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

[Eric Blake <eblake@redhat.com>]

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[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 <mkletzan@redhat.com>
> 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.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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