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=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 57C69C433F5 for ; Thu, 30 Aug 2018 11:12:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1551A2054F for ; Thu, 30 Aug 2018 11:12:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1551A2054F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 S1728574AbeH3PNs (ORCPT ); Thu, 30 Aug 2018 11:13:48 -0400 Received: from mx2.suse.de ([195.135.220.15]:36558 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728261AbeH3PNr (ORCPT ); Thu, 30 Aug 2018 11:13:47 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 6D6DEACC6; Thu, 30 Aug 2018 11:12:09 +0000 (UTC) Date: Thu, 30 Aug 2018 13:12:07 +0200 From: Michal Hocko To: Peter Zijlstra Cc: Feng Tang , linux-kernel@vger.kernel.org, x86@kernel.org, Thomas Gleixner , 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: <20180830111207.GE2656@dhcp22.suse.cz> References: <20180830090319.985-1-feng.tang@intel.com> <20180830104401.GZ24124@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180830104401.GZ24124@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 30-08-18 12:44:02, Peter Zijlstra wrote: > On Thu, Aug 30, 2018 at 05:03:19PM +0800, Feng Tang wrote: > > We hit a kernel panic when enabling earlycon for a platform, the > > call trace is: > > > > 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 > > > > 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 me. I am not familiar with this code path but why cannot we postpone the allocation to later or use a statically allocated storage? -- Michal Hocko SUSE Labs