From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 94D12C43387 for ; Wed, 19 Dec 2018 21:33:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 475BC2086C for ; Wed, 19 Dec 2018 21:33:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=explicate.org header.i=@explicate.org header.b="MbYXLfqU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730574AbeLSVdC (ORCPT ); Wed, 19 Dec 2018 16:33:02 -0500 Received: from www.explicate.org ([71.19.157.6]:34591 "EHLO smtp.svc.explicate.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728356AbeLSVdB (ORCPT ); Wed, 19 Dec 2018 16:33:01 -0500 X-Greylist: delayed 439 seconds by postgrey-1.27 at vger.kernel.org; Wed, 19 Dec 2018 16:33:01 EST Received: (qmail 455 invoked by uid 1000); 19 Dec 2018 21:25:37 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=explicate.org; i=@explicate.org; q=dns/txt; s=v01.y2019; t=1545254737; h=date : from : to : cc : subject : message-id : mime-version : content-type : date : from : subject; bh=+eubUdSQt4QBstvSvK+iLlr6a/+yAgIx/tB5PTy+mtw=; b=MbYXLfqUgBq6Q0PzELADeCC3SMpIAw/zBh8UqYP4oADudyfR0u+XJMY8 Xq0/4JMs6LhO5+8Jj3QZjCOGerSLHFhqnV6eEDRmirSAitWKj6BiPHUP+F z77CCuA9IPtsQMU+5mj8j1CJ1qRME/pQaTsbODUBOmzFTxNaVBxiDab+4= Date: Wed, 19 Dec 2018 13:25:37 -0800 From: Ken Pizzini To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Subject: PROBLEM: Xen paging-request boot failure since 4.19.5 Message-ID: <20181219212537.GA25174@144vak35.msa.explicate.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since 4.19.5 I have not been able to boot kernels on my Xen-hosted VM on a system with an Intel Xeon L5520 processor (microcode 0x1d). 4.19.4 worked fine; I've tried kernels 4.19.5, 4.19.6, 4.19.7 4.19.9, 4.19.10, 4.20-rc7, and they all throw: BUG: unable to handle kernel paging request at ffff88903fffc000 PGD 1c0c067 P4D 1c0c067 PUD 0 Oops: 0000 [#1] PREEMPT SMP NOPTI ... [register dump and call trace omitted, since I believe I located the offending source code] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 Kernel Offset: disabled early in the system boot (fine details might differ; I did not carefully record the result of each test). I finally had time to do some bisection, and the problem traces back to commit d52888aa2753e3063a9d3a0c9f72f94aa9809c15 in tree fbbb33771ac6c392caeb283163a594f1a7e6d04d (x86/mm: Move LDT remap out of KASLR region on 5-level paging). After backing-out this one commit, I have successfully built and booted 4.19.5, 4.19.10 and 4.20-rc7 (I haven't bothered trying other versions). (The VM is currently running my patched 4.19.10 without any apparent problem.) Notes: all 4.19.* builds are of Gentoo's "gentoo-sources" tree (which include standard Gentoo patches), plus wireguard; the 4.20-rc7 build was unpatched. I have been successfully running a different build of each 4.19.* version on my laptop (with many more device drivers enabled), so the problem is unlikely to be due to the build toolchain (which is common to both of my build trees). Let me know if there is more information that you would find helpful, or if you have patches that you'd like me to test. --Ken Pizzini