From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:49807) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RmsWa-0007CJ-MO for qemu-devel@nongnu.org; Mon, 16 Jan 2012 14:47:28 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RmsWW-0000LR-Eo for qemu-devel@nongnu.org; Mon, 16 Jan 2012 14:47:24 -0500 Received: from e36.co.us.ibm.com ([32.97.110.154]:59830) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RmsWW-0000LE-8k for qemu-devel@nongnu.org; Mon, 16 Jan 2012 14:47:20 -0500 Received: from /spool/local by e36.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 16 Jan 2012 12:47:17 -0700 Received: from d03relay03.boulder.ibm.com (d03relay03.boulder.ibm.com [9.17.195.228]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 54FBF19D804A for ; Mon, 16 Jan 2012 12:47:02 -0700 (MST) Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay03.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q0GJl3Jt168258 for ; Mon, 16 Jan 2012 12:47:03 -0700 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q0GJl1SY032084 for ; Mon, 16 Jan 2012 12:47:01 -0700 Date: Mon, 16 Jan 2012 13:46:57 -0600 From: Ryan Harper Message-ID: <20120116194657.GD25198@us.ibm.com> References: <1326066759-8210-1-git-send-email-agraf@suse.de> <1326066759-8210-2-git-send-email-agraf@suse.de> <20120116193005.GC25198@us.ibm.com> <47E08DA5-61EF-4DF8-AB22-E1BF42807602@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <47E08DA5-61EF-4DF8-AB22-E1BF42807602@suse.de> Subject: Re: [Qemu-devel] [PATCH 2/2] KVM: Use -cpu best as default on x86 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: Ryan Harper , "qemu-devel@nongnu.org Developers" , kvm list , Avi Kivity * Alexander Graf [2012-01-16 13:37]: > > On 16.01.2012, at 20:30, Ryan Harper wrote: > > > * Alexander Graf [2012-01-08 17:53]: > >> When running QEMU without -cpu parameter, the user usually wants a sane > >> default. So far, we're using the qemu64/qemu32 CPU type, which basically > >> means "the maximum TCG can emulate". > > > > it also means we all maximum possible migration targets. Have you > > given any thought to migration with -cpu best? > > If you have the same boxes in your cluster, migration just works. If > you don't, you usually use a specific CPU model that is the least > dominator between your boxes either way. Sure, but the idea behind -cpu best is to not have to figure that out; you had suggested that the qemu64/qemu32 were just related to TCG, and what I'm suggesting is that it's also the most compatible w.r.t migration. it sounds like if migration is a requirement, then -cpu best probably isn't something that would be used. I suppose I'm OK with that, or at least I don't have a better suggestion on how to carefully push up the capabilities without at some point breaking migration. > > The current kvm64 type is broken. Libgmp just abort()s when we pass it > in. So anything is better than what we do today on AMD hosts :). I wonder if it breaks with Cyris cpus... other tools tend to do runtime detection (mplayer). > > > Alex -- Ryan Harper Software Engineer; Linux Technology Center IBM Corp., Austin, Tx ryanh@us.ibm.com