From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752941AbbLIIcP (ORCPT ); Wed, 9 Dec 2015 03:32:15 -0500 Received: from mail-wm0-f45.google.com ([74.125.82.45]:34575 "EHLO mail-wm0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751874AbbLIIcO (ORCPT ); Wed, 9 Dec 2015 03:32:14 -0500 Date: Wed, 9 Dec 2015 09:32:10 +0100 From: Ingo Molnar To: Dave Hansen Cc: the arch/x86 maintainers , LKML , "Yu, Yu-cheng" , "Yu, Fenghua" , Thomas Gleixner , "H. Peter Anvin" , Borislav Petkov Subject: Re: x86 fpu: command-line parameters broken post-FPU-rewrite Message-ID: <20151209083209.GB15254@gmail.com> References: <566740E1.40608@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <566740E1.40608@intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Dave Hansen wrote: > Hey Ingo, > > We were starting to look at reenabling XSAVES support and tried to use the > 'noxsave' and 'noxsaves' kernel command-line options. The rewrite moved the FPU > initialization to before we even are parsing command-line options, even the > early_param()s. > > Do you have any preferences on how it gets fixed? > > The most obvious thing would be to just defer as much of the FPU setup as we can > until after parse_early_param() has happened. The only other think I can think > of doing would be to try to do some *really* early, simple, command-line parsing > to look for 'noxsave' and friends. > > Thoughts? Hm, so given that having the FPU operational is key to a functioning kernel (and other kernel subsystems may make use of FPU functionality), I'd rather bring option parsing earlier than change the FPU setup sequence. FPU setup should be done when we identify the CPU - not 'very late' as we used to. Thanks, Ingo