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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable 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 8D614C4360F for ; Thu, 21 Feb 2019 17:00:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5609E2077B for ; Thu, 21 Feb 2019 17:00:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726400AbfBURAp (ORCPT ); Thu, 21 Feb 2019 12:00:45 -0500 Received: from imap1.codethink.co.uk ([176.9.8.82]:43221 "EHLO imap1.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725823AbfBURAp (ORCPT ); Thu, 21 Feb 2019 12:00:45 -0500 Received: from [167.98.27.226] (helo=xylophone) by imap1.codethink.co.uk with esmtpsa (Exim 4.84_2 #1 (Debian)) id 1gwriD-00075H-7D; Thu, 21 Feb 2019 17:00:41 +0000 Message-ID: <1550768440.2925.259.camel@codethink.co.uk> Subject: Re: [PATCH stable-4.4.y] KVM: VMX: Fix x2apic check in vmx_msr_bitmap_mode() From: Ben Hutchings To: Greg Kroah-Hartman , Joerg Roedel Cc: Joerg Roedel , stable@vger.kernel.org, David Woodhouse , Paolo Bonzini , Jim Mattson , linux-kernel@vger.kernel.org Date: Thu, 21 Feb 2019 17:00:40 +0000 In-Reply-To: <20190221162032.GF25800@kroah.com> References: <20190221135213.23926-1-joro@8bytes.org> <20190221141530.GA18436@kroah.com> <20190221144701.GB8380@suse.de> <20190221162032.GF25800@kroah.com> Organization: Codethink Ltd. Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1+deb9u1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2019-02-21 at 17:20 +0100, Greg Kroah-Hartman wrote: > On Thu, Feb 21, 2019 at 03:47:01PM +0100, Joerg Roedel wrote: > > On Thu, Feb 21, 2019 at 03:15:30PM +0100, Greg Kroah-Hartman wrote: > > > Ugh, good catch! > > > > > > Any hint as to what type of testing that you did that caught this?  I > > > keep asking people to run some kvm tests, but so far no one is :( > > > > We caught this at SUSE while testing candidate kernel updates for one of > > our service packs using a 4.4-based kernel and debugging turned > > out that this is issue came in via stable-updates. We also build a > > vanilla-flavour of the kernel which is nearly identical to the upstream > > stable tree, but what usually ends up in testing is the full tree with > > other backports. > > > > This particular issue was found by updating some openstack machines with > > the candidate kernel, which then triggered the problem in some guests. > > It is also a very special one, since I was only able to trigger the > > problem on Westmere-based machines with a specific guest-config. > > Nice work.  Any chance that "test" could be added to the kvm testing > scripts that I think are being worked on somewhere?  Ideally we would > have caught this before it ever hit the stable tree. If I understood correctly, the bug is specific to my backport. > Due to the lack of > good KVM testing, that's one of the areas I am always most worried about > :( Since the behaviour in this area depends on the host CPU model this might not help much. Ben. -- Ben Hutchings, Software Developer   Codethink Ltd https://www.codethink.co.uk/ Dale House, 35 Dale Street Manchester, M1 2HF, United Kingdom