From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753568AbcD0PnS (ORCPT ); Wed, 27 Apr 2016 11:43:18 -0400 Received: from mail-oi0-f45.google.com ([209.85.218.45]:34160 "EHLO mail-oi0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753198AbcD0PfC (ORCPT ); Wed, 27 Apr 2016 11:35:02 -0400 MIME-Version: 1.0 In-Reply-To: <20160427153158.GJ21011@pd.tnic> References: <20160426225553.13567.19459.stgit@tlendack-t1.amdoffice.net> <20160426225604.13567.55443.stgit@tlendack-t1.amdoffice.net> <5720D066.7080409@amd.com> <5720D546.6050105@amd.com> <20160427153158.GJ21011@pd.tnic> From: Andy Lutomirski Date: Wed, 27 Apr 2016 08:34:42 -0700 Message-ID: Subject: Re: [RFC PATCH v1 01/18] x86: Set the write-protect cache mode for AMD processors To: Borislav Petkov Cc: Tom Lendacky , linux-arch , "linux-efi@vger.kernel.org" , kvm list , "linux-doc@vger.kernel.org" , X86 ML , "linux-kernel@vger.kernel.org" , kasan-dev , "linux-mm@kvack.org" , iommu@lists.linux-foundation.org, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Arnd Bergmann , Jonathan Corbet , Matt Fleming , Joerg Roedel , Konrad Rzeszutek Wilk , Paolo Bonzini , Ingo Molnar , "H. Peter Anvin" , Andrey Ryabinin , Alexander Potapenko , Thomas Gleixner , Dmitry Vyukov Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 27, 2016 at 8:31 AM, Borislav Petkov wrote: > On Wed, Apr 27, 2016 at 08:12:56AM -0700, Andy Lutomirski wrote: >> I think there are some errata > > Isn't that addressed by the first branch of the if-test in pat_init(): > > if ((c->x86_vendor == X86_VENDOR_INTEL) && > (((c->x86 == 0x6) && (c->x86_model <= 0xd)) || > ((c->x86 == 0xf) && (c->x86_model <= 0x6)))) { > That's the intent, but I'm unconvinced that it's complete. The reason that WT is in slot 7 is that if it accidentally ends up using the slot 3 entry instead of 7 (e.g. if a 2M page gets confused due to an erratum we didn't handle or similar), then it falls back to UC, which is safe. But this is mostly moot in this case. There is no safe fallback for WP, but it doesn't really matter, because no one will actually try to use it except on a system will full PAT support anyway. So I'm not really concerned. > > -- > Regards/Gruss, > Boris. > > ECO tip #101: Trim your mails when you reply. -- Andy Lutomirski AMA Capital Management, LLC