From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40516) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ehd7n-0006OH-RE for qemu-devel@nongnu.org; Fri, 02 Feb 2018 10:19:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ehd7j-0004Y0-RN for qemu-devel@nongnu.org; Fri, 02 Feb 2018 10:19:35 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50996) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ehd7j-0004Xc-KT for qemu-devel@nongnu.org; Fri, 02 Feb 2018 10:19:31 -0500 Date: Fri, 2 Feb 2018 15:07:18 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20180202150718.GL15403@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20180201125441.2f5b4fdd@redhat.com> <20180201201514.GB660@flask> <20180201202649.GG26425@localhost.localdomain> <20180202141554.GH26425@localhost.localdomain> <20180202141938.GJ15403@redhat.com> <20180202092159.48d9bd4c@redhat.com> <20180202145014.GI26425@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180202145014.GI26425@localhost.localdomain> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [RFC] kvm: x86: export vCPU halted state to sysfs List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost Cc: Luiz Capitulino , Viktor Mihajlovski , Radim =?utf-8?B?S3LEjW3DocWZ?= , kvm@vger.kernel.org, pbonzini@redhat.com, Peter Krempa , John Ferlan , libvir-list@redhat.com, Christian Borntraeger , qemu-devel@nongnu.org, Markus Armbruster , Eric Blake On Fri, Feb 02, 2018 at 12:50:14PM -0200, Eduardo Habkost wrote: > (CCing qemu-devel) >=20 > On Fri, Feb 02, 2018 at 09:21:59AM -0500, Luiz Capitulino wrote: > > On Fri, 2 Feb 2018 14:19:38 +0000 > > Daniel P. Berrang=C3=A9 wrote: > > > On Fri, Feb 02, 2018 at 12:15:54PM -0200, Eduardo Habkost wrote: > [...] > > > > It would be also interesting to update QEMU QMP documentation to > > > > clarify the arch-specific semantics of "halted". =20 > > >=20 > > > Any also especially clarify the awful performance implications of r= unning > > > this particular query command. In general I would not expect query-= xxx > > > monitor commands to interrupt all vcpus, so we should clearly warn = about > > > this ! > >=20 > > Or deprecate it... >=20 > We could deprecate the expensive fields on query-cpus, and move > them to a more expensive query-cpu-state command. I believe most > users of query-cpus are only interested in qom_path, thread_id, > and topology info. >=20 > Markus, Eric: from the QAPI point of view, is it OK to remove > fields between QEMU versions, as long as we follow our > deprecation policy? I would expect that to not be OK. A fully backwards compatible way to deal with this would just be to add a flag to the query-cpus command eg something like query-cpus arch-specific=3Dfalse to turn off all this arch specific state, and just report the cheap generic info. If it defaults to arch-specific=3Dtrue when omitted, then there's no compat problems. Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberran= ge :| |: https://libvirt.org -o- https://fstop138.berrange.c= om :| |: https://entangle-photo.org -o- https://www.instagram.com/dberran= ge :|