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

[Peter Krempa]

On Mon, Oct 03, 2016 at 14:04:02 +0100, Daniel Berrange 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 at redhat.com>
> > >   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 at redhat.com>
> > > ---
> > 
> > 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?
> 
> Err that's what this change does

I asked incorrectly. I see that this adds support to enabling the iommu
via -machine, but I want to know whether that is of any value.

I'd just drop the capability and allow it to work since 2.7.0 only as
it's a new feature anyways.