From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752917AbZGBASS (ORCPT ); Wed, 1 Jul 2009 20:18:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752003AbZGBASE (ORCPT ); Wed, 1 Jul 2009 20:18:04 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:38912 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750969AbZGBASB (ORCPT ); Wed, 1 Jul 2009 20:18:01 -0400 To: suresh.b.siddha@intel.com Cc: Avi Kivity , Gleb Natapov , "linux-kernel\@vger.kernel.org" , Sheng Yang , "kvm\@vger.kernel.org" , garyhade@us.ibm.com References: <20090629132926.GB20289@redhat.com> <20090630092623.GI20289@redhat.com> <4A4A476C.2070305@redhat.com> <4A4A6499.9000406@redhat.com> <1246488808.27006.10691.camel@localhost.localdomain> From: ebiederm@xmission.com (Eric W. Biederman) Date: Wed, 01 Jul 2009 17:17:57 -0700 In-Reply-To: <1246488808.27006.10691.camel@localhost.localdomain> (Suresh Siddha's message of "Wed\, 01 Jul 2009 15\:53\:28 -0700") 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=in02.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: suresh.b.siddha@intel.com, garyhade@us.ibm.com, kvm@vger.kernel.org, sheng@linux.intel.com, linux-kernel@vger.kernel.org, gleb@redhat.com, avi@redhat.com X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-DCC: XMission; sa03 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;suresh.b.siddha@intel.com 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 * [sa03 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 v3] 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 in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Suresh Siddha writes: > On Tue, 2009-06-30 at 12:36 -0700, Eric W. Biederman wrote: >> Dropped irqs.. Driver hangs because it is waiting for an irq. Hardware >> hangs because it is waiting for the cpu to process the irq. >> >> Potentially we get a level triggered irq that is never acked by >> the cpu that won't arm until the cpu send an ack, and we can't >> send an ack from another cpu. > > Eric, > > Among number of experiments you have tried in the past to fix this, have > you tried the experiment of explicitly clearing the remoteIRR by > changing the trigger mode to edge and then back to level. > > Is there a problem with this? The problem I had wasn't remoteIRR getting stuck, but the symptoms were largely the same. I did try changing the trigger mode to edge and back and that did not unstick the ioapic in all cases. > We can send a spurious IPI (after the RTE migration) with the new vector > to another cpu and handler which services the level interrupt will check > if we saw the edge mode for a level interrupt and then the handler can > explicitly restore the level trigger and reset the remote IRR by mask > +edge and unmask+level. > > We might have to work with some rough edges but do you recollect any > major issue with this approach.. This is coming up enough recently I expect it is time to cook up a patch that does the ioapic migration in process context plus some user space code that stress tests things. Just so people can repeat my experiments and see what I am trying to avoid. Eric