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,URIBL_BLOCKED,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 243BBC432C3 for ; Wed, 13 Nov 2019 23:32:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8CB1D20643 for ; Wed, 13 Nov 2019 23:32:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726988AbfKMXb7 (ORCPT ); Wed, 13 Nov 2019 18:31:59 -0500 Received: from mga18.intel.com ([134.134.136.126]:1666 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726251AbfKMXb6 (ORCPT ); Wed, 13 Nov 2019 18:31:58 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 13 Nov 2019 15:31:57 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,302,1569308400"; d="scan'208";a="207609765" Received: from guptapadev.jf.intel.com (HELO guptapadev.amr) ([10.7.198.56]) by orsmga003.jf.intel.com with ESMTP; 13 Nov 2019 15:31:57 -0800 Date: Wed, 13 Nov 2019 15:25:10 -0800 From: Pawan Gupta To: Paolo Bonzini Cc: Jan Kiszka , 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: <20191113232510.GB891@guptapadev.amr> References: <1573593697-25061-1-git-send-email-pbonzini@redhat.com> <23353382-53ea-8b20-7e30-763ef6df374c@siemens.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Thanks, Pawan [1] https://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-vol-3b-part-2-manual.html