From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752179AbdK0NSw (ORCPT ); Mon, 27 Nov 2017 08:18:52 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:55102 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752094AbdK0NSu (ORCPT ); Mon, 27 Nov 2017 08:18:50 -0500 Date: Mon, 27 Nov 2017 14:18:44 +0100 (CET) From: Thomas Gleixner To: Brian Gerst cc: Peter Zijlstra , LKML , Dave Hansen , Andy Lutomirski , Ingo Molnar , Borislav Petkov , Denys Vlasenko , "H. Peter Anvin" , Josh Poimboeuf , Linus Torvalds , Rik van Riel , Daniel Gruss , Hugh Dickins , Kees Cook , Linux-MM , michael.schwarz@iaik.tugraz.at, moritz.lipp@iaik.tugraz.at, richard.fellner@student.tugraz.at Subject: Re: [patch V2 1/5] x86/kaiser: Respect disabled CPU features In-Reply-To: Message-ID: References: <20171126231403.657575796@linutronix.de> <20171126232414.313869499@linutronix.de> <20171127095737.ocolhqaxsaboycwa@hirez.programming.kicks-ass.net> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 27 Nov 2017, Brian Gerst wrote: > On Mon, Nov 27, 2017 at 6:47 AM, Thomas Gleixner wrote: > > On Mon, 27 Nov 2017, Peter Zijlstra wrote: > >> On Mon, Nov 27, 2017 at 12:14:04AM +0100, Thomas Gleixner wrote: > >> > PAGE_NX and PAGE_GLOBAL might be not supported or disabled on the command > >> > line, but KAISER sets them unconditionally. > >> > >> So KAISER is x86_64 only, right? AFAIK there is no x86_64 without NX > >> support. So would it not make sense to mandate NX for KAISER?, that is > >> instead of making "noexec" + KAISER work, make "noexec" kill KAISER + > >> emit a warning. > > > > OTOH, disabling NX is a simple way to verify that DEBUG_WX works correctly > > also on the shadow maps. > > > > But surely we can drop the PAGE_GLOBAL thing, as all 64bit systems have it. > > I seem to recall that some virtualized environments (maybe Xen?) don't > support global pages. Uuurg. Ok, we leave it as is for now. Better safe than sorry. It does no harm. Thanks, tglx From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id DD7096B0033 for ; Mon, 27 Nov 2017 08:19:16 -0500 (EST) Received: by mail-wm0-f72.google.com with SMTP id c82so4504182wme.8 for ; Mon, 27 Nov 2017 05:19:16 -0800 (PST) Received: from Galois.linutronix.de (Galois.linutronix.de. [2a01:7a0:2:106d:700::1]) by mx.google.com with ESMTPS id 93si21987493wrs.362.2017.11.27.05.19.15 for (version=TLS1_2 cipher=AES128-SHA bits=128/128); Mon, 27 Nov 2017 05:19:15 -0800 (PST) Date: Mon, 27 Nov 2017 14:18:44 +0100 (CET) From: Thomas Gleixner Subject: Re: [patch V2 1/5] x86/kaiser: Respect disabled CPU features In-Reply-To: Message-ID: References: <20171126231403.657575796@linutronix.de> <20171126232414.313869499@linutronix.de> <20171127095737.ocolhqaxsaboycwa@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Brian Gerst Cc: Peter Zijlstra , LKML , Dave Hansen , Andy Lutomirski , Ingo Molnar , Borislav Petkov , Denys Vlasenko , "H. Peter Anvin" , Josh Poimboeuf , Linus Torvalds , Rik van Riel , Daniel Gruss , Hugh Dickins , Kees Cook , Linux-MM , michael.schwarz@iaik.tugraz.at, moritz.lipp@iaik.tugraz.at, richard.fellner@student.tugraz.at On Mon, 27 Nov 2017, Brian Gerst wrote: > On Mon, Nov 27, 2017 at 6:47 AM, Thomas Gleixner wrote: > > On Mon, 27 Nov 2017, Peter Zijlstra wrote: > >> On Mon, Nov 27, 2017 at 12:14:04AM +0100, Thomas Gleixner wrote: > >> > PAGE_NX and PAGE_GLOBAL might be not supported or disabled on the command > >> > line, but KAISER sets them unconditionally. > >> > >> So KAISER is x86_64 only, right? AFAIK there is no x86_64 without NX > >> support. So would it not make sense to mandate NX for KAISER?, that is > >> instead of making "noexec" + KAISER work, make "noexec" kill KAISER + > >> emit a warning. > > > > OTOH, disabling NX is a simple way to verify that DEBUG_WX works correctly > > also on the shadow maps. > > > > But surely we can drop the PAGE_GLOBAL thing, as all 64bit systems have it. > > I seem to recall that some virtualized environments (maybe Xen?) don't > support global pages. Uuurg. Ok, we leave it as is for now. Better safe than sorry. It does no harm. Thanks, tglx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org