Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752980AbeAGKf7 (ORCPT + 1 other); Sun, 7 Jan 2018 05:35:59 -0500 Received: from mail-ua0-f174.google.com ([209.85.217.174]:39811 "EHLO mail-ua0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752463AbeAGKf5 (ORCPT ); Sun, 7 Jan 2018 05:35:57 -0500 X-Google-Smtp-Source: ACJfBou0uXiBzzeNDLU/L3JzZ+IDFVQ+TjmDYcCDKKZ6nqjWGr6NT53AJcFR6QrWfCTZa/tqt2cXvOnWg5IWedW7Nr0= MIME-Version: 1.0 In-Reply-To: References: <20180106175059.19147-1-albcamus@gmail.com> From: Jike Song Date: Sun, 7 Jan 2018 18:35:56 +0800 Message-ID: Subject: Re: [PATCH] x86/mm/pti: remove dead logic during user pagetable population To: Thomas Gleixner Cc: luto@kernel.org, Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Sun, Jan 7, 2018 at 5:48 PM, Thomas Gleixner wrote: > On Sun, 7 Jan 2018, Jike Song wrote: >> On Sun, Jan 7, 2018 at 3:33 AM, Thomas Gleixner wrote: >> > On Sun, 7 Jan 2018, Jike Song wrote: >> > >> > Care to explain why you think this is not needed? >> > >> >> Hi Thomas, >> >> Look at one of the original code snippets: >> >> 162 if (pgd_none(*pgd)) { >> 163 unsigned long new_p4d_page = __get_free_page(gfp); >> 164 if (!new_p4d_page) >> 165 return NULL; >> 166 >> 167 if (pgd_none(*pgd)) { >> 168 set_pgd(pgd, __pgd(_KERNPG_TABLE | >> __pa(new_p4d_page))); >> 169 new_p4d_page = 0; >> 170 } >> 171 if (new_p4d_page) >> 172 free_page(new_p4d_page); >> 173 } >> >> Correct me if I'm too dumb to see the rationale here, but to me there >> can't be any difference between >> two pgd_none(*pgd) of L162 and L167, so it is always false in L171. > > Right, but this kind of explanation wants to be in the changelog. Empty > changelogs for this kind of change are just not acceptable. > Roger that, just sent v2 out :) I'm not quite sure but I CCed stable@kernel.org anyway. > Thanks, > > tglx -- Thanks, Jike