From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752164Ab1IUPeY (ORCPT ); Wed, 21 Sep 2011 11:34:24 -0400 Received: from merlin.infradead.org ([205.233.59.134]:33053 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751188Ab1IUPeX convert rfc822-to-8bit (ORCPT ); Wed, 21 Sep 2011 11:34:23 -0400 Subject: Re: [V5][PATCH 4/6] x86, nmi: add in logic to handle multiple events and unknown NMIs From: Peter Zijlstra To: Robert Richter Cc: Don Zickus , "x86@kernel.org" , Andi Kleen , "ying.huang@intel.com" , LKML , "paulmck@linux.vnet.ibm.com" , "avi@redhat.com" , "jeremy@goop.org" Date: Wed, 21 Sep 2011 17:33:52 +0200 In-Reply-To: <20110921151829.GC6063@erda.amd.com> References: <1316529792-6560-1-git-send-email-dzickus@redhat.com> <1316529792-6560-5-git-send-email-dzickus@redhat.com> <20110921100842.GA6063@erda.amd.com> <20110921140432.GP5795@redhat.com> <20110921151829.GC6063@erda.amd.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Mailer: Evolution 3.0.3- Message-ID: <1316619232.24750.2.camel@twins> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2011-09-21 at 17:18 +0200, Robert Richter wrote: > 1. The cpu executes some microcode or SMM code. > 2. HW triggers the first NMI, an NMI is pending. > 3. HW triggers a second NMI, the NMI is still pending. > 4. The cpu finished microcode or SMM code. > 5. NMI handler is called, no NMI pending anymore. > 6. Return from NMI handler. Even without SMM, all you need is two different NMI users to trigger while an NMI is in flight. Wouldn't be entirely impossible to trigger if you have non-fatal-MCE/hardware-NMI-switch/PMI all active.