From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754483AbZGDJfn (ORCPT ); Sat, 4 Jul 2009 05:35:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751790AbZGDJfd (ORCPT ); Sat, 4 Jul 2009 05:35:33 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:57665 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751534AbZGDJfc (ORCPT ); Sat, 4 Jul 2009 05:35:32 -0400 To: Ingo Molnar Cc: Suresh Siddha , Gleb Natapov , "linux-kernel\@vger.kernel.org" , Sheng Yang , "kvm\@vger.kernel.org" , "avi\@redhat.com" References: <20090701133007.GC27539@redhat.com> <1246482017.27006.10670.camel@localhost.localdomain> <20090703082905.GF21833@elte.hu> From: ebiederm@xmission.com (Eric W. Biederman) Date: Sat, 04 Jul 2009 02:35:30 -0700 In-Reply-To: <20090703082905.GF21833@elte.hu> (Ingo Molnar's message of "Fri\, 3 Jul 2009 10\:29\:05 +0200") Message-ID: User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-XM-SPF: eid=;;;mid=;;;hst=in01.mta.xmission.com;;;ip=76.21.114.89;;;frm=ebiederm@xmission.com;;;spf=neutral X-SA-Exim-Connect-IP: 76.21.114.89 X-SA-Exim-Rcpt-To: mingo@elte.hu, avi@redhat.com, kvm@vger.kernel.org, sheng@linux.intel.com, linux-kernel@vger.kernel.org, gleb@redhat.com, suresh.b.siddha@intel.com X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-DCC: XMission; sa01 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Ingo Molnar X-Spam-Relay-Country: X-Spam-Report: * -1.8 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa01 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 XM_SPF_Neutral SPF-Neutral * 0.4 UNTRUSTED_Relay Comes from a non-trusted relay Subject: Re: [PATCH v5] enable x2APIC without interrupt remapping under KVM X-SA-Exim-Version: 4.2.1 (built Thu, 25 Oct 2007 00:26:12 +0000) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ingo Molnar writes: > * Suresh Siddha wrote: > >> On Wed, 2009-07-01 at 06:30 -0700, Gleb Natapov wrote: >> > KVM would like to provide x2APIC interface to a guest without emulating >> > interrupt remapping device. The reason KVM prefers guest to use x2APIC >> > is that x2APIC interface is better virtualizable and provides better >> > performance than mmio xAPIC interface: >> > >> > - msr exits are faster than mmio (no page table walk, emulation) >> > - no need to read back ICR to look at the busy bit >> > - one 64 bit ICR write instead of two 32 bit writes >> > - shared code with the Hyper-V paravirt interface >> > >> > Included patch changes x2APIC enabling logic to enable it even if IR >> > initialization failed, but kernel runs under KVM and no apic id is >> > greater than 255 (if there is one spec requires BIOS to move to x2apic >> > mode before starting an OS). >> > >> > Signed-off-by: Gleb Natapov >> >> Acked-by: Suresh Siddha > > Now, since this affects core x86 APIC code non-trivially so should > submitted to and go via the x86 tree. (Can prepare a special branch > with just this change if KVM tree wants/needs to pull it before > v2.6.32.) Please don't separate the x2apic code from the dmar code for this reason. Supporting hotplug cpus with ioapics is torture. Eric