From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752126AbcCKTSc (ORCPT ); Fri, 11 Mar 2016 14:18:32 -0500 Received: from mail-wm0-f51.google.com ([74.125.82.51]:37272 "EHLO mail-wm0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751571AbcCKTS3 (ORCPT ); Fri, 11 Mar 2016 14:18:29 -0500 Subject: Re: runtime regression with "x86/mm/pat: Emulate PAT when it is disabled" To: Borislav Petkov , One Thousand Gnomes References: <1457393912.15454.419.camel@hpe.com> <20160307235328.GD26051@windriver.com> <1457398578.15454.421.camel@hpe.com> <1457400913.15454.435.camel@hpe.com> <20160310144250.GG23251@windriver.com> <1457628591.15454.542.camel@hpe.com> <20160310172029.GA2194@pd.tnic> <20160310190429.GI23251@windriver.com> <20160310191933.GC2194@pd.tnic> <20160311132356.43a7b373@lxorguk.ukuu.org.uk> <20160311134000.GC4347@pd.tnic> Cc: Paul Gortmaker , Toshi Kani , Richard Purdie , Toshi Kani , Bruce Ashfield , "Hart, Darren" , "saul.wold" , linux-kernel@vger.kernel.org, kvm ML , x86-ml From: Paolo Bonzini Message-ID: <56E319FF.3090709@redhat.com> Date: Fri, 11 Mar 2016 20:18:23 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <20160311134000.GC4347@pd.tnic> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/03/2016 14:40, Borislav Petkov wrote: > On Fri, Mar 11, 2016 at 01:23:56PM +0000, One Thousand Gnomes wrote: >> > Pentium Pro has MTRR, PAT came later. > Yep, this page says so too: > > http://www.cpu-world.com/CPUs/Pentium-II/Intel-Pentium%20Pro%20200%201%20MB%20-%20GJ80521EX200%201M%20%28BP80521200%201M%29.html > >> > I believe the qemu32 CPU isn't a "real" CPU type therefore. > And why is that so? I suspect it has again something to do with > migration and fun. Let me add the kvm ML. > > Guys, does anyone have an idea why > > #define PPRO_FEATURES (CPUID_FP87 | CPUID_DE | CPUID_PSE | CPUID_TSC | \ > CPUID_MSR | CPUID_MCE | CPUID_CX8 | CPUID_PGE | CPUID_CMOV | \ > CPUID_PAT | CPUID_FXSR | CPUID_MMX | CPUID_SSE | CPUID_SSE2 | \ > CPUID_PAE | CPUID_SEP | CPUID_APIC) > > has CPUID_PAT *instead* of CPUID_MTRR? Somebody got it wrong 10-ish years ago, and nobody has ever checked since. But, don't use qemu32 or qemu64. Use kvm32 and kvm64, or better something like the host you run on ("-cpu Nehalem", "-cpu SandyBridge", "-cpu Haswell-noTSX" etc.). I really, really should fix those defaults... Paolo