From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751962AbeEMVzI (ORCPT ); Sun, 13 May 2018 17:55:08 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:51347 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750991AbeEMVzH (ORCPT ); Sun, 13 May 2018 17:55:07 -0400 Date: Sun, 13 May 2018 23:55:00 +0200 (CEST) From: Thomas Gleixner To: "Kirill A. Shutemov" cc: Ingo Molnar , x86@kernel.org, "H. Peter Anvin" , Hugh Dickins , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] x86/mm: Introduce 'no5lvl' kernel parameter In-Reply-To: <20180511120859.26375-3-kirill.shutemov@linux.intel.com> Message-ID: References: <20180511120859.26375-1-kirill.shutemov@linux.intel.com> <20180511120859.26375-3-kirill.shutemov@linux.intel.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 11 May 2018, Kirill A. Shutemov wrote: > --- a/arch/x86/kernel/cpu/common.c > +++ b/arch/x86/kernel/cpu/common.c > @@ -1008,6 +1008,12 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) > */ > setup_clear_cpu_cap(X86_FEATURE_PCID); > #endif > + > +#ifdef CONFIG_X86_5LEVEL > + /* Clear the 5-level paging feature if user asked for 'no5lvl' */ no5lvl is only one reason why 5 level paging is not available. > + if (!__pgtable_l5_enabled) > + setup_clear_cpu_cap(X86_FEATURE_LA57); > +#endif And that #ifdeffery can be avoided by simply doing: if (IS_ENABLED(CONFIG_X86_5LEVEL) && !pgtable_l5_enabled) setup_clear_cpu_cap(X86_FEATURE_LA57); Hmm? Thanks, tglx