From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752221Ab3HQIY0 (ORCPT ); Sat, 17 Aug 2013 04:24:26 -0400 Received: from mail.skyhub.de ([78.46.96.112]:56325 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751942Ab3HQIYX (ORCPT ); Sat, 17 Aug 2013 04:24:23 -0400 Date: Sat, 17 Aug 2013 10:24:19 +0200 From: Borislav Petkov To: Ingo Molnar , Joe Perches Cc: Youquan Song , Yinghai Lu , Gleb Natapov , Youquan Song , Sheng Yang , Konrad Rzeszutek Wilk , Linux Kernel Mailing List , "H. Peter Anvin" , Thomas Gleixner Subject: Re: [PATCH] x86, apic: Enable x2APIC physical when cpu < 256 native Message-ID: <20130817082419.GA10005@pd.tnic> References: <1373592159-459-1-git-send-email-youquan.song@intel.com> <20130724062254.GA16400@redhat.com> <20130729170514.GB30371@linux-youquan.bj.intel.com> <20130814184040.GA6726@linux-youquan.bj.intel.com> <20130814111105.GA13772@gmail.com> <20130817134454.GA16835@linux-youquan.bj.intel.com> <20130817074256.GA18772@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20130817074256.GA18772@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 17, 2013 at 09:42:56AM +0200, Ingo Molnar wrote: > > * Youquan Song wrote: > > > > No problem - you might want to send another patch adding some comments to > > > the code, explaining why we don't switch to physical mode, quoting from > > > the SDM and so. > > > > Here is the revert patch. > > > > Subject: [PATCH] Revert "x86/apic: Enable x2APIC physical mode on native hardware too, when there are fewer than 256 CPUs" > > > > x2APIC without interrupt remapping is not architecture and no guarantee it > > will work in future. > > There are some words in SDM3, 10.12.7 Initialization by System > > Software Routing of device interrupts to local APIC units operating in > > x2APIC mode requires use of the interrupt-remapping architecture > > specified in the Intel Virtualization Technology for Directed I/O, > > Revision 1.3. Because of this, BIOS must enumerate support for and > > software must enable this interrupt remapping with Extended Interrupt > > Mode Enabled before it enabling x2APIC mode in the local APIC units. > > > > This reverts commit 3d1acb49d22fbbae96524040e9e2d4cbbb3adbef, do not use > > x2apic_pysical mode if interrupt remapping is not enabled even at CPU > > number fewer than 256. > > > > Signed-off-by: Youquan Song > > --- > > arch/x86/kernel/apic/apic.c | 7 +++++-- > > 1 files changed, 5 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c > > index d9dd5a6..eca89c5 100644 > > --- a/arch/x86/kernel/apic/apic.c > > +++ b/arch/x86/kernel/apic/apic.c > > @@ -1622,8 +1622,11 @@ void __init enable_IR_x2apic(void) > > goto skip_x2apic; > > > > if (ret < 0) { > > - /* IR is required if there is APIC ID > 255 */ > > - if (max_physical_apicid > 255) { > > + /* IR is required if there is APIC ID > 255 even when running > > + * under KVM > > + */ > > + if (max_physical_apicid > 255 || > > + !hypervisor_x2apic_available()) { > > Firstly, please use the customary (multi-line) comment > style: > > /* > * Comment ..... > * ...... goes here. > */ > > specified in Documentation/CodingStyle. This keeps popping up. Maybe it should be in checkpatch, Joe? With the special handling of net/ and drivers/net/ of course. -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. --