Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754099AbbGWVfN (ORCPT ); Thu, 23 Jul 2015 17:35:13 -0400 Received: from mail-ig0-f173.google.com ([209.85.213.173]:37727 "EHLO mail-ig0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753682AbbGWVfJ (ORCPT ); Thu, 23 Jul 2015 17:35:09 -0400 MIME-Version: 1.0 In-Reply-To: <20150723212042.GN25159@twins.programming.kicks-ass.net> References: <20150723212042.GN25159@twins.programming.kicks-ass.net> Date: Thu, 23 Jul 2015 14:35:08 -0700 X-Google-Sender-Auth: aQvqMWKRWAC-pdBc9n6CKsOxL2Q Message-ID: Subject: Re: Dealing with the NMI mess From: Linus Torvalds To: Peter Zijlstra Cc: Andy Lutomirski , X86 ML , "linux-kernel@vger.kernel.org" , Willy Tarreau , Borislav Petkov , Thomas Gleixner , Steven Rostedt , Brian Gerst Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1011 Lines: 24 On Thu, Jul 23, 2015 at 2:20 PM, Peter Zijlstra wrote: > > So the NMI could trigger userspace debug register faults, and simply > disabling them would make the whole debug register thing entirely > unreliable. We could easily set something to re-enable them for when we actually return to user space. I'd be ok with just setting the _TIF_USER_WORK_MASK. But even that should not be a requirement for the basic stability and core integrity of the kernel. Not like the current horrid mess with NMI nesting and ESP fixing etc. And realistically, nobody will ever even notice. So the whole "ok, we can use _TIF_USER_WORK_MASK to re-enable dr7" is a tiny tiny detail that is more like cleaning up things, not a core issue. Linus -- 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/