From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41941) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c72OS-0000MK-NM for qemu-devel@nongnu.org; Wed, 16 Nov 2016 10:45:04 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1c72OM-0003ab-SU for qemu-devel@nongnu.org; Wed, 16 Nov 2016 10:45:00 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:47853) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1c72OM-0003YG-Km for qemu-devel@nongnu.org; Wed, 16 Nov 2016 10:44:54 -0500 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uAGFiNnt065424 for ; Wed, 16 Nov 2016 10:44:52 -0500 Received: from e18.ny.us.ibm.com (e18.ny.us.ibm.com [129.33.205.208]) by mx0a-001b2d01.pphosted.com with ESMTP id 26rgyggtgu-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 16 Nov 2016 10:44:52 -0500 Received: from localhost by e18.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 16 Nov 2016 10:44:51 -0500 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> <20161116140537.GO5057@thinpad.lan.raisama.net> From: "Collin L. Walling" Date: Wed, 16 Nov 2016 10:44:47 -0500 MIME-Version: 1.0 In-Reply-To: <20161116140537.GO5057@thinpad.lan.raisama.net> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Message-Id: 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: Eduardo Habkost , jjherne@linux.vnet.ibm.com, borntraeger@de.ibm.com, libvir-list@redhat.com, Markus Armbruster , qemu-devel@nongnu.org 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 >>>>> 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. :)