From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752771AbdI1Kk1 (ORCPT ); Thu, 28 Sep 2017 06:40:27 -0400 Received: from mail-wm0-f68.google.com ([74.125.82.68]:55242 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751830AbdI1KkJ (ORCPT ); Thu, 28 Sep 2017 06:40:09 -0400 X-Google-Smtp-Source: AOwi7QBKFBU4RYijpSdWRNKWjBip21APJKOf6imzwcTOa7woZ+YMtwQpwpESg/Ll82VZhaJP/rARSA== Date: Thu, 28 Sep 2017 12:40:05 +0200 From: Ingo Molnar To: "Kirill A. Shutemov" Cc: "Kirill A. Shutemov" , Ingo Molnar , Linus Torvalds , x86@kernel.org, Thomas Gleixner , "H. Peter Anvin" , Andrew Morton , Andy Lutomirski , Cyrill Gorcunov , Borislav Petkov , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv7 09/19] x86/mm: Make MAX_PHYSADDR_BITS and MAX_PHYSMEM_BITS dynamic Message-ID: <20170928104005.j23dwfkuycf2qqrk@gmail.com> References: <20170918105553.27914-1-kirill.shutemov@linux.intel.com> <20170918105553.27914-10-kirill.shutemov@linux.intel.com> <20170928082514.tl6tuigmx6oleus6@gmail.com> <20170928101736.oqbgmcbi2yp446hc@node.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170928101736.oqbgmcbi2yp446hc@node.shutemov.name> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Kirill A. Shutemov wrote: > On Thu, Sep 28, 2017 at 10:25:14AM +0200, Ingo Molnar wrote: > > > > * Kirill A. Shutemov wrote: > > > > > For boot-time switching between paging modes, we need to be able to > > > adjust size of physical address space at runtime. > > > > > > As part of making physical address space size variable, we have to make > > > X86_5LEVEL dependent on SPARSEMEM_VMEMMAP. !SPARSEMEM_VMEMMAP > > > configuration doesn't work well with variable MAX_PHYSMEM_BITS. > > > > > > Affect on kernel image size: > > > > > > text data bss dec hex filename > > > 10710340 4880000 860160 16450500 fb03c4 vmlinux.before > > > 10710666 4880000 860160 16450826 fb050a vmlinux.after > > > > > > Signed-off-by: Kirill A. Shutemov > > > --- > > > arch/x86/Kconfig | 1 + > > > arch/x86/include/asm/pgtable_64_types.h | 2 +- > > > arch/x86/include/asm/sparsemem.h | 9 ++------- > > > arch/x86/kernel/setup.c | 5 ++--- > > > 4 files changed, 6 insertions(+), 11 deletions(-) > > > > > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > > > index 6a15297140ff..f75723d62c25 100644 > > > --- a/arch/x86/Kconfig > > > +++ b/arch/x86/Kconfig > > > @@ -1403,6 +1403,7 @@ config X86_PAE > > > config X86_5LEVEL > > > bool "Enable 5-level page tables support" > > > depends on X86_64 > > > + depends on SPARSEMEM_VMEMMAP > > > > Adding a 'depends on' to random kernel internal implementational details, to > > support new hardware, sucks as an UI, as it will just randomly hide/show the new > > hardware option if certain magic Kconfig combinations are set. > > > > Please check how other architectures are doing it. (Hint: they are using select.) > > > > Also, what is the real dependency here? Why don't the other memory models work, > > what's the failure mode - won't build, won't boot, or misbehaves in some other > > way? > > I won't build. > > For !SPARSEMEM_VMEMMAP SECTIONS_WIDTH depends on MAX_PHYSMEM_BITS: > > SECTIONS_WIDTH > SECTIONS_SHIFT > MAX_PHYSMEM_BITS > > And SECTIONS_WIDTH is used on per-processor stage, it doesn't work if it's > dyncamic. See include/linux/page-flags-layout.h. Ok, this would be a good addition to the changelog. Thanks, Ingo