From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51188) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bXVqF-0001LN-Oi for qemu-devel@nongnu.org; Wed, 10 Aug 2016 11:54:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bXVqB-0006yL-Ke for qemu-devel@nongnu.org; Wed, 10 Aug 2016 11:54:50 -0400 Message-ID: <1470844480.3959.14.camel@redhat.com> From: Andrea Bolognani Date: Wed, 10 Aug 2016 17:54:40 +0200 In-Reply-To: <20160810144116.GA4514@in.ibm.com> References: <20160810144116.GA4514@in.ibm.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] spapr: CPU compat option works only with -global for pseries-2.7 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: bharata@linux.vnet.ibm.com, qemu-devel@nongnu.org Cc: qemu-ppc@nongnu.org, david@gibson.dropbear.id.au, groug@kaod.org, thuth@redhat.com, imammedo@redhat.com, ehabkost@redhat.com, sbhat@linux.vnet.ibm.com On Wed, 2016-08-10 at 20:11 +0530, Bharata B Rao wrote: > Hi, >=C2=A0 > With CPU core hotplug support in pseries-2.7, we will have to specify > the compat type using -global only as we don't yet take care of parsing > -cpu cputype,compat=3D. >=C2=A0 > There have been patches to support that: >=C2=A0 > sPAPR specific one: https://lists.nongnu.org/archive/html/qemu-devel/20= 16-06/msg07564.html >=C2=A0 > PPC generic one: https://lists.gnu.org/archive/html/qemu-devel/2016-07/= msg02676.html >=C2=A0 > but the patch isn't upstream yet. >=C2=A0 > The result is that instead of specifying >=C2=A0 > -cpu host,compat=3Dpower7 for pseries-2.7, we will have to use >=C2=A0 > -cpu host -global driver=3Dhost-powerpc64-cpu,property=3Dcompat,value=3D= power7 >=C2=A0 > This behaviour is specific to pseries-2.7 and for earlier machine types > the original way of specifying compat with -cpu works. >=C2=A0 > Will this be a concern for libvirt ? Would it be difficult for libvirt = to > switch to -global when generating QEMU cmdline for compat mode for pser= ies-2.7 > machine. >=C2=A0 > Or, should we just include one of the above patches so that > -cpu cputype,compat=3D continues to work for peseries-2.7 ? I filed bugs for this yesterday: =C2=A0 https://bugzilla.redhat.com/1365643 (QEMU) =C2=A0 https://bugzilla.redhat.com/1365647 (libvirt) libvirt could certainly be adapted to use -global, but that would not benefit people running QEMU directly, or driving QEMU 2.7 with any existing libvirt version. Plus, it would not solve the issue with CPU models that include a dot in their names, as you already noted. I won't comment on the patches because I'm not qualified to :) But, assuming they both restore the previous behaviour, getting either one into 2.7 would definitely be great. --=C2=A0 Andrea Bolognani / Red Hat / Virtualization