From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752424AbYGXHHw (ORCPT ); Thu, 24 Jul 2008 03:07:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750832AbYGXHHq (ORCPT ); Thu, 24 Jul 2008 03:07:46 -0400 Received: from vpn.id2.novell.com ([195.33.99.129]:50259 "EHLO vpn.id2.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750817AbYGXHHq convert rfc822-to-8bit (ORCPT ); Thu, 24 Jul 2008 03:07:46 -0400 Message-Id: <4888467F.76E4.0078.0@novell.com> X-Mailer: Novell GroupWise Internet Agent 7.0.3 Date: Thu, 24 Jul 2008 08:08:15 +0100 From: "Jan Beulich" To: "Joerg Roedel" Cc: , "Andi Kleen" , , , Subject: Re: [PATCH] i386: improve double fault handling References: <4880A912.76E4.0078.0@novell.com> <20080723214320.GC13662@8bytes.org> In-Reply-To: <20080723214320.GC13662@8bytes.org> 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 >>> Joerg Roedel 23.07.08 23:43 >>> >On Fri, Jul 18, 2008 at 01:30:42PM +0100, Jan Beulich wrote: >> Make the double fault handler use CPU-specific stacks. Add some >> abstraction to simplify future change of other exception handlers to go >> through task gates. > >What is the benefit of exception handlers going through task gates? >Hardware task switches are not very well supported in virtualization >(e.g. its has issues in KVM and is also not in Xen for a long time). The main goal is to get to a different stack. While at present this is done only for the double fault, I think generally NMI and MCE should also do so, as they may be caused by a stack access (see x86-64, which runs them on IST stacks), and hence continuing to run on that same stack may not allow the exception to be handled. Jan