Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753168AbeADTGu (ORCPT + 1 other); Thu, 4 Jan 2018 14:06:50 -0500 Received: from mail.skyhub.de ([5.9.137.197]:51878 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751679AbeADTGr (ORCPT ); Thu, 4 Jan 2018 14:06:47 -0500 Date: Thu, 4 Jan 2018 20:06:45 +0100 From: Borislav Petkov To: Dave Hansen Cc: Tim Chen , Thomas Gleixner , Andy Lutomirski , Linus Torvalds , Greg KH , Andrea Arcangeli , Andi Kleen , Arjan Van De Ven , linux-kernel@vger.kernel.org Subject: Re: [PATCH 6/7] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature Message-ID: <20180104190645.poukc46fbwtwevby@pd.tnic> References: <4d4b3752e8e533201c6983d8473eea95c747ea33.1515086770.git.tim.c.chen@linux.intel.com> <20180104183345.od2o4hsfu2tv6nc4@pd.tnic> <20180104185219.wji527snw6xzggak@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 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 Return-Path: On Thu, Jan 04, 2018 at 10:59:35AM -0800, Dave Hansen wrote: > On 01/04/2018 10:52 AM, Borislav Petkov wrote: > >> Paranoid people want "IBRS always" aka "ibrs 2". > > > > So why not "IBRS always" or off? No need for the "IBRS only in the > > kernel" setting. > > IBRS=1 slows execution down. If it's on all the time, you pay a > performance cost in userspace. The assumption is that the user/kernel > boundary switching cost is below the cost of having it on all the time. Ok, so we need to make this distinction visible to users so that they are aware. Also, adding a common, combined option which is called something like make_my_kernel_supa_dupa_secure or so would make sense too, for all those paranoid people. Because I see the mess coming: ibrs= ibpb= pti= ... A helluva confusion that would be. Thx. -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.