From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:47765) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h2EPF-00020u-Kk for qemu-devel@nongnu.org; Fri, 08 Mar 2019 07:15:19 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h2EPA-0001SD-Rp for qemu-devel@nongnu.org; Fri, 08 Mar 2019 07:15:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59116) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1h2EPA-0001F5-JI for qemu-devel@nongnu.org; Fri, 08 Mar 2019 07:15:12 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6AA8081E18 for ; Fri, 8 Mar 2019 12:15:10 +0000 (UTC) From: Markus Armbruster References: <20190222153254.22739-1-stefanha@redhat.com> <20190308103532.GF12318@stefanha-x1.localdomain> Date: Fri, 08 Mar 2019 13:15:01 +0100 In-Reply-To: <20190308103532.GF12318@stefanha-x1.localdomain> (Stefan Hajnoczi's message of "Fri, 8 Mar 2019 10:35:32 +0000") Message-ID: <87imwtef5m.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH] qmp: add query-qemu-capabilities List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, Peter Krempa Stefan Hajnoczi 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 >> Cc: Peter Krempa >> Signed-off-by: Stefan Hajnoczi >> --- >> 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.