking would be faster than
> preparing two machines with different QEMU versions =)  If they are not,
> then I would just say clear it.

Not sure, I'll investigate that.

The device is non-migratable

$ qemu-system-x86_64 -machine q35 -device intel-iommu -nodefaults -nodefconfig -S -monitor stdio
QEMU 2.7.50 monitor - type 'help' for more information
(qemu) migrate "exec:dd of=machine.img"
State blocked by non-migratable device 'iommu-intel'


OK, then it's just a matter of deciding whether we allow the old
-machine iommu=on for older QEMU.  Also we should disable the migration
of course, but that's not what you were trying to do in this patch, I know.

Regards,
Daniel
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