Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752757AbdL1AU4 (ORCPT ); Wed, 27 Dec 2017 19:20:56 -0500 Received: from mail.skyhub.de ([5.9.137.197]:36056 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751964AbdL1AUz (ORCPT ); Wed, 27 Dec 2017 19:20:55 -0500 Date: Thu, 28 Dec 2017 01:20:58 +0100 From: Borislav Petkov To: Tom Lendacky Cc: x86@kernel.org, Dave Hansen , linux-kernel@vger.kernel.org, Ingo Molnar , Andy Lutomirski , "H. Peter Anvin" , Thomas Gleixner Subject: Re: [PATCH] x86/cpu, x86/pti: Do not enable PTI on AMD processors Message-ID: <20171228001931.GA15868@nazgul.tnic> References: <20171227054354.20369.94587.stgit@tlendack-t1.amdoffice.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20171227054354.20369.94587.stgit@tlendack-t1.amdoffice.net> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1447 Lines: 39 On Tue, Dec 26, 2017 at 11:43:54PM -0600, Tom Lendacky wrote: > AMD processors are not subject to the types of attacks that the kernel > page table isolation feature protects against. The AMD microarchitecture > does not allow memory references, including speculative references, that > access higher privileged data when running in a lesser privileged mode > when that access would result in a page fault. > > Disable page table isolation by default on AMD processors by not setting > the X86_BUG_CPU_INSECURE feature, which controls whether X86_FEATURE_PTI > is set. > > Signed-off-by: Tom Lendacky > --- > arch/x86/kernel/cpu/common.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c > index c47de4e..7d9e3b0 100644 > --- a/arch/x86/kernel/cpu/common.c > +++ b/arch/x86/kernel/cpu/common.c > @@ -923,8 +923,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) > > setup_force_cpu_cap(X86_FEATURE_ALWAYS); > > - /* Assume for now that ALL x86 CPUs are insecure */ > - setup_force_cpu_bug(X86_BUG_CPU_INSECURE); > + if (c->x86_vendor != X86_VENDOR_AMD) > + setup_force_cpu_bug(X86_BUG_CPU_INSECURE); > > fpu__init_system(c); Reviewed-by: Borislav Petkov -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --