From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751287AbdEBN0h (ORCPT ); Tue, 2 May 2017 09:26:37 -0400 Received: from mail-pg0-f65.google.com ([74.125.83.65]:32930 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751154AbdEBN0f (ORCPT ); Tue, 2 May 2017 09:26:35 -0400 Date: Tue, 2 May 2017 21:26:31 +0800 From: Wei Yang To: Wei Yang Cc: Borislav Petkov , tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/mm: trivial code cleanup for memory_map_top_doown() Message-ID: <20170502132631.GA7654@WeideMacBook-Pro.local> Reply-To: Wei Yang References: <20170217143033.95412-1-richard.weiyang@gmail.com> <20170313185021.oxl3ybuiiuqnyg5e@pd.tnic> <20170314035639.GA30208@WeideMacBook-Pro.local> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="BXVAT5kNtrzKuDFl" Content-Disposition: inline In-Reply-To: <20170314035639.GA30208@WeideMacBook-Pro.local> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --BXVAT5kNtrzKuDFl Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi, Borislav and all Do you agree with my analysis or you have other comments? On Tue, Mar 14, 2017 at 11:56:39AM +0800, Wei Yang wrote: >On Mon, Mar 13, 2017 at 07:50:21PM +0100, Borislav Petkov wrote: >>On Fri, Feb 17, 2017 at 10:30:33PM +0800, Wei Yang wrote: >>> In case (last_start <=3D step_size), start is for sure to be 0. So, it = is >> > >Hmm, I may write it more specific: > >"start" is for sure to be set to 0 with round_down(last_start - 1, step_si= ze). > >>Well, lemme see: >> >>[ 0.000000] memory_map_top_down: entry, [0x100000:0x7ffdf000) >>[ 0.000000] memory_map_top_down: addr: 0x7fc00000, real_end: 0x7fe00000 >>[ 0.000000] memory_map_top_down: last_start: 0x40000000 <=3D step_size= : 0x2000000000, start: 0x40000000 >> ^^^^^^^^^^ >>It doesn't look like 0 to me. >> >>--- >>diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c >>index 2193799ca800..d3b02a416df3 100644 >>--- a/arch/x86/mm/init.c >>+++ b/arch/x86/mm/init.c >>@@ -527,8 +531,13 @@ static void __init memory_map_top_down(unsigned long= map_start, >> start =3D round_down(last_start - 1, step_size); >> if (start < map_start) >> start =3D map_start; >>- } else >>+ } else { >>+ pr_info("%s: last_start: 0x%lx <=3D step_size: 0x%lx, start: 0x%lx\n", >>+ __func__, last_start, step_size, start); >>+ > >If you change this log with the following > > pr_err("%s: last_start: 0x%lx <=3D step_size: 0x%lx, start: 0x%lx\n", > __func__, last_start, step_size, > round_down(last_start - 1, step_size)); > >You could see after calculation, start is 0 when (last_start <=3D step_siz= e). > >--=20 >Wei Yang >Help you, Help me --=20 Wei Yang Help you, Help me --BXVAT5kNtrzKuDFl Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJZCIkGAAoJEKcLNpZP5cTdruEQAJr6NiKkvZjkeh/LUh4QMlPt mk211Us6rbnXwku2DDpM+25sqTlcMlrSQeRWjmJnz7S6Tka0f67KyaDHqxIHGwdN sc83xBlHT+H8eJ0mmvRAnEsZ+HKKkx+W6iXnbo2yO15+xphZUXTU2DXI3WWFows7 TOmp/nPtdHBP9ISO/k2OEfV7rONVYOKDQpSKVBEl5xWFzdCvP8m5Mhc1iM9SKu2c Jiwov0xEZHXu1BjCH4/Jq36st7r5AL1hbd4AF7KDR8GVu9v4ZdxXqTfDSt9IbRLh QLXigY7ZQcb/SPyGVcTNpgkMsPLlE+/TqzuvuVpGcgA83nJqIsXXG/3cSb2SDGgq UI3KjFXCM8phlK4jSBPnH2zHAp3x8ayxjCvI2Ms5YnzuGh6AcdCPTygyyekoT4KY GVPVEzx6XqcZHQLkSUnfCT/3fVubZvOs8Tsk/6PkhrlvmzlYqI+bRO+AGgzkhZ7I vx5aC94i5MPN7hlc/3/q9tyhwA6lchYsp+aTJKef9C6wFeyYyxDdz2JaFn6CroMw kad8AY4McA/o4Zg+mfTZ8QaMgiSnHt+Ym1RPl/SGln2+1krF1Y560+siTnqTTmWd 0rMKDoiJou8nVUKuhBmupnXGahYDQmkfKxv7LGOS5nJ2SDnNKHH8Ue/apJ1emsXZ 0/4OG+8Ek6KBMUrClDgH =swON -----END PGP SIGNATURE----- --BXVAT5kNtrzKuDFl--