Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1758621AbcLBAdk (ORCPT <rfc822;w@1wt.eu>);
        Thu, 1 Dec 2016 19:33:40 -0500
Received: from mail-ua0-f179.google.com ([209.85.217.179]:32813 "EHLO
        mail-ua0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1756277AbcLBAdi (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 1 Dec 2016 19:33:38 -0500
MIME-Version: 1.0
In-Reply-To: <20161201090211.nrlyjt5uklcva3pd@pd.tnic>
References: <cover.1480536936.git.luto@kernel.org> <56690623af05784f41a4efbe1b25b1e2c43fdefb.1480536936.git.luto@kernel.org>
 <20161201055350.GH3092@twins.programming.kicks-ass.net> <20161201090211.nrlyjt5uklcva3pd@pd.tnic>
From: Andy Lutomirski <luto@amacapital.net>
Date: Thu, 1 Dec 2016 16:33:17 -0800
Message-ID: <CALCETrWzCH7n7zqs278-mXiceP9jjt6T+ZkLhdqa05kGg7QHbQ@mail.gmail.com>
Subject: Re: [PATCH 2/4] Revert "x86/boot: Fail the boot if !M486 and CPUID is missing"
To: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
        One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Brian Gerst <brgerst@gmail.com>,
        Matthew Whitehead <tedheadster@gmail.com>,
        Henrique de Moraes Holschuh <hmh@hmh.eng.br>,
        Denys Vlasenko <dvlasenk@redhat.com>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 948
Lines: 21

On Thu, Dec 1, 2016 at 1:02 AM, Borislav Petkov <bp@alien8.de> wrote:
> On Thu, Dec 01, 2016 at 06:53:50AM +0100, Peter Zijlstra wrote:
>> On Wed, Nov 30, 2016 at 12:34:53PM -0800, Andy Lutomirski wrote:
>> > This reverts commit ed68d7e9b9cfb64f3045ffbcb108df03c09a0f98.
>> >
>> > The patch wasn't quite correct -- there are non-Intel (and hence
>> > non-486) CPUs that we support that don't have CPUID.  Since we no
>> > longer require CPUID for sync_core(), just revert the patch.
>>
>> Might be useful to enumerate which special parts these are.
>
> Right, and since we test for CPUID support at early boot, I think we
> should use the X86_FEATURE_CPUID aspect from what I proposed earlier:
>
> https://lkml.kernel.org/r/20161120111917.pw3alolx4fksfwbv@pd.tnic

Maybe we should just make the kernel work fully without CPUID.  There
isn't much to do on top of your patch -- I think we mainly want to
make the cpuid driver refuse to load.

--Andy