Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754463AbcLOUxo (ORCPT ); Thu, 15 Dec 2016 15:53:44 -0500 Received: from terminus.zytor.com ([198.137.202.10]:37976 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753728AbcLOUxm (ORCPT ); Thu, 15 Dec 2016 15:53:42 -0500 User-Agent: K-9 Mail for Android In-Reply-To: <20161215192017.GP8388@tassilo.jf.intel.com> References: <20161208162150.148763-1-kirill.shutemov@linux.intel.com> <20161208162150.148763-17-kirill.shutemov@linux.intel.com> <20161208200505.c6xiy56oufg6d24m@pd.tnic> <20161208202013.uutsny6avn5gimwq@pd.tnic> <20161215143944.ruxr6r3b2atg4tnf@pd.tnic> <20161215190902.tdle4uj27xkc3x4i@pd.tnic> <20161215192017.GP8388@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Subject: Re: [RFC, PATCHv1 15/28] x86: detect 5-level paging support From: hpa@zytor.com Date: Thu, 15 Dec 2016 12:52:24 -0800 To: Andi Kleen , Borislav Petkov CC: Linus Torvalds , "Kirill A. Shutemov" , Andrew Morton , the arch/x86 maintainers , Thomas Gleixner , Ingo Molnar , Arnd Bergmann , Dave Hansen , Andy Lutomirski , "linux-arch@vger.kernel.org" , linux-mm , Linux Kernel Mailing List Message-ID: <43EC6ED8-445E-436C-AC05-A2C7CB3AD9E7@zytor.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 571 Lines: 13 On December 15, 2016 11:20:17 AM PST, Andi Kleen wrote: > >The code is not calling CPUID in any performance critical path, only >at initialization. So any discussion about saving a few instructions >is a complete waste of time. > >-Andi Sort of. The BIOS boot code is very space-constrained for certain legacy bootloaders to continue to work. The BIOS boot code proper does not need PIC. However, the existing .ifnc solution already takes care of it, so it doesn't matter. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.