From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753829AbYINIaN (ORCPT ); Sun, 14 Sep 2008 04:30:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751837AbYINI36 (ORCPT ); Sun, 14 Sep 2008 04:29:58 -0400 Received: from mx1.wp.pl ([212.77.101.5]:13779 "EHLO mx1.wp.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751794AbYINI34 (ORCPT ); Sun, 14 Sep 2008 04:29:56 -0400 Date: Sun, 14 Sep 2008 10:30:18 +0200 From: Krzysztof Helt To: "Yinghai Lu" Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com Subject: Re: [PATCH] x86: better CPU identification without the CPUID Message-Id: <20080914103018.f1d684a8.krzysztof.h1@wp.pl> In-Reply-To: <86802c440809132255sa518aa8g51136ae21a880e2d@mail.gmail.com> References: <20080913125606.d655bdcf.krzysztof.h1@wp.pl> <86802c440809132143p287edb82i6a73efbc53e6e93f@mail.gmail.com> <86802c440809132255sa518aa8g51136ae21a880e2d@mail.gmail.com> X-Mailer: Sylpheed 2.4.3 (GTK+ 2.11.0; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-WP-AV: skaner antywirusowy poczty Wirtualnej Polski S. A. X-WP-SPAM: NO 0000000 [AYP0] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 13 Sep 2008 22:55:10 -0700 "Yinghai Lu" wrote: > On Sat, Sep 13, 2008 at 9:43 PM, Yinghai Lu wrote: > > On Sat, Sep 13, 2008 at 3:56 AM, Krzysztof Helt wrote: > >> From: Krzysztof Helt > >> > >> cpus without the CPUID instruction are identified > >> as general 386 or 486 while some cpus (mostly made > >> by Cyrix) provide c_identify function which identify > >> correctly older cpus using cpu specific registers). > >> > >> Cyrix cpus are even worse as 5x86 and 6x68 have > >> the CPUID instruction disabled. The CPUID is > >> enabled by the c_identify() but the c_identify > >> is only called when the CPUID is available. > >> > >> Fix this by calling the c_identify() for all known > >> cpu families if there is no the CPUID instruction > > I updated it to tip/master and call that in early_identify_cpu. it > should solve mtrr detection for Cyrix ... > As I wrote I have no CPU to test this (Cyrix with ARRs). Finally, I am going to buy one or two of them during next two weeks so I will test. I would like to postpone your patch until I (or someone else) test it. There is some misunderstanding about the patch. There are two issues here. The early enabling of mtrr registers and nicer and more accurate /proc/cpuinfo content (and the CPU's name during boot). My patch was only about the latter. It was not about the early identification or solving the mtrr problem (as without testing I am not sure I can correctly do this). Your patch resets the /proc/cpuinfo content to the old status (before my patch). > From: "Yinghai Lu" > > [PATCH] x86: identify_cpu_without_cpuid > > need to call c_identify() for cpus without cpuid earlier... > > Signed-off-by: Yinghai Lu > /* > * Do minimum CPU detection early. > * Fields really needed: vendor, cpuid_level, family, model, mask, > @@ -503,18 +530,17 @@ static void __init early_identify_cpu(st > #endif > c->x86_cache_alignment = c->x86_clflush_size; > > - if (!have_cpuid_p()) > - return; > - > memset(&c->x86_capability, 0, sizeof c->x86_capability); > - > c->extended_cpuid_level = 0; > > - cpu_detect(c); > - > - get_cpu_vendor(c); > - > - get_cpu_cap(c); > + if (!have_cpuid_p()) { > + identify_cpu_without_cpuid(c); > + return; > + } else { > + cpu_detect(c); > + get_cpu_vendor(c); > + get_cpu_cap(c); > + } > > if (this_cpu->c_early_init) > this_cpu->c_early_init(c); One wants to call c_early_init() here for Cyrix cpus- otherwise the mtrr caps are not set. The correct patch here is only: - - if (!have_cpuid_p()) - return; - cpu_detect(c); + if (!have_cpuid_p()) + enable_cpuid_on_some_cpus(); /* pseudo code for now */ + if (have_cpuid_p()) + cpu_detect(c); The enabling of the cpuid instruction should be added there but only the enabling. > @@ -583,11 +609,13 @@ static void __cpuinit detect_nopl(struct > > static void __cpuinit generic_identify(struct cpuinfo_x86 *c) > { > - if (!have_cpuid_p()) > - return; > - I have just checked: http://git.kernel.org/?p=linux/kernel/git/x86/linux-2.6-tip.git and it differs here. It is the same as in my patch (who is out of sync?). > @@ -639,17 +667,6 @@ static void __cpuinit identify_cpu(struc > c->x86_cache_alignment = c->x86_clflush_size; > memset(&c->x86_capability, 0, sizeof c->x86_capability); > > - if (!have_cpuid_p()) { > - /* > - * First of all, decide if this is a 486 or higher > - * It's a 486 if we can modify the AC flag > - */ > - if (flag_is_changeable_p(X86_EFLAGS_AC)) > - c->x86 = 4; > - else > - c->x86 = 3; > - } > - > generic_identify(c); > > if (this_cpu->c_identify) The identify_cpu can stay the way it was. No changes here needed. My patch improves the /proc/cpuinfo content. The next patch should only enable the cpuid instruction on cyrix. Regards, Krzysztof