From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from merlin.infradead.org ([205.233.59.134]:42897 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751411AbcEXJvo (ORCPT ); Tue, 24 May 2016 05:51:44 -0400 Date: Tue, 24 May 2016 11:51:24 +0200 From: Peter Zijlstra To: Borislav Petkov Cc: Andy Lutomirski , x86@kernel.org, Andi Kleen , linux-kernel@vger.kernel.org, Oleg Nesterov , stable@vger.kernel.org, Steven Rostedt Subject: Re: [PATCH] x86/traps: Don't for in_interrupt() to return true in IST handlers Message-ID: <20160524095124.GR3193@twins.programming.kicks-ass.net> References: <20160524085945.GE3192@twins.programming.kicks-ass.net> <20160524093629.GA2388@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160524093629.GA2388@pd.tnic> Sender: stable-owner@vger.kernel.org List-ID: @Andy, its linux-kernel@vger, not lkml@vger :-) On Tue, May 24, 2016 at 11:36:29AM +0200, Borislav Petkov wrote: > On Tue, May 24, 2016 at 10:59:45AM +0200, Peter Zijlstra wrote: > > Which use a sequence of: in_nmi(), in_irq(), in_softirq() to pick 1 out > > of 4 possible contexts. > > So should we make it cleaner and explicit and define a 5th context of > priorities higher than NMI? > > There's some room between those two: > > * NMI_MASK: 0x00100000 > * PREEMPT_NEED_RESCHED: 0x80000000 > A lot of pain; we'd have to go grow a whole bunch of things to 5. Also, I don't think 5 is enough to model all the IST nesting. I'm also not sure we really care too much; IST stuff is relatively rare. It just means we can loose IST based trace events and the like, because its treated as recursion. So I think keeping it at 4 is fine, but we do want to make a semi concious choice on how we map back to those 4.