From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: Re: [PATCH v5] enable x2APIC without interrupt remapping under KVM Date: Sat, 04 Jul 2009 17:22:01 -0700 Message-ID: References: <20090701133007.GC27539@redhat.com> <1246482017.27006.10670.camel@localhost.localdomain> <20090703082905.GF21833@elte.hu> <20090704095556.GB24641@redhat.com> <20090704155002.GC24641@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ingo Molnar , Suresh Siddha , "linux-kernel\@vger.kernel.org" , Sheng Yang , "kvm\@vger.kernel.org" , "avi\@redhat.com" To: Gleb Natapov Return-path: Received: from out01.mta.xmission.com ([166.70.13.231]:35452 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752690AbZGEAWD (ORCPT ); Sat, 4 Jul 2009 20:22:03 -0400 In-Reply-To: <20090704155002.GC24641@redhat.com> (Gleb Natapov's message of "Sat\, 4 Jul 2009 18\:50\:02 +0300") Sender: kvm-owner@vger.kernel.org List-ID: Gleb Natapov writes: >> Therefore I don't see the point of supporting one without the other. > x2apic provide us with other benefits as commit message explains, and > doesn't add any problems that we don't have now already. If this code has a legitimate place on real hardware I am all for it. If this is just a hack to make virtualization faster I don't like the extra code paths in the middle core architecture code. That will be a support burden for the foreseeable future. More code to test etc. Quickly skimming the patch it just appears to stir a mess. Plus it adds weird paravirtualization checks, ??? If we are going to have a special code path for virtual hardware can we do it right and have something nice to use that makes life simpler? For what we want to do with ioapics they suck and are really not suitable. The only thing that recommends them is that they are standard. But you are deviating from the standard so what is the point. Eric