From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753385AbdI1NTP (ORCPT ); Thu, 28 Sep 2017 09:19:15 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:38023 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753228AbdI1NTN (ORCPT ); Thu, 28 Sep 2017 09:19:13 -0400 X-Google-Smtp-Source: AOwi7QBaxeH8SxQOlfEhREBSPXxKJcp6ujbfhpBGWwGInF8AM3InWg9XJYXycgrZ1vcP/9YrQIv5mQ== Date: Thu, 28 Sep 2017 16:19:10 +0300 From: "Kirill A. Shutemov" To: Ingo Molnar 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 11/19] x86/mm: Make STACK_TOP_MAX dynamic Message-ID: <20170928131910.7t7ops6b7h7fcrmm@node.shutemov.name> References: <20170918105553.27914-1-kirill.shutemov@linux.intel.com> <20170918105553.27914-12-kirill.shutemov@linux.intel.com> <20170928082955.n7t4wlz7olsgwkfn@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170928082955.n7t4wlz7olsgwkfn@gmail.com> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 28, 2017 at 10:29:55AM +0200, Ingo Molnar wrote: > > * Kirill A. Shutemov wrote: > > > For boot-time switching between paging modes, we need to be able to > > change STACK_TOP_MAX at runtime. > > > > The change is trivial and it doesn't affect kernel image size. > > > > Signed-off-by: Kirill A. Shutemov > > --- > > arch/x86/include/asm/processor.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h > > index 3fa26a61eabc..fa9300ccce1b 100644 > > --- a/arch/x86/include/asm/processor.h > > +++ b/arch/x86/include/asm/processor.h > > @@ -871,7 +871,7 @@ static inline void spin_lock_prefetch(const void *x) > > IA32_PAGE_OFFSET : TASK_SIZE_MAX) > > > > #define STACK_TOP TASK_SIZE_LOW > > -#define STACK_TOP_MAX TASK_SIZE_MAX > > +#define STACK_TOP_MAX (pgtable_l5_enabled ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW) > > While it's only used once in fs/exec.c, why doesn't it affect kernel image size? Oh. After closer look the patch is redundant. The STACK_TOP_MAX is already dynamic due to dynamic TASK_SIZE_MAX, so gcc generates exactly the same code before and after the patch. I'll drop it. -- Kirill A. Shutemov