From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42521) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c70qO-0002IC-Ju for qemu-devel@nongnu.org; Wed, 16 Nov 2016 09:05:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1c70qL-0001fH-7R for qemu-devel@nongnu.org; Wed, 16 Nov 2016 09:05:44 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46042) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1c70qL-0001dj-0m for qemu-devel@nongnu.org; Wed, 16 Nov 2016 09:05:41 -0500 Date: Wed, 16 Nov 2016 12:05:37 -0200 From: Eduardo Habkost Message-ID: <20161116140537.GO5057@thinpad.lan.raisama.net> References: <1479151563-13473-1-git-send-email-walling@linux.vnet.ibm.com> <1479151563-13473-2-git-send-email-walling@linux.vnet.ibm.com> <20161114200229.GG5057@thinpad.lan.raisama.net> <20161115074212.GB4015667@orkuz.home> <20161115134400.GH5057@thinpad.lan.raisama.net> <20161116131502.GB2238061@orkuz.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161116131502.GB2238061@orkuz.home> Subject: Re: [Qemu-devel] [libvirt] [PATCH v1] qemu: command: rework cpu feature argument support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Collin L. Walling" , jjherne@linux.vnet.ibm.com, borntraeger@de.ibm.com, libvir-list@redhat.com, Markus Armbruster , qemu-devel@nongnu.org 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 > > > > > > > > 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. -- Eduardo