From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51774) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fqjDH-00060H-Oj for qemu-devel@nongnu.org; Fri, 17 Aug 2018 14:11:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fqjDD-0001P7-Nf for qemu-devel@nongnu.org; Fri, 17 Aug 2018 14:11:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59422) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fqjDD-0001Oq-IA for qemu-devel@nongnu.org; Fri, 17 Aug 2018 14:11:03 -0400 Date: Fri, 17 Aug 2018 15:10:57 -0300 From: Eduardo Habkost Message-ID: <20180817181057.GJ15372@localhost.localdomain> References: <1533909989-56115-1-git-send-email-robert.hu@linux.intel.com> <1533909989-56115-2-git-send-email-robert.hu@linux.intel.com> <20180817155524.GF15372@localhost.localdomain> <20180817174814.GI15372@localhost.localdomain> <1b71dd1c-59d2-324d-0284-0ea5869f4ec1@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1b71dd1c-59d2-324d-0284-0ea5869f4ec1@redhat.com> Subject: Re: [Qemu-devel] X86CPU "feature-words" property on QEMU (was Re: [PATCH v3 1/3] x86: Data structure changes to support MSR based) features List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Robert Hoo , rth@twiddle.net, thomas.lendacky@amd.com, qemu-devel@nongnu.org, robert.hu@intel.com, jingqi.liu@intel.com, Jiri Denemark , libvir-list@redhat.com On Fri, Aug 17, 2018 at 07:59:40PM +0200, Paolo Bonzini wrote: > On 17/08/2018 19:48, Eduardo Habkost wrote: > > So let's do what's necessary to remove it. But I don't think the > > removal of "feature-words" should block the inclusion of this > > series. > > > > Now, should QOM properties follow our feature deprecation policy, > > or they were never a supported external API and we can remove it > > immediately? > > > > CCing Jiri and libvir-list, because I just found that there's > > code on libvirt that uses it, but I don't know exactly it does > > with that info. > > It is used to check whether the host supports invtsc and pv-unhalt and > avoid changing the guest ABI when migrating: see > https://marc.info/?l=libvir-list&m=152445761414746&w=2 for a patch that > introduces one user. > > I think we should extend it to MSRs, not remove it. Well, I would prefer if libvirt simply did (e.g.) "qom-get property=invtsc" instead of fetching raw feature-words data. But if we do have an existing user, I now agree with you: let's keep it working and extend it to include MSR info too. BTW, libvirt must stop using this hardcoded QOM path: #define QOM_CPU_PATH "/machine/unattached/device[0]" It should use the "qom_path" field of "query-cpus" instead. -- Eduardo