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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 A4C11CA9EA3 for ; Fri, 18 Oct 2019 09:02:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 87C1F2064B for ; Fri, 18 Oct 2019 09:02:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2633011AbfJRJCx (ORCPT ); Fri, 18 Oct 2019 05:02:53 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:56120 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2437687AbfJRJCx (ORCPT ); Fri, 18 Oct 2019 05:02:53 -0400 Received: from p5b06da22.dip0.t-ipconnect.de ([91.6.218.34] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1iLO9f-0002Y0-4q; Fri, 18 Oct 2019 11:02:39 +0200 Date: Fri, 18 Oct 2019 11:02:37 +0200 (CEST) From: Thomas Gleixner To: Xiaoyao Li cc: Paolo Bonzini , Sean Christopherson , Fenghua Yu , Ingo Molnar , Borislav Petkov , H Peter Anvin , Peter Zijlstra , Andrew Morton , Dave Hansen , Radim Krcmar , Ashok Raj , Tony Luck , Dan Williams , Sai Praneeth Prakhya , Ravi V Shankar , linux-kernel , x86 , kvm@vger.kernel.org Subject: Re: [RFD] x86/split_lock: Request to Intel In-Reply-To: <5da90713-9a0d-6466-64f7-db435ba07dbe@intel.com> Message-ID: References: <1560897679-228028-1-git-send-email-fenghua.yu@intel.com> <1560897679-228028-10-git-send-email-fenghua.yu@intel.com> <20190626203637.GC245468@romley-ivt3.sc.intel.com> <20190925180931.GG31852@linux.intel.com> <3ec328dc-2763-9da5-28d6-e28970262c58@redhat.com> <57f40083-9063-5d41-f06d-fa1ae4c78ec6@redhat.com> <8808c9ac-0906-5eec-a31f-27cbec778f9c@intel.com> <5da90713-9a0d-6466-64f7-db435ba07dbe@intel.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, 18 Oct 2019, Xiaoyao Li wrote: > On 10/17/2019 8:29 PM, Thomas Gleixner wrote: > > The more I look at this trainwreck, the less interested I am in merging any > > of this at all. > > > > The fact that it took Intel more than a year to figure out that the MSR is > > per core and not per thread is yet another proof that this industry just > > works by pure chance. > > > > Whether it's per-core or per-thread doesn't affect much how we implement for > host/native. How useful. > And also, no matter it's per-core or per-thread, we always can do something in > VIRT. It matters a lot. If it would be per thread then we would not have this discussion at all. > Maybe what matters is below. > > > Seriously, this makes only sense when it's by default enabled and not > > rendered useless by VIRT. Otherwise we never get any reports and none of > > the issues are going to be fixed. > > > > For VIRT, it doesn't want old guest to be killed due to #AC. But for native, > it doesn't want VIRT to disable the #AC detection > > I think it's just about the default behavior that whether to disable the > host's #AC detection or kill the guest (SIGBUS or something else) once there > is an split-lock #AC in guest. > > So we can provide CONFIG option to set the default behavior and module > parameter to let KVM set/change the default behavior. Care to read through the whole discussion and figure out WHY it's not that simple? Thanks, tglx