From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752624AbdKWGVX (ORCPT ); Thu, 23 Nov 2017 01:21:23 -0500 Received: from mail-wr0-f174.google.com ([209.85.128.174]:43813 "EHLO mail-wr0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752090AbdKWGVV (ORCPT ); Thu, 23 Nov 2017 01:21:21 -0500 X-Google-Smtp-Source: AGs4zMabsAWO/hmrFLN+iTDjU35eHe+CR6SWcg6ipxun24CuHZdj4ZkWsUw7lxXE92ffDy+XBYBClg== Date: Thu, 23 Nov 2017 07:21:17 +0100 From: Ingo Molnar To: Andy Lutomirski Cc: Thomas Gleixner , X86 ML , Borislav Petkov , "linux-kernel@vger.kernel.org" , Brian Gerst , Dave Hansen , Linus Torvalds , Josh Poimboeuf Subject: Re: [PATCH v2 00/18] Entry stack switching Message-ID: <20171123062117.bztoxdqd2iv7ipdn@gmail.com> References: <20171122062257.ivp5fbcy2k4mlfdm@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andy Lutomirski wrote: > On Tue, Nov 21, 2017 at 10:22 PM, Ingo Molnar wrote: > > > > * Andy Lutomirski wrote: > > > >> This sets up stack switching, including for SYSCALL. I think it's > >> in decent shape. > >> > >> Known issues: > >> - I think we're going to want a way to turn the stack switching on and > >> off either at boot time or at runtime. It should be fairly straightforward > >> to make it work. > >> > >> - I think the ORC unwinder isn't so good at dealing with stack overflows. > >> It bails too early (I think), resulting in lots of ? entries. This > >> isn't a regression with this series -- it's just something that could > >> be improved. > >> > >> Ingo, patch 1 may be tip/urgent material. It fixes what I think is > >> a bug in Xen. I'm having a hard time testing because it's being > >> masked by a bigger unrelated bug that's keeping Xen from booting > >> when configured to hit the bug I'm fixing. (The latter bug goes at > >> least back to v4.13, I think I know roughtly what's wrong, and I've > >> reported it to the maintainers.) > > > > Hm, with this series the previous IRQ vector bug appears again: > > > > [ 51.156370] do_IRQ: 16.34 No irq handler for vector > > [ 57.511030] do_IRQ: 16.34 No irq handler for vector > > [ 57.528335] do_IRQ: 16.34 No irq handler for vector > > [ 57.533256] do_IRQ: 16.34 No irq handler for vector > > [ 63.991913] do_IRQ: 16.34 No irq handler for vector > > [ 63.996810] do_IRQ: 16.34 No irq handler for vector > > > > I've attached the reproducer config. Note that the system appears to be working to > > a certain extent (I could ssh to it and extract its config), but produces these > > warnings sporadically. > > I'll try to reproduce this, but this is weird. This is vector 34, > which is, or could be, a genuine IRQ vector. The only way I can think > of that my series would have caused this is if I very severely broke > common_interrupt, but I don't see how that could have happened without > breaking everything. It's also weird that you're seeing this only on > CPU 16. Maybe it's worth adding a WARN_ON to that warning to get a > stack trace just in case. > > Thomas, any insight here? > > > but don't get the IRQ vector warnings. > > Ingo, are you saying that you only get the IRQ vector warnings with > the SYSCALL hwframe fix applied? That's bizarre. Correct. I assume it's because lockdep is working fine with that fix applied, but that also means that different irq-tracing code paths are taken. The lockdep error disables lockdep globally and immediately. > Anyway, I booted your config (more or less -- I munged it through > virtme-configkernel --update first) with 17 vCPUs and it seems fine. > Is the issue reliable enough to bisect? Ok, it should be bisectable, will try to bisect it. I think it's a key aspect that the CPU is AMD - a similar config on Intel seems to be working fine (modulo the unwinder warning). Thanks, Ingo