On 03/20/2015 08:19 AM, Markus Armbruster wrote:
>> If (a working version of) this makes it in 2.3, libvirt WILL use it in
>> the next release. It will take me less than 5 minutes to write up the
>> libvirt patch, as long as the new option is advertised via
>> query-command-line-options (which means that QMP introspection of the
>> new option is a must for v2 :)
The real libvirt requirement is that the new option is accessible via
_some_ QMP command (doesn't have to be query-command-line-options, but
that is the most obvious).
>
> query-command-line-options covers only options using QemuOpts. Fixing
> that defect isn't in the cards for 2.3, which means I'll have to
> implement it with QemuOpts.
Makes sense, and is certainly easier than figuring out an alternative
QMP probing mechanism.
>
> Ways to do that:
>
> * Stick it into an existing QemuOpts option. Is there one that fits?
> --machine doesn't really fit.
Mostly agree; --machine is more for what the guest sees, while this has
no impact on the guest ABI. On the other hand, things like -machine
accel=[tcg|kvm] aren't necessarily guest visible either, so -machine has
tended to be a catch-all for other things. But that doesn't mean it
should continue to be one.
>
> * Create a new QemuOpts option for miscellaneous settings. Would --misc
> format-probing=off be too ugly? Got a better name than --misc?
The only clients using the new option will be machine generated, so I
don't think ugly appearance is a show-stopper. And -misc really does
sound like it is the most amenable to adding other random flags in the
future, so I can live with that name.
Unless anyone else has a better idea, '-misc format-probing=off' has my
vote and works for libvirt; it is only a two-line change to my libvirt
RFC patch:
diff --git i/src/qemu/qemu_capabilities.c w/src/qemu/qemu_capabilities.c
index b452a75..f7a46c1 100644
--- i/src/qemu/qemu_capabilities.c
+++ w/src/qemu/qemu_capabilities.c
@@ -2517,7 +2517,7 @@ static struct virQEMUCapsCommandLineProps
virQEMUCapsCommandLine[] = {
{ "msg", "timestamp", QEMU_CAPS_MSG_TIMESTAMP },
{ "numa", NULL, QEMU_CAPS_NUMA },
{ "drive", "throttling.bps-total-max", QEMU_CAPS_DRIVE_IOTUNE_MAX },
- { "no-format-probing", NULL, QEMU_CAPS_NO_FORMAT_PROBING },
+ { "misc", "format-probing", QEMU_CAPS_NO_FORMAT_PROBING },
};
static int
diff --git i/src/qemu/qemu_command.c w/src/qemu/qemu_command.c
index 1085639..08f6560 100644
--- i/src/qemu/qemu_command.c
+++ w/src/qemu/qemu_command.c
@@ -8674,7 +8674,7 @@ qemuBuildCommandLine(virConnectPtr conn,
}
if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_NO_FORMAT_PROBING) &&
!cfg->allowDiskFormatProbing)
- virCommandAddArg(cmd, "-no-format-probing");
+ virCommandAddArgList(cmd, "-misc", "format-probing=off", NULL);
/* Serial graphics adapter */
if (def->os.bios.useserial == VIR_TRISTATE_BOOL_YES) {
>
> Existing miscellaneous non-QemeOpts options could then (in 2.4!)
> become sugar for something in this option group, thus become available
> with -readconfig.
Nice way to plan for future cleanups. I also agree that while this one
option about format-probing is reasonable to get into 2.3, that any
other sugar cleanups are better deferred until after the freeze.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
Attachment:
signature.asc
Description: OpenPGP digital signature
-- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list