From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3110DC433F4 for ; Thu, 30 Aug 2018 13:15:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 62DA1205F4 for ; Thu, 30 Aug 2018 13:14:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 62DA1205F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728887AbeH3RRD (ORCPT ); Thu, 30 Aug 2018 13:17:03 -0400 Received: from mga06.intel.com ([134.134.136.31]:13225 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728273AbeH3RRC (ORCPT ); Thu, 30 Aug 2018 13:17:02 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Aug 2018 06:14:55 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,306,1531810800"; d="scan'208";a="84675121" Received: from shbuild888.sh.intel.com (HELO localhost) ([10.239.146.239]) by fmsmga004.fm.intel.com with ESMTP; 30 Aug 2018 06:14:53 -0700 Date: Thu, 30 Aug 2018 21:19:20 +0800 From: Feng Tang To: Thomas Gleixner Cc: Michal Hocko , Peter Zijlstra , linux-kernel@vger.kernel.org, x86@kernel.org, Ingo Molnar , "H . Peter Anvin" , Yinghai Lu , Dave Hansen , Andi Kleen Subject: Re: [PATCH] x86, mm: Reserver some memory for bootmem allocator for NO_BOOTMEM Message-ID: <20180830131920.w2jqjvlkpfb4ejb2@shbuild888> References: <20180830090319.985-1-feng.tang@intel.com> <20180830104401.GZ24124@hirez.programming.kicks-ass.net> <20180830111207.GE2656@dhcp22.suse.cz> <20180830124915.GH2656@dhcp22.suse.cz> <20180830125909.uq3e76akcmep6j2u@shbuild888> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Thomas, On Thu, Aug 30, 2018 at 03:05:31PM +0200, Thomas Gleixner wrote: > On Thu, 30 Aug 2018, Feng Tang wrote: > > On Thu, Aug 30, 2018 at 02:49:15PM +0200, Michal Hocko wrote: > > > On Thu 30-08-18 13:54:19, Thomas Gleixner wrote: > > > > On Thu, 30 Aug 2018, Michal Hocko wrote: > > > > > On Thu 30-08-18 12:44:02, Peter Zijlstra wrote: > > > > > > On Thu, Aug 30, 2018 at 05:03:19PM +0800, Feng Tang wrote: > > > > > > > The root cause is that when CONFIG_NO_BOOTMEM=y, before > > > > > > > e820__memblock_setup() is called there is no memory for bootmem > > > > > > > to allocate, > > > > > > > > > > > > Which you bloody well asked for by using NO_BOOTMEM=y. > > > > > > > > > > > > Going down this route; adding hacks for every little thing that does > > > > > > want bootmem, completely defeats the purpose. > > > > > > > > > > > > If anything, make the earlycon thing depend on NO_BOOTMEM=n. That also > > > > > > solves your problem. No earlycon, no panic. > > > > > > > > > > Well, there is endeavor to remove bootmem allocator altogether. So > > > > > making earlycon depend on NO_BOOTMEM=n doesn't sound like a good fit to > > > > > > > > If we want to remove bootmem, then reintroducing it with a static bootmem > > > > section doesn't make any sense at all. > > > > > > I have actually checked the code now and see what you mean. I thought it > > > would be a single allocation that is needed but that is not the case so > > > the static buffer is not going to fly. > > > > Exactly! I tried several ways for the static allocation, like in data, in bss > > section, but they all failed, as in the very start of setup_arch(): > > > > memblock_reserve(__pa_symbol(_text), > > (unsigned long)__bss_stop - (unsigned long)_text); > > > > Those [_text, __bss_stop] is not able to be used by alloc_bootmem(). And I > > only got this patch, and really appreciate any good suggestions. > > And why do you want to use bootmem in the first place? If boot mem is going > away, why are you not fixing the early console crap to NOT use bootmem at > all? The earlycon need use fixmap to map the mmio register, while fixmap will need a new page for page table if the pmd/pte is not already their, as shown in the commit log: panic+0xd2/0x220 __alloc_bootmem+0x31/0x34 spp_getpage+0x60/0x8a fill_pte+0x71/0x130 __set_pte_vaddr+0x1d/0x50 set_pte_vaddr+0x3c/0x60 __native_set_fixmap+0x23/0x30 native_set_fixmap+0x30/0x40 setup_earlycon+0x1e0/0x32f param_setup_earlycon+0x13/0x22 do_early_param+0x5b/0x90 parse_args+0x1f7/0x300 parse_early_options+0x24/0x28 parse_early_param+0x65/0x73 setup_arch+0x31e/0x9f1 start_kernel+0x58/0x44e inside the spp_getpage(): if (after_bootmem) ptr = (void *) get_zeroed_page(GFP_ATOMIC); else ptr = alloc_bootmem_pages(PAGE_SIZE); Thanks, Feng