From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: KVM Processor cache size Date: Tue, 03 Aug 2010 08:33:56 +0300 Message-ID: <4C57AA44.5010307@redhat.com> References: <4C56BF6F.9040402@amd.com> <4C56C353.7020607@redhat.com> <4C574512.6030903@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Andre Przywara , Ricardo Martins , "kvm@vger.kernel.org" To: Anthony Liguori Return-path: Received: from mx1.redhat.com ([209.132.183.28]:45433 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754773Ab0HCFeI (ORCPT ); Tue, 3 Aug 2010 01:34:08 -0400 In-Reply-To: <4C574512.6030903@codemonkey.ws> Sender: kvm-owner@vger.kernel.org List-ID: On 08/03/2010 01:22 AM, Anthony Liguori wrote: > On 08/02/2010 08:08 AM, Avi Kivity wrote: >>> I sent a patch to include the cache size when using -cpu host, but >>> this has been n'acked because the benefit is not clear. >> >> >> Anthony, why was this NACKed? > > I didn't NACK it. > > My concern is that we're still not handling live migration with -cpu > host in any meaningful way. Exposing more details without addressing > live migration is going to increase the likelihood of major failure. -cpu host is never going to be live migratable unless your hosts are exactly equal. Its goal is to get the best performance, not best compatibility, similar to device assignment. > > We need to add cpuid information to live migration such that we can > generate a graceful failure during migration. Agreed, esp. as it contains state. > Really, we shouldn't have taken -cpu host in the first place without > this. Disagreed. For live migration the user needs to specify cpuid precisely. We do need to be able to specify the cache size parameters from the -cpu description, but that shouldn't stop -cpu host. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.