Re: [Qemu-devel] [libvirt] [PATCH 3/5] qemu: add QEMU_CAPS_MACHINE_VMPORT_OPT

[Martin Kletzander]

On Tue, Apr 14, 2015 at 10:07:00AM -0600, Eric Blake wrote:
> [adding qemu]
>
> On 04/14/2015 09:58 AM, Marc-André Lureau wrote:
> > Hi
> >
> > On Tue, Apr 14, 2015 at 4:25 PM, Martin Kletzander <address@hidden>
> > wrote:
> >
> > > Is this not exposed in any way in QEMU?  Do we really need to use this
> > > (what we're trying to avoid)?
> >
> > That works with the following change:
> >
> > diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> > index 768cef1..1b20a7f 100644
> > --- a/src/qemu/qemu_capabilities.c
> > +++ b/src/qemu/qemu_capabilities.c
> > @@ -2510,6 +2510,7 @@ struct virQEMUCapsCommandLineProps {
> >
> >  static struct virQEMUCapsCommandLineProps virQEMUCapsCommandLine[] = {
> >      { "machine", "mem-merge", QEMU_CAPS_MEM_MERGE },
> > +    { "machine", "vmport", QEMU_CAPS_MACHINE_VMPORT_OPT },
>
> Ouch.  qemu commit 0a7cf21 fixes what would have been a regression in
> 2.3 at exposing "mem-merge" through query-command-line-options, but it
> does NOT expose "vmport", which is a per-architecture option rather than
> a generic -machine option.  Which means that even though qemu 2.2
> (perhaps wrongly) advertised "vmport" for all machines (even when it was
> not supported), 2.3 will not advertise it, and we are hoping for a
> better solution in 2.4 for properly advertising vmport on an
> as-appropriate basis.
>
> Yes, we WANT to use QMP probing,...
>
> >      { "drive", "discard", QEMU_CAPS_DRIVE_DISCARD },
> >      { "realtime", "mlock", QEMU_CAPS_MLOCK },
> >      { "boot-opts", "strict", QEMU_CAPS_BOOT_STRICT },
> > @@ -3243,10 +3244,6 @@ virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps,
> >      if (qemuCaps->version >= 1003000)
> >          virQEMUCapsSet(qemuCaps, QEMU_CAPS_MACHINE_USB_OPT);
> >
> > -    /* vmport option is supported v2.2.0 onwards */
> > -    if (qemuCaps->version >= 2002000)
> > -        virQEMUCapsSet(qemuCaps, QEMU_CAPS_MACHINE_VMPORT_OPT);
>
> ...and not version comparison, but we'll need something better in QMP
> for 2.3 (which is rather late, since we missed 2.3-rc3) if you can't
> come up with anything better for learning whether vmport is supported.

Ouch, I missed that.  But that's something we need for more than just
vmport attribute, but also all other machine-specific ones :(

I still think this might go in, though.

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