From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751186Ab0INFMs (ORCPT ); Tue, 14 Sep 2010 01:12:48 -0400 Received: from mga01.intel.com ([192.55.52.88]:8969 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750781Ab0INFMn (ORCPT ); Tue, 14 Sep 2010 01:12:43 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.56,362,1280732400"; d="scan'208";a="837398288" Subject: Re: [RFC 4/6] x86, NMI, Rewrite NMI handler From: Huang Ying To: Don Zickus Cc: Andi Kleen , Ingo Molnar , "H. Peter Anvin" , "linux-kernel@vger.kernel.org" In-Reply-To: <20100913140419.GA27371@redhat.com> References: <1284087065-32722-1-git-send-email-ying.huang@intel.com> <1284087065-32722-4-git-send-email-ying.huang@intel.com> <20100910155605.GG4879@redhat.com> <20100910180356.44ac7097@basil.nowhere.org> <20100910182952.GJ4879@redhat.com> <1284343770.3269.75.camel@yhuang-dev.sh.intel.com> <20100913140419.GA27371@redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 14 Sep 2010 13:12:41 +0800 Message-ID: <1284441161.2256.94.camel@yhuang-dev.sh.intel.com> Mime-Version: 1.0 X-Mailer: Evolution 2.30.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2010-09-13 at 22:04 +0800, Don Zickus wrote: > On Mon, Sep 13, 2010 at 10:09:30AM +0800, Huang Ying wrote: > > > The reason I asked was, I thought it would be easier to have a global > > > variable that tells the nmi handler which cpu has the NMI's routed to its > > > io port. This way if you want to swap out the bsp cpu, you could perhaps > > > just re-route the nmi to a new cpu and the global variable would be > > > updated accordingly? > > > > Then we need some kind of protection or race condition between > > re-routing NMI and updating the variable. Do you think so? > > Well, I thought the only reasonable place to update the variable is when > the cpu is being taken offline, during the MTRR update. Since no NMIs can > be processed when the cpu's are syncing their MTRR, there shouldn't be a > race condition, no? > > Then again I am probably missing something obvious. Like I don't know how > cpu's deal with interrupts/NMIs when they are going offline. > > It was just a thought to avoid the spinlock. Why do you hate spinlock inside NMI handler? I think it is safe and simple if only used in NMI handler. Best Regards, Huang Ying