From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36745) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bFdAC-0003lG-Q0 for qemu-devel@nongnu.org; Wed, 22 Jun 2016 04:05:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bFdA6-0007vH-I9 for qemu-devel@nongnu.org; Wed, 22 Jun 2016 04:05:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33890) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bFdA6-0007vB-Ch for qemu-devel@nongnu.org; Wed, 22 Jun 2016 04:05:26 -0400 Date: Wed, 22 Jun 2016 10:05:52 +0200 From: Jiri Denemark Message-ID: <20160622080552.GJ2450045@orkuz.home> References: <1466514153-85777-1-git-send-email-dahi@linux.vnet.ibm.com> <20160621164431.GI2048@thinpad.lan.raisama.net> <20160621190144.174c93cd@thinkpad-w530> <20160621203309.GK2048@thinpad.lan.raisama.net> <20160621210949.GH4783@orkuz.home> <20160622085140.06984206@thinkpad-w530> <20160622072621.GH2450045@orkuz.home> <20160622093449.6084d7d8@thinkpad-w530> <20160622075327.GI2450045@orkuz.home> <20160622095451.11a00cac@thinkpad-w530> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160622095451.11a00cac@thinkpad-w530> Subject: Re: [Qemu-devel] [RFC 00/28] s390x CPU models: exposing features List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Hildenbrand Cc: Eduardo Habkost , qemu-devel@nongnu.org, imammedo@redhat.com, cornelia.huck@de.ibm.com, borntraeger@de.ibm.com, fiuczy@linux.vnet.ibm.com, mimu@linux.vnet.ibm.com, libvir-list@redhat.com On Wed, Jun 22, 2016 at 09:54:51 +0200, David Hildenbrand wrote: > > On Wed, Jun 22, 2016 at 09:34:49 +0200, David Hildenbrand wrote: > > > I think the coffee didn't do its work already :) . I wanted to write that we can > > > _with_ this additional query. Meaning the involved overhead would be ok - in my > > > opinion for s390x. > > > > > > What we could do to avoid one compare operation would be: > > > > > > a) Expand the host model > > > b) Expand the target model (because on s390x we could have migration unsafe > > > model) > > > c) Work with the runnability information returned via query-cpu-definitions > > > > > > But as we have to do b) either way on s390x, we can directly do a compare > > > operation. (which makes implementation a lot simpler, because libvirt then > > > doesn't have to deal with any feature/model names). > > > > But why do you even need to do any comparison? Isn't it possible to let > > QEMU do it when a domain starts? The thing is we should avoid doing > > completely different things on each architecture. > > > > Sure, QEMU will of course double check when starting the guest! So trying to > start and failing is of course an option! So no check is needed if that is > acceptable. Yeah, I think it's the safest and easiest option now. Jirka