Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752668AbdLHRtB (ORCPT ); Fri, 8 Dec 2017 12:49:01 -0500 Received: from merlin.infradead.org ([205.233.59.134]:35570 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752100AbdLHRs5 (ORCPT ); Fri, 8 Dec 2017 12:48:57 -0500 Date: Fri, 8 Dec 2017 18:48:41 +0100 From: Peter Zijlstra To: Andy Lutomirski Cc: Ingo Molnar , Thomas Gleixner , Borislav Petkov , X86 ML , "linux-kernel@vger.kernel.org" , Brian Gerst , David Laight , Kees Cook Subject: Re: [PATCH] LDT improvements Message-ID: <20171208174841.ylx26jym5kpbrsta@hirez.programming.kicks-ass.net> References: <20171207124347.p7kdj7q4qqs3ivri@pd.tnic> <665F1CA8-D012-4465-B5F7-E81E088847DB@amacapital.net> <20171208073454.dicyefwncsihq7sm@gmail.com> <20171208094400.wqnezwukq5yx4mgq@gmail.com> <20171208113128.hdpeznolztrdzjpf@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 755 Lines: 19 On Fri, Dec 08, 2017 at 08:38:26AM -0800, Andy Lutomirski wrote: > 4. In an actual vma. I don't see the benefit of doing this at all -- > it's just like #2 except way more error prone. Hell, you have to make > sure that you can't munmap or mremap it, which isn't a consideration > at all with the other choices. mremap is trivially disabled. I've not tried munmap() yet, as long as it just kills the process doing it we're good of course. Otherwise we need an extra callback in do_munmap() which isn't too hard. > Why all the effort to make #4 work? Seemed like a sensible approach; I really dislike wasting an entire pmd or whatever on a feature 'nobody' ever uses anyway. > #1 is working fine right now doesn't work for pti in its current form.