Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756979AbaDVTzR (ORCPT ); Tue, 22 Apr 2014 15:55:17 -0400 Received: from mail-la0-f49.google.com ([209.85.215.49]:44898 "EHLO mail-la0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756937AbaDVTzN (ORCPT ); Tue, 22 Apr 2014 15:55:13 -0400 MIME-Version: 1.0 In-Reply-To: <5356BA2F.2030007@zytor.com> References: <20140422112312.GB15882@pd.tnic> <20140422144659.GF15882@pd.tnic> <53569467.1030809@zytor.com> <5356A70A.5090907@zytor.com> <5356AF9F.4010301@zytor.com> <5356BA2F.2030007@zytor.com> Date: Tue, 22 Apr 2014 15:55:11 -0400 Message-ID: Subject: Re: [PATCH] x86-64: espfix for 64-bit mode *PROTOTYPE* From: Brian Gerst To: "H. Peter Anvin" Cc: Andrew Lutomirski , Linus Torvalds , Borislav Petkov , "H. Peter Anvin" , Linux Kernel Mailing List , Ingo Molnar , Alexander van Heukelum , Konrad Rzeszutek Wilk , Boris Ostrovsky , Arjan van de Ven , Alexandre Julliard , Andi Kleen , Thomas Gleixner Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 22, 2014 at 2:51 PM, H. Peter Anvin wrote: > On 04/22/2014 11:17 AM, Brian Gerst wrote: >>> >>> That is the entry condition that we have to deal with. The fact that >>> the switch to the IST is unconditional is what makes ISTs hard to deal with. >> >> Right, that is why you switch away from the IST as soon as possible, >> copying the data that is already pushed there to another stack so it >> won't be overwritten by a recursive fault. >> > > That simply will not work if you can take a #GP due to the "safe" MSR > functions from NMI and #MC context, which would be my main concern. In that case (#2 above), you would switch to the previous %rsp (in the NMI/MC stack), copy the exception frame from the IST, and continue with the #GP handler. That effectively is the same as it is today, where no stack switch occurs on the #GP fault. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/