On 11/16/2016 09:05 AM, Eduardo Habkost wrote:
On Wed, Nov 16, 2016 at 02:15:02PM +0100, Jiri Denemark wrote:
On Tue, Nov 15, 2016 at 11:44:00 -0200, Eduardo Habkost wrote:
CCing qemu-devel.
CCing Markus, in case he has any insights about the interface introspection.
On Tue, Nov 15, 2016 at 08:42:12AM +0100, Jiri Denemark wrote:
On Mon, Nov 14, 2016 at 18:02:29 -0200, Eduardo Habkost wrote:
On Mon, Nov 14, 2016 at 02:26:03PM -0500, Collin L. Walling wrote:
cpu features are passed to the qemu command with feature=on/off instead of +/-feature.
Signed-off-by: Collin L. Walling <walling@linux.vnet.ibm.com> If I'm not mistaken, the "feature=on|off" syntax was added on QEMU 2.0.0. Does current libvirt support older QEMU versions? Of course it does. I'd love to switch to feature=on|off, but how can we check if QEMU supports it? We can't really start using this syntax without it. Actually, I was wrong, this was added in v2.4.0. "feat=on|off" needs two things to work (in x86):
* Translation of all "foo=bar" options to QOM property setting. This was added in v2.0.0-rc0~162^2 * The actual QOM properties for feature names to be present. They were added in v2.4.0-rc0~101^2~1
So you can be sure "feat=on" is supported by checking if the feature flags are present in device-list-properties output for the CPU model. But device-list-properties is also messy[1].
Maybe we can use the availability of query-cpu-model-expansion to check if we can safely use the new "feat=on|off" system? It's easier than taking all the variables above into account. Yeah, this could work since s390 already supports query-cpu-model-expansion. It would cause feature=on|off not to be used on x86_64 with QEMU older than 2.9.0, but I guess that's not a big deal, is it? Not a problem, as we have no plans to remove +feat/-feat support in x86 anymore.
Beautiful. Thanks for your responses everyone. :)