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=-2.2 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 84F42C432C3 for ; Fri, 15 Nov 2019 02:30:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 67B0020718 for ; Fri, 15 Nov 2019 02:30:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727089AbfKOCaS (ORCPT ); Thu, 14 Nov 2019 21:30:18 -0500 Received: from mga09.intel.com ([134.134.136.24]:52067 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727075AbfKOCaS (ORCPT ); Thu, 14 Nov 2019 21:30:18 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 14 Nov 2019 18:30:17 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,306,1569308400"; d="scan'208";a="199050528" Received: from guptapadev.jf.intel.com (HELO guptapadev.amr) ([10.7.198.56]) by orsmga008.jf.intel.com with ESMTP; 14 Nov 2019 18:30:17 -0800 Date: Thu, 14 Nov 2019 18:23:28 -0800 From: Pawan Gupta To: Jan Kiszka Cc: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Ralf Ramsauer , "Gupta, Pawan Kumar" Subject: Re: [FYI PATCH 0/7] Mitigation for CVE-2018-12207 Message-ID: <20191115022328.GC18745@guptapadev.amr> References: <1573593697-25061-1-git-send-email-pbonzini@redhat.com> <23353382-53ea-8b20-7e30-763ef6df374c@siemens.com> <20191113232510.GB891@guptapadev.amr> <671b49ab-f65d-8b44-4da6-137d05cd1b9c@siemens.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <671b49ab-f65d-8b44-4da6-137d05cd1b9c@siemens.com> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Nov 14, 2019 at 09:13:22AM +0100, Jan Kiszka wrote: > On 14.11.19 00:25, Pawan Gupta wrote: > > On Wed, Nov 13, 2019 at 09:23:30AM +0100, Paolo Bonzini wrote: > > > On 13/11/19 07:38, Jan Kiszka wrote: > > > > When reading MCE, error code 0150h, ie. SRAR, I was wondering if that > > > > couldn't simply be handled by the host. But I suppose the symptom of > > > > that erratum is not "just" regular recoverable MCE, rather > > > > sometimes/always an unrecoverable CPU state, despite the error code, right? > > > > > > The erratum documentation talks explicitly about hanging the system, but > > > it's not clear if it's just a result of the OS mishandling the MCE, or > > > something worse. So I don't know. :( Pawan, do you? > > > > As Dave mentioned in the other email its "something worse". > > > > Although this erratum results in a machine check with the same MCACOD > > signature as an SRAR error (0x150) the MCi_STATUS.PCC bit will be set to > > one. The Intel Software Developers manual says that PCC=1 errors are > > fatal and cannot be recovered. > > > > 15.10.4.1 Machine-Check Exception Handler for Error Recovery [1] > > > > [...] > > The PCC flag in each IA32_MCi_STATUS register indicates whether recovery > > from the error is possible for uncorrected errors (UC=1). If the PCC > > flag is set for enabled uncorrected errors (UC=1 and EN=1), recovery is > > not possible. > > > > And, as Dave observed, even that event is not delivered to software (maybe > just logged by firmware for post-reset analysis) but can or does cause a > machine lock-up, right? It can either cause a machine lock-up or a reset and the event delivery to the software is not guaranteed. Thanks, Pawan