From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34655) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bFcy9-000381-NZ for qemu-devel@nongnu.org; Wed, 22 Jun 2016 03:53:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bFcy6-0004wr-Ji for qemu-devel@nongnu.org; Wed, 22 Jun 2016 03:53:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36213) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bFcy6-0004wF-Dr for qemu-devel@nongnu.org; Wed, 22 Jun 2016 03:53:02 -0400 Date: Wed, 22 Jun 2016 09:53:27 +0200 From: Jiri Denemark Message-ID: <20160622075327.GI2450045@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160622093449.6084d7d8@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 09:34:49 +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. Jirka