Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932105AbeAHUt0 (ORCPT + 1 other); Mon, 8 Jan 2018 15:49:26 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:50975 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751597AbeAHUtZ (ORCPT ); Mon, 8 Jan 2018 15:49:25 -0500 Date: Mon, 8 Jan 2018 21:49:23 +0100 (CET) From: Thomas Gleixner To: Willy Tarreau cc: Linus Torvalds , Linux Kernel Mailing List , the arch/x86 maintainers , One Thousand Gnomes , Andy Lutomirski Subject: Re: [PATCH RFC 2/4] x86/arch_prctl: add ARCH_GET_NOPTI and ARCH_SET_NOPTI to enable/disable PTI In-Reply-To: <20180108182234.GL10913@1wt.eu> Message-ID: References: <1515427939-10999-1-git-send-email-w@1wt.eu> <1515427939-10999-3-git-send-email-w@1wt.eu> <20180108182234.GL10913@1wt.eu> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Mon, 8 Jan 2018, Willy Tarreau wrote: > On Mon, Jan 08, 2018 at 09:54:05AM -0800, Linus Torvalds wrote: > > > So make the thing per-mm, and then at task switch time as you switch > > mms, you set the bit in a percpu variable for testing at kernel entry. > > I'll see how to do that, this is not yet 100% clear to me, I'm still > discovering (this code has immensely changed since last time I *really* > dug into it). So I suspect I'll have to set this variable in > __switch_to() based on this other MM flag. The right thing is probably the cpu entry area because that's what you can access before switching CR3 if PTI is enabled for the task Thanks, tglx