From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752538AbbABPzQ (ORCPT ); Fri, 2 Jan 2015 10:55:16 -0500 Received: from mail.emea.novell.com ([130.57.118.101]:58059 "EHLO mail.emea.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752388AbbABPzP convert rfc822-to-8bit (ORCPT ); Fri, 2 Jan 2015 10:55:15 -0500 Message-Id: <54A6BF5F02000078000C4AD1@mail.emea.novell.com> X-Mailer: Novell GroupWise Internet Agent 14.0.1 Date: Fri, 02 Jan 2015 15:55:11 +0000 From: "Jan Beulich" To: , , Cc: , Subject: Re: [Xen-devel] xen/x86: properly retrieve NMI reason References: <54945D760200007800051157@mail.emea.novell.com> <54994B7B.20309@citrix.com> In-Reply-To: <54994B7B.20309@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> David Vrabel 12/23/14 12:01 PM >>> >On 19/12/14 16:16, Jan Beulich wrote: >> Using the native code here can't work properly, as the hypervisor would >> normally have cleared the two reason bits by the time Dom0 gets to see >> the NMI (if passed to it at all). There's a shared info field for this, >> and there's an existing hook to use - just fit the two together. Note >> that the hook can (and should) be used irrespective of whether being in >> Dom0, as accessing port 0x61 in a DomU would be even worse, while the >> shared info field would just hold zero all the time. > >What's the user visible impact of this fix? Depends on what "user visible" is: It ought to prevent "Dazed and confused..." messages when not really applicable, and allow to get forwarded particularly SERR ones to APEI (GHES) code instead. I can't say I've seen this work in practice, as I lack ways to force SERR on otherwise well behaving hardware, but code inspection shows that the way it is now it can't work as intended. Jan