From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f198.google.com (mail-wr0-f198.google.com [209.85.128.198]) by kanga.kvack.org (Postfix) with ESMTP id 5863D6B0358 for ; Wed, 3 Jan 2018 10:48:38 -0500 (EST) Received: by mail-wr0-f198.google.com with SMTP id i6so1001465wre.6 for ; Wed, 03 Jan 2018 07:48:38 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id f8sor349023wmc.37.2018.01.03.07.48.36 for (Google Transport Security); Wed, 03 Jan 2018 07:48:36 -0800 (PST) Date: Wed, 3 Jan 2018 16:48:33 +0100 From: Ingo Molnar Subject: Re: "bad pmd" errors + oops with KPTI on 4.14.11 after loading X.509 certs Message-ID: <20180103154833.fhkbwonz6zhm26ax@gmail.com> References: <20180103084600.GA31648@trogon.sfo.coreos.systems> <20180103092016.GA23772@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180103092016.GA23772@kroah.com> Sender: owner-linux-mm@kvack.org List-ID: To: Greg Kroah-Hartman Cc: Benjamin Gilbert , x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org * Greg Kroah-Hartman wrote: > On Wed, Jan 03, 2018 at 12:46:00AM -0800, Benjamin Gilbert wrote: > > [resending with less web] > > (adding lkml and x86 developers) > > > Hi all, > > > > In our regression tests on kernel 4.14.11, we're occasionally seeing a run > > of "bad pmd" messages during boot, followed by a "BUG: unable to handle > > kernel paging request". This happens on no more than a couple percent of > > boots, but we've seen it on AWS HVM, GCE, Oracle Cloud VMs, and local QEMU > > instances. It always happens immediately after "Loading compiled-in X.509 > > certificates". I can't reproduce it on 4.14.10, nor, so far, on 4.14.11 > > with pti=off. Here's a sample backtrace: A few other things to check: first please test the latest WIP.x86/pti branch which has a couple of fixes. In a -stable kernel tree you should be able to do: git pull --no-tags git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git WIP.x86/pti in particular this recent fix from a couple of hours ago might make a difference: 52994c256df3: x86/pti: Make sure the user/kernel PTEs match Note that this commit: 694d99d40972: x86/cpu, x86/pti: Do not enable PTI on AMD processors disables PTI on AMD CPUs - so if you'd like to test it more broadly on all CPUs then you'll need to add "pti=on" to your boot commandline. Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org