From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37594) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1azr81-00065b-CJ for qemu-devel@nongnu.org; Mon, 09 May 2016 15:46:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1azr7w-0004K4-7g for qemu-devel@nongnu.org; Mon, 09 May 2016 15:46:04 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32840) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1azr7u-0004Ik-Ji for qemu-devel@nongnu.org; Mon, 09 May 2016 15:46:00 -0400 Date: Mon, 9 May 2016 16:45:33 -0300 From: Eduardo Habkost Message-ID: <20160509194533.GV4457@thinpad.lan.raisama.net> References: <1462558292-2126-1-git-send-email-ehabkost@redhat.com> <1462558292-2126-8-git-send-email-ehabkost@redhat.com> <20160509105453.57b54a89@thinkpad-w530> <20160509120041.GR4457@thinpad.lan.raisama.net> <20160509140505.701b9dd5@thinkpad-w530> <20160509123630.GS4457@thinpad.lan.raisama.net> <20160509150618.0a9fe227@thinkpad-w530> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160509150618.0a9fe227@thinkpad-w530> Subject: Re: [Qemu-devel] [PATCH 7/9] qmp: Add runnability information to query-cpu-definitions List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Hildenbrand Cc: qemu-devel@nongnu.org, Jiri Denemark , Andreas =?iso-8859-1?Q?F=E4rber?= , Igor Mammedov , libvir-list@redhat.com, Michael Mueller , Christian Borntraeger , Cornelia Huck , Markus Armbruster On Mon, May 09, 2016 at 03:06:18PM +0200, David Hildenbrand wrote: > > > > > > > > > > Just FYI, on other architectures (e.g. s390x), other conditions (e.g. cpu > > > > > generation) also define if a CPU model is runnable, so the pure availability of > > > > > features does not mean that a cpu model is runnable. > > > > > > > > > > We could have runnable=false and unavailable-features being an empty list. > > > > > > > > Even on those cases, can't the root cause be mapped to a QOM > > > > property name (e.g. "cpu-generation"), even if it's property that > > > > can't be changed by the user? > > > > > > In the current state, no. > > > > But it could be implemented by s390x in the future, if it's > > considered useful, right? > > Yes, we could fit that into read-only properties if we would ever need it > (like cpu-generation you mentioned and cpu-ga-level - both will always be > read-only). > > However we could come up with more optional fields for that in the future. > (like unsupported-values or sth. like that). I actually prefer > unavailable-features over runnability-blockers. > > > > > > > > > So I think for runnable=false: > > > a) unavailable-features set -> can be made runnable > > > b) unavailable-features not set -> cannot be made runnable > > > > > > would be enough. > > > > I understand it would be enough, but I would like to at least > > define semantics that would make sense for all architectures in > > case it gets implemented in the future. Would the proposal below > > make sense? > > > > Yes, I think so. However to really make good hints, upper layers would most > likely need more information about the exact problem with a property - > maybe something like an enum value per problematic property. > (UNAVAILABLE_FEATURE, VALUE_TOO_BIG, VALUE_TOO_SMALL, UNSUPPORTED_VALUE) ... If a more powerful interface is needed, we can add extra fields, yes. Although I'm not sure we really start providing that level of detail in a generic way (I guess it will depend on how much arch-independent code libvirt will use to handle runnability information). > > > > > > > > > We could replace this with something more generic, like: > > > > > > > > @runnability-blockers: List of attributes that prevent the CPU > > > > model from running in the current host. > > > > > > > > A list of QOM property names that represent CPU model > > > > attributes that prevent the CPU from running. If the QOM > > > > property is read-only, that means the CPU model can never run > > > > in the current host. If the property is read-write, it means > > > > that it MAY be possible to run the CPU model in the current > > > > host if that property is changed. > > > > > > > > Management software can use it as hints to suggest or choose an > > > > alternative for the user, or just to generate meaningful error > > > > messages explaining why the CPU model can't be used. > > > > > > > > (I am looking for a better name than "runnability-blockers"). > > > > > > Not sure which approach would be better. Note that this is only a change in documentation of the new field, to allow it to cover extra cases without any changes in the interface. I also don't like the "runnability-blockers" name, but I prefer the new documentation I wrote above because it is more explicit about what exactly the field means. I plan to keep the "unavailable-features" name but use the above documentation text in the next version. Does that sound OK? -- Eduardo