Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753574AbbGXP1V (ORCPT ); Fri, 24 Jul 2015 11:27:21 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:9444 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751895AbbGXP1T (ORCPT ); Fri, 24 Jul 2015 11:27:19 -0400 Date: Fri, 24 Jul 2015 17:26:37 +0200 From: Willy Tarreau To: Steven Rostedt Cc: Peter Zijlstra , Linus Torvalds , Andy Lutomirski , X86 ML , "linux-kernel@vger.kernel.org" , Borislav Petkov , Thomas Gleixner , Brian Gerst Subject: Re: Dealing with the NMI mess Message-ID: <20150724152637.GC3612@1wt.eu> References: <20150724081326.GO25159@twins.programming.kicks-ass.net> <20150724075841.40f209f4@gandalf.local.home> <20150724124304.GH19282@twins.programming.kicks-ass.net> <20150724090342.6d11e16d@gandalf.local.home> <20150724132128.GA3612@1wt.eu> <20150724103127.3c3f4693@gandalf.local.home> <20150724145901.GB3612@1wt.eu> <20150724111621.34713023@gandalf.local.home> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150724111621.34713023@gandalf.local.home> User-Agent: Mutt/1.4.2.3i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1301 Lines: 35 On Fri, Jul 24, 2015 at 11:16:21AM -0400, Steven Rostedt wrote: > On Fri, 24 Jul 2015 16:59:01 +0200 > Willy Tarreau wrote: > > > On Fri, Jul 24, 2015 at 10:31:27AM -0400, Steven Rostedt wrote: > > > On Fri, 24 Jul 2015 15:21:28 +0200 > > > Willy Tarreau wrote: > > > > > > > My understanding is that by using RET we can't set the RF flag and #DB > > > > > > But the RF flag is only set for instruction (executing) breakpoints. It > > > is not set for data (RW) ones. > > > > True but these also are the most complicated to deal with. The data > > accesses can always be emulated (not what I'm suggesting here) while > > instructions are much harder to emulate. > > The point is, if we trigger a #DB on an instruction breakpoint > while !IF, then we simply disable that breakpoint and do the RET. Yes but the breakpoint remains disabled then. Or I'm missing something. > What emulation is needed? I was speaking about redoing the operation with BP disabled before re-enabling it. But that's not the point here anyway. Willy -- 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/