Stefan Hajnoczi <stefa...@redhat.com> writes: > On Fri, Feb 22, 2019 at 03:32:54PM +0000, Stefan Hajnoczi wrote: >> QMP clients can usually detect the presence of features via schema >> introspection. There are rare features that do not involve schema >> changes and are therefore impossible to detect with schema >> introspection. >> >> This patch adds the query-qemu-capabilities command. It returns a list >> of capabilities that this QEMU supports. >> >> The decision to make this a command rather than something statically >> defined in the schema is intentional. It allows QEMU to decide which >> capabilities are available at runtime, if necessary. >> >> This new interface is necessary so that QMP clients can discover that >> migrating disk image files is safe with cache.direct=off on Linux. >> There is no other way to detect whether or not QEMU supports this. >> >> Cc: Markus Armbruster <arm...@redhat.com> >> Cc: Peter Krempa <pkre...@redhat.com> >> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> >> --- >> qapi/misc.json | 42 ++++++++++++++++++++++++++++++++++++++++++ >> qmp.c | 18 ++++++++++++++++++ >> 2 files changed, 60 insertions(+) > > Markus: query-qemu-features is no longer needed by the page cache > invalidation feature since a related QMP schema change is being made now > and clients can detect the feature via that change. > > I'm inclined to leave this patch series for now. Later someone can pick > it up again if there is a feature that cannot be detected via a schema > change.
Mekse sense. I figure we'll likely want the command at some point. And that's when we should add it. Hold on to your git branch until then.