From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:43215) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T6QlJ-0007LL-E2 for qemu-devel@nongnu.org; Tue, 28 Aug 2012 14:43:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1T6QlH-0008Nm-U4 for qemu-devel@nongnu.org; Tue, 28 Aug 2012 14:43:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51679) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T6QlH-0008NW-M2 for qemu-devel@nongnu.org; Tue, 28 Aug 2012 14:43:39 -0400 Date: Tue, 28 Aug 2012 13:37:18 -0300 From: Marcelo Tosatti Message-ID: <20120828163718.GA460@amt.cnet> References: <20120828162317.GA30308@amt.cnet> <20120828163124.GB3245@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120828163124.GB3245@redhat.com> Subject: Re: [Qemu-devel] [PATCHv2 2/4] pc: refactor compat code List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: gleb@redhat.com, kvm@vger.kernel.org, qemu-devel@nongnu.org, Jan Kiszka , avi@redhat.com, Anthony Liguori On Tue, Aug 28, 2012 at 07:31:24PM +0300, Michael S. Tsirkin wrote: > On Tue, Aug 28, 2012 at 01:23:18PM -0300, Marcelo Tosatti wrote: > > On Mon, Aug 27, 2012 at 03:20:13PM +0300, Michael S. Tsirkin wrote: > > > In preparation to adding PV EOI migration for 1.2, > > > trivially refactor some some compat code > > > to make it easier to add version specific > > > cpuid tweaks. > > > > > > Signed-off-by: Michael S. Tsirkin > > > --- > > > hw/pc_piix.c | 44 ++++++++++++++++++++++++++++++++++++-------- > > > 1 file changed, 36 insertions(+), 8 deletions(-) > > > > Why can't you clear the cpuid bit in kvm paravirt leaf at hw/pc_piix.c, > > leaving compat code isolated there? > > This is not how we handle it for compat properties: > there we set flag in pc_piix and make devices look at > that flag. > And it makes sense because what you suggest does not scale: we can not > teach pc_piix about quirks of all hardware. What is there to scale? Old machines are static, they don't change. This way you are putting the burden of compat support in the generic driver code, which has better things to worry about than old machine types. IMO it is better to have all of the compat mess localized. > It will also scale better if we ever get interested about > compatibility and migration for non pc machines. > -- > MST Alright, will wait a couple of days before merging.